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Greenhouse germination and seedling propagation method studies in the improvement of some forage grasses

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TITLE
Greenhouse Germination and Seedling Propagation
Method Studies in the Improvement of Some Forage Grasses.
BY
Laurence Cutler Newell
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SUPERVISORY COMMITTEE
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GREENHOUSE GERMINATION AND SEEDLING PROPAGATION
METHOD STUDIES
in the
IMPROVEMENT 01 SOME FORAGE GRASSES
hy
Laurence Cutler Newell
A THESIS
Presented to the Faculty o f
The Graduate College in the U niversity of Nebraska
In P artial Fulfillm ent o f Requirements
Fbr the Degree o f Doctor of Philosophy
Department o f Agronomy
Lincoln, Nebraska
May, 19*10
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U M I N um ber: D P 1 4 1 2 4
IN F O R M A T IO N T O U S E R S
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®
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unauthorized copying un d er Title 17, United S ta te s C ode.
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CONTENTS
f<T ^
INTRODUCTION........................................................................................
V;
- 5,.
« V ADAPTATION OP SPECIES TO 5HE REGION.........................................
;;
FIELD ENVIRONMENT................................................................ ...
GREENHOUSE ENVIRONMENT ....................................................................
MATERIALS AND METHODS....................................................................
Introduced and Native G ra sse s................ ............................
Seed G erm in ation ................ ... ................................................
Soil f l a t s and Paper Bands ................ .............................
Soil Mixtures and S t e r iliz a t io n .................................... ...
Spotting and Transplanting .
........................................
EXPERIMENTAL RESULTS........................................................................
Germination Methods . ................................. . . . . . . .
E ffects of s o il s te r iliz a tio n .................................
E ffects o f kind of s o il
...................... . .
E ffects of d ifferen t temperatures .........................
Germination Studies with Eighteen Species . . . . . .
L
C5
nr
o
©
j
d
Mi
Seed germination of the cool-temperature grasses
Seed germination of the warm-temperature grasses
Dormancy of grass seeds
E ffects of refrigeration and chemical treatment
Seedling Establishment and Growth . . . . . .
E ffects of plant hands and s o il mixtures
E ffects of temperature and lig h t . . . .
Advantages and disadvantages of spotting
Seeding and Transplanting S ea so n s......................
F ield Establishment . . . . . . . . . . . . .
V ia b ility of Stored seed
o
.....................................
SUMMARY ........................................................................................
LITERATURE CITED................................................ ....
GRAPHS ............................................................................................
372031
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ACKNOWLEDGMENT
Bie writer wishes to express h is appreciation to the Bureau of Plant
Industry, U. S* Department of Agriculture and to the Department of Agron­
omy, Nebraska A gricultural Experiment Station, for permission to use data
obtained in the course o f development of a program o f cooperative grass
improvement in vestigation s conducted a t the Nebraska Agriculural Experi­
ment Station,
She writer i s esp ecia lly indebted to Dr, E, D* Keim, Chair­
man of the Department of Agronomy, who was largely responsible for making
th is program and study p ossib le; to Dr, A. L. Erolik of the same depart­
ment, and to Mr. E. C, Conard o f the Soil Conservation Service Nurseries,
U. S. Department of Agriculture, for helpful suggestions and assistance
throughout the course of the work; and to Mr. E, C. Conard for making
available certain seed supplies o f native grasses,
The writer i s further
indebted to Mr. Maurice M iller, A ssistant in Agronomy, for the photography
of the graphs.
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Greenhouse Germination and Seedling Propagation Method
Studies in the Improvement o f some Forage Grasses
IIlRODUCflON
The purpose o f th is b u lletin i s to present the r e su lts o f method stu dies
on the problems involved in the growing o f grass seedlings in the greenhouse
for transplanting to the f ie ld .
Bie b u lle tin describes the methods o f green­
house culture as developed a t the Nebraska Agricultural Experiment Station.
She broad objectives o f the grass in vestigation s are file development o f im­
proved strain s o f the most promising introduced and native grasses and the
te s tin g of these species and strain s to determine th eir adaptation to vary­
ing environmental conditions and to d ifferen t u ses.
She work o f forage grass breeding i s r e la tiv e ly new.
Most o f the breed­
ing work with perennial grasses in the United States has been confined to
those introduced grasses best adapted to the cool clim ates of the north­
eastern and northern sta te s.
A few of these o ffer much promise for improve­
ment and adaptation to other regions.
L ittle has been done in the selection
and improvement o f perennial grasses native to the large areas o f grasslands
in th is country.
The p o s s ib ilit ie s of improving some o f these native grasses
for cu ltivation was noted by workers in the U. S. Department o f Agriculture
during the early part o f the present century.
A review o f th eir observations
on some o f these species has bean included in a b u lle tin by Savage (19) ^ •
Nothing came out o f the early in te r e st in bringing the p ra irie grasses under
cu ltivation because the better grasslands were at that time being broken for
cash crop production,
A new valuation i s now being placed upon grass.
—I Refers to lite ra tu re c ited .
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Its
2
greater use as a farm crop awaits the selectio n of adapted desirable species
and strain s which w ill control erosion, furnish a reasonable production o f
forage,and provide an adequate seed supply which can be handled at reason­
able prices*
A t t e s t s a t securing native-grass seed in large q u an tities were re­
newed by government agencies in 193^ and 1935*
Machine harvesting of seed
from native meadows and pastures o f northern and western Nebraska was con­
ducted by the S oil Conservation Service Nurseries in 1935*
Seed o f a number
o f species was obtained in large q u an tities, to ta lin g approximately 30*000
pounds.
In addition, nearly h a lf a m illion pounds o f western wheatgrass
(Agro-pyron sm ith!l) were harvested in South Dakota*
Similar a c tiv itie s
have been conducted in a number of sta te s o f the Great P lains since those
years.
Methods o f harvesting native-grass seeds have been described by
F ults (11) and by Crider and Hoover (7 ).
In developing a program o f improvement of forage grasses, some o f
which have not been brought under extensive c u ltiv a tio n , atten tion should
be given to studies o f methods o f procedure*
Ihe f i r s t task i s that o f a
provisional selectio n o f species and regionally produced strain s best ad­
apted for certain environments as indicated by preliminary t r i a l s .
Where
seed lo t s are large enough, these t r ia ls may be in short row or block
p lan tin gs.
Elimination o f unadapted material can soon be made.
Having
selected the sources o f the best breeding m aterial, the next problem is
that o f determining methods o f culture by which a regular succession o f
generations o f plant material can be secured, and i t s breeding behavior
studied,
ttie use o f a greenhouse for the growing of seedlings for trans­
planting to the f ie ld has been found indispensable to such a program of
grass breeding.
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Greenhouse seedling propagation i s p articu larly important in regions
where clim atic conditions make hazardous the regular annual establishment
o f stands o f small-seeded grasses by seeding methods.
Seed supplies o f
valuable se lectio n s are often very small* because some forage types eith er
produce l i t t l e seed or are not found In abundance.
Seed lo t s of intro­
ductions from other sta tes and countries, and the remnants o f seed from
previous plantings which prove valuable, are frequently handled in small
quantities*
transplanting of seedlings grown in the greenhouse insures
the uniform establishment of space-planted plan ts of such small seed l o t s ,
the greenhouse production of seedlings i s p articu larly important from a
breeding standpoint because of the n ecessity of securing maximum germina­
tion and care o f the resu ltin g plant progenies o f selfed or open-pollinated
seed o f sin gle-p lan t se le c tio n s.
there seed supplies o f adapted strains are abundant, i t i s desirable
to transplant to the f ie ld a large number of space-planted individuals to
observe and to s e le c t for forage q u ality, seed production, or disease re­
sista n ce.
She superior p la n ts, once found and tested by their progeny
( 17) , may be used for a number of years for making various combinations
in the breeding o f superior v a r ie tie s .
Preliminary work in the spring o f l $ j 6 presented a number o f problems
o f greenhouse culture.
D iffic u ltie s
were e n c o u n te re d , in s e c u r i n g suitable
establishment o f seedlings o f several sp ecies, due eith er to seed dormancy
or to seedling d isea ses.
The responses o f seed germination and seedling
growth to temperature were not known.
The proper time and su itab le methods
o f transplanting seedlings to the f ie ld had not been determined.
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Since.
k
knowledge o f the behavior of the plant material i s e sse n tia l to the breeder,
i t seemed desirable to conduct experiments to evaluate some of the problems*
Germination studies were made to determine the effectiv en ess o f s o il
s te r iliz a tio n in increasing seed germination and seedling establishment*
Seed lo t s o f IS species o f grasses were tested a t monthly in tervals to
learn the time o f maximum germination and seedling vigor o f the seed lo t s
during a four year period a fter harvest*
A number o f seed treatments were
tried to induce germination o f dormant seeds*
A study was made of seedling
growth as produced by d ifferen t siz e s of containers and by s o il mixtures o f
d ifferen t degrees o f f e r t i l i t y .
Bata was secured to determine the best
times for germinating the seed and for transplanting the seedlings to the
f ie ld as related to su rvival.
With the observations and data secured
during four years, i t was p ossib le to formulate plans for the advantageous
use o f greenhouse space in the handling of grasses with d ifferen t growth
habits*
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5
ADAPTATION OP SFSCHS TO THE HEGION
She region to which th is study pertains i s that o f the eastern part
o f the Central Great P lains.
A large number of grasses are adapted to the
varying s o il and clim atic conditions within the borders of th is region.
She eastern one-third o f Nebraska and territory extending eastward
into Iowa, northward into eastern Soulh Dakota, and southward into eastern
Kansas i s made up of farm lands broken from the original true p r a irie.
Only small acreages of th is origin al climax vegetation remain in the form
o f hay meadows and pasture areas which have suffered from the e ffe c ts of
continued drought and the la tte r from serious overgrazing.
The ecology
o f the true p rairie sp ecies as determined prior to the drought o f I93U
has been described by Weaver and F itzpatrick (29).
The v ia b ilit y of seeds
and early l i f e h istory of p ra irie plants of th is region have been studied
by H ake (6) .
Extending westward from the true p rairie to the mountains,
the grass species of the mixed p ra irie form the climax vegetation.
Bae
relation sh ip s of these species in the mixed p rairie have been studied by
Albertson (1 ).
The far-reaching e ffe c ts of drought on the native vege­
tation of these grassland associations have been described by Weaver,
Stoddart, and N oll (30), and Weaver and Albertson ( 26, 27).
The eastern one-third o f Nebraska may be considered as a sh iftin g
tran sition b e lt between the more humid region of the sta te s to the east
and the drier region of the Great Plains to the West.
In periods of
years o f favorable moisture conditions the grass species adapted to the
northeastern sta te s do well in th is region,
for example, Kentucky blue-
grass during the period prior to 193^ was a prominent invader in eastern
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Nebraska pastures.
With, the onset o f drought years th is species has largely
disappeared from nonirrigated lands with the exception o f small patches in
protected areas*
In such unfavorable periods o f drought, attention is again
ca lled to the native species which have best withstood these reoccurring con­
d itio n s (IS ).
Prom another standpoint* the region i s in a m id-latitude which
i s the meeting ground of grasses adapted to cool seasons with those grasses
adapted to growth only during the warm seasons o f the year.
She mingling
o f these two groups of grasses such, as the species o f Agropyron* Elymus*
Stipa, and Eoelerla of northern extraction with those of Andropogon, Panicum.
and Bouteloua from the south, provided a maximum o f continuous growth in the
o rig in al p r a irie.
In order to plan for a well rounded program o f grass improvement i t
seemed desirable to conduct work on a number of the species which offer
promise o f adaptation to the varying conditions o f the region.
She occur­
rence and d istrib u tion of the native and introduced species adapted to the
Great Plains have been reviewed by Hoover (1 5 ).
Savage (19) reviews the
publications of the la s t 50 years on the subject o f natural revegetation
o f cu ltivated lands, and discusses the cultural methods applicable to the
reseeding o f the promising species in the Central and Southern Great P lains.
FIELD ENVIRONMENT
The region described i s characterized by a climate and by s o ils
e sse n tia lly those of grassland.
At Lincoln, Nebraska, records on precipi­
tation have been kept for 62 years and on temperature for 55 years by the
U niversity o f Nebraska and the TJ. S. Department o f Agriculture Weather
Bureau.
This short period o f elim atological record includes reoccurring
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periods o f drought o f varying in ten sity and duration.
The past ten years*
with the exception of 1931 and 193^, have "been drier years than the average
o f the period on record.
R ainfall was esp ecia lly low in the drought years
193^ and 1936* and the succeeding years have heen poor crop years not only
because o f low annual r a in fa ll, hut also because o f the depletion of reserve
moisture in the su b soils.
This deficiency in moisture i s indicated in Table
1, showing the accumulated d e f ic its o f moisture received during the la s t ten
years and during the previous five-year and three-year periods pertaining to
each o f the years since 1935*
The low amount of stored moisture in the subsoils during these years
has made transplanted seedlings dependent largely upon the r a in fa ll o f the
current year for establishment.
Table 2 presents the p recip itation by
months during the years 193& to 1939* as eonpared with the 62-year average
p recip itation by months.
The spring and summer months were drier than
normal in the years 1936, 1937, and 1939* In the year 1938, the f i r s t fiv e
months o f the year were above normal in p recip ita tio n .
The h i^ . temperatures during the summer months o f the dry years made
the moisture shortage more acute.
Table 3 presents a comparison of the
average monthly temperatures with the normals for the 55-y e a r period.
With but two exceptions, the months lay to September in clu sive had higher
than normal temperatures for the four years.
The cool weather o f May in
193S conserved the moisture which f e l l in the early months of the year to
make i t a good year for estab lish in g stands o f transplants.
The growing season a t Lincoln, Nebraska, as determined by the average
date ( i p r il 1?) for the la s t k illin g fr o st in the spring and the average
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fab le 1 . —A n n u a l precip itation a t Lincoln, Nebraska,
for the years 1930-1939 ancL the accumulated d e fic its
below the 62-year average of 27*09 inches, i /
Year
193©
1931
1932
1933
193*
1935
1936
1937
193S
1939
{Departure:
Annual . f Poffi
. Accumulated d e fic it s
.p r e c ip i-. 62-year {for the:for the previous
!• tation *• normal {period {5 years 53 years
: Inches : Inches : Inches : Inches : Inches
••• ••
•••••
20.7^
-6 .3 5
6.35
3M ©
•••••
+7.21
• *• e
Q,Qk
0 . 0H
• • • e•
26.19
-0 .9 0
26.50
©.63
e ♦• a•
•••••
-©.59
-9 .8 6
10 . %
17.23
10 . **9
11.35
12.23
12.19
5.SS
25*35
-1 .7 *
2h.60
- 13.00
26.09
25.23
W.09
32.96
32.92
19.36
-7 .7 3
22.^7
+1.26
19 . ^7
31.07
31.7©
2S.35
39.06
- 7.36
2S.57
19.73
13 .S 3
hJ Data obtained from the Annual Meteorological
Summaries for Lincoln, Nebraska, prepared by the U. S.
Department o f Agriculture Weather Bureau.
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Figures underscored are for periods of 'below normal p recip itation
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• I • *1 • *1 M « l • «
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figures underscored are for periods of above normal
Table 3«—Monthly and
aean temperatures for the years 1936-1939» with departures from the
10
11
date (October 1^) for the f i r s t k illin g fr o st in the f a l l , i s ISO days.
She early spring and la te f a l l growth of some of the grasses lengthens th is
period beyond the fro st-fr e e dates.
Bie m id-latitude p osition of the region
should be taken into account in interpreting dates o f transplanting grass
0
seedlings in the regions farther north or south.
She f ie ld s used for grass in vestigation s were on gently r o llin g lo e s s-
d
covered uplands and on terraces.
tEhese s o ils are c la s s ifie d in the same
general grouping of well-drained, dark and deep lo e s s ia l s o i l s ,
Biey are
s i l t loams and s i l t y clay loams in texture with mellow and fria b le surface
layers and su b so ils, allowing easy penetration o f roots and free movement
o f a ir and moisture.
She s o ils have a high water-holding power and fa ir ly
high in filtr a tio n capacity.
crop needs.
Although not high in lime they have enough fo r
In color these s o ils are dark greyish brown when dry and nearly
black when wet, the in ten sity of color depending on the amount of organic
material retained.
On parts o f the uplands the dark surface material has
been thinned and the organic material content has been considerably lessened
under cu ltiv a tio n .
gbeenhouse mtlrohmekt
She greenhouse used for th is study consisted of two adjoining 100- foot
sectio n s, each approximately 29 fe e t in width, joined together with one
headhouse including o ffic e and laboratory with pottin g benches and s o il
bins in the basement beneath.
One 29-fo o t glass-enclosed section , here­
a fte r referred to as the grass section , was used exclu sively for grass
breeding and seedling propagation work.
Some spaee was also available for
372031
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12
sp ecial studies requiring d ifferen t temperatures in section s devoted to the
improvement o f other crops, and in outside sash-covered coldframes.
Other
space was also available in these sections in la te spring for expansion of
the seedling propagation work,
fork with plants in the greenhouse reaches
i t s maximum during winter and spring months and d e fin ite planning i s re­
quired to secure a maximum u tiliz a tio n throughout these eolder seasons.
In these greenhouse section s the heat supply was furnished by steampipe radiators mounted on the exterior w a lls.
Minimum temperatures were
kept from f a llin g too low by supplemental fan-operated radiator units con­
tro lle d by thermostats,
luring the winter months, minimum temperatures
were held with l i t t l e daily fluctuation by these means.
Maximum tempera­
tures were d if f ic u lt to control during the warm seasons of the year and
required considerable attention to ven tila tio n even during the cold months,
luring a two-year period o f th is in vestigation beginning in the f a l l
o f 1936, records were kept o f the maximum, minimum, and mean daily air
temperatures in the grass section of the greenhouse,
The averages o f these
temperatures pertaining to the monthly germination te s ts are recorded in
fable
and are presented graphically for comparison with germination re­
su lts in Figure 12.
These data are for a twenty-day period follow ing the
planting o f the seed as th is number o f days best represented the period in
which the emergence o f most o f the seedlings took p lace.
I t was desired to have the grass section of Hie greenhouse operated
a t a moderate temperature considered optimum for the growth o f as many o f
the d ifferen t grasses as p o ssib le,
lurin g the f i r s t winter, minimum temper­
atures were held with l i t t l e daily fluctuations near 60° I .
Average maximum
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fal>le ^.—Average d a ily maximum, minimum, and mean
greenhouse teaperatureg pertaining to the monthly
germination periods*
■
______ Period________
:MaximumjMinimum: Mean
: P .° t g .° t P.°
Sept. 16 to Oct. % IS36
Oct. 21 to M o t. 9, 1936
M o t. 17 to Dec. 6 , 1936
Dec. 16 to Jan. 4 , 1937
Jan. 16 to Pet). 4 , 1937
Peh. 16 to March 7. 1937
March 13 to April 2, 1937
April 16 to May 5 , 1§37
May 16 to June 4, 1937
June 16 t©July 5. 1937
July 16 to Aug. 4, 1937
Aug. 15 to Sept. 3 , 1937
74
74
78
78
73
73
75
75
76
76
79
79
SI
81
f©
9©
106
106
iH
l lI
102
1©2
99
P53
62
62
59
59
,61
6l
62
62
6l6 l
6l
61
62
62
64
64
^9
69
70
70
Sept. 15 to Oct. 5, 1937
Oct. 16 to Mo t . 4, 1937
Mo t . 16 to Bee. 5, 1937
Bee. 16 to Jan. 4, 1938
Jan. 16 to Jet). 4, 1938
Peh. 15 to Mar. 6, 1938
Mar. 16 to Apr. 4, 1938
Apr. 16 to May 5, 1938
May 15 to Jane 4, 1938
June 16 to July 5, 1938
July 17 to Aug. 5, 1938
Aug. 16 to Sept. 4, 1938
Sept. 16 to Oet. 5, 1938
95
95
90
90
84
84
83
83
S2
82
82
82
94
94
98
98
i®5
i®5
99
99
109
109
102
102
102
102
56
5©
67
67
68
68
69
69
65
§5
68
68
70
70
JO
70
66
66
74
74
73
73
71
71
58
58
63
70
66
68
69
JO
71
76
S5
90
86
JO
75
78
jS
76
73
75
82
84
85
86
91
86
80
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temperatures were produced ranging from 73°
SO0 F,
Baese temperatures
were found sa tisfa cto ry for producing a good growth o f seedlings o f such
grasses as Poa oraten als. Aaronvron c r ista turn. and Bromus inenaia. and
o f clones o f Bromus inermis for seed production and breeding purposes,
During the summer months temperatures go beyond control and are unsuited
for the best growth of these grasses.
atures were raised s lig h tly ,
6S° to 86® F.
many seeds,
Daring the second winter the temper­
Hhey approached very c lo sely the temperatures
(20° to 30° 0 .) , considered optimum for the germination o f
September minimum temperatures were low in both years because
no heat was turned on during these periods.
During the summer o f 1938* the
maximum temperatures were somewhat sim ilar to those o f the f i r s t summer
except for the July period.
Minimum temperatures as recorded in the green­
house were higher in 1938 than in 1937*
During 1938* high minimum temper­
atures o f 70° or above were recorded for a period of fiv e months, consec­
u tiv e with the exception of May, during which the average minimum temper­
atures f e l l below JQ°,
Other temperature records were kept during the two months o f testin g
the e ffe c t o f temperature on the germination o f seed.
From October 21 to
November 9* 193^* a record comparable to that in the grass section was
taken in the coldframes out-of-doors, where a germination te s t was con­
ducted with the same seed lo t s as were being germinated in the grass sec­
tio n ,
®he average daily minimum temperature in the coldframes was 39°»
or 23° lower than in the greenhouse; the average d aily maximum temperature
was 73°» or 5° lower than in the greenhouse,
fh is made a difference o f
lU° in the average daily mean temperatures for the two germination con-
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d itio n s.
During February, 19371 a sim ilar te s t was conducted in a warmer
section of the greenhouse than that of the standard monthly germination
t e s t of that period.
This section o f the greenhouse had for the period an
average dally maximum o f 89° , which was 10° warmer than the grass section ,
an average daily minimum o f 69°#
8° higher temperature than the grass
section , and the average daily mean teaperature was. therefore. 9° warmer
than in the standard t e s t o f that month.
MATERIALS AND METHODS
Introduced and Native grasses
The grasses chosen for th is study were selected for th eir representa­
tion o f several taxonomic groups, as well as for their adaptation to d if­
feren t ecological conditions.
They were selected to include both native
and introduced species which offered promise for adaptation to the region.
Some r estr ictio n s in choice were necessary because o f the un availab ility
of seed su pp lies, p articu larly of some o f the important native grasses.
Since the seeds o f the native grasses were from large scale co llec tio n s
in one or more years, the most promising species from the standpoint of
seed production and commercial seed operations were represented.
The selectio n of species made from the grass trib es Hordeae, Festuceae.
and Fhalarideae. included a few native grasses and a l l o f the introduced
grasses considered in these t e s ts .
Agrorarron cristaturn (crested wheat-
g ra ss), an introduced grass, heads the l i s t o f the trib e Hordeae in the
tables presented on the germination of the grass seed.
ferred to as the wheatgrass group.
This group i s re­
The native grasses Agronyron sm ithii
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(western wheatgrass), Agropyron pauciflorum (slender wheatgrass), and Elymua
eanadensiB (Canada w ild -rye), were also in eluded from th is t r it e .
Of these
three sp ecies, a l l tu t the la s t may t e considered as cu ltivated grasses,
seed he tag available from commercial sources.
©le second taxonomic group­
ing referred to as the bromegrass group was made up en tire ly o f cultivated
grasses.
She introduced species Bromus inermis (bromegrass), D actylis
glome rata (orchard gra ss), and Boa pratensis (Kentucky blu egrass), repre­
sent festuceae.
Phalaris arundlnaeea (reed canary grass), i s included in
th is grouping although the morphological a f f in it ie s o f i t s trib e fhalarideae
are rather uncertain.
fhe remaining species f a l l in the category of native grasses which have
not as y et been widely brought under c u ltiv a tio n ,
fhey are l is t e d as the
third, fourth, and f i f t h groups in the tables on germination data.
The third
grouping i s referred to as the grama-buffalo grass group made up o f the three
grama grasses—Bouteloua eurtipendula ( sid e-oats grama), Bouteloua g r a c ilis
(blue grama), and Bouteloua hirsu ta (hairy grama), and a c lo se ly related
sp ecies, Buehloe daetyloides (buffalo grass), a l l representative of the
trib e Chlorldeae.
®ie fourth group i s the blue stem-switchgrass group, made
up o f Androuogon fureatus (big blue stem), Androuoaon sconarlua ( l i t t l e bluestem), and Sorghastrum nutans ( Indian gra ss), o f the tribe Andronogoneae.
and Panicum virgatum ( switchgrass) o f the tribe Paniceae.
This grouping
has beea made because o f sim ila r itie s in length of growing season of these
grasses and because o f the taxonomic relationships of the two trib es.
The
trib es Androoogoneae and Paniceae are the two principal trib es o f the grass
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subfamily Panicoideae (13).
The la s t group is referred to as the dropseed
group, composed of the two sp ecies, Sporobolus airoid es (a lk a li dropseed),
and Sporobolus cryptaadrus (sand dropseed),
These species belong to a
large undifferentiated subgroup within the tribe Agrostideae.
Further mor­
phological ch aracteristics of the species are more thoroughly described by
Hitchcock ( 13)*
C lassified on the b asis o f methods o f handling o f the grass seedlings,
the species lis t e d comprise only two main groups which w ill be referred to
resp ectively as the cool-temperature grasses and the warm-temperature grasses.
This c la s s ific a tio n is based primarily upon growth habits of these grasses.
The cool-temperature grasses may be defined as those grasses which
make their maximum growth during the cool f a l l and spring months.
The
grasses of the f i r s t two taxonomic groups lis t e d , the wheatgrass and brome­
grass groups, f a l l within th is category.
With these sp ecies, seed production
i s usually in itia te d during the long days of la te spring and early summer,
with seed maturity resu ltin g early in the summer season.
With adequate
moisture some of these species may extend th eir growth well into the summer
months, while others are dormant during the hot seasons follow ing seed
production.
These grasses are somewhat comparable in seasonal growth
habits to the cultivated small grains.
The th ree rem aining taxonomic groups o f g r a sse s in c lu d in g the s p e c ie s
o f B outeloua, Androuogon. and Sporobolus are warm-temperature g r a ss e s.
These grasses make their maximum growth during the warm months of the year
with growth almost e n tire ly confined to the fr o st-fr e e period.
Seed pro­
duction is variable throughout the season, some species maturing seed during
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18
mid-summer while others* lik e the bluestems, are long-season grasses requir­
ing the whole growing season to reach maturity.
These grasses are somewhat
comparable to the m illets* sorghums, and com , in th eir seasonal growth
h a b its.
Seed germination
A number of d if f ic u lt ie s are encountered in securing an adequate measure
o f the v ia b ility of some of the forage grass seeds.
With many o f these, the
earyopses are enclosed in attached glumes as normally handled.
The deter­
mination o f the presence of earyopses i s d i f f i c u lt , resu ltin g in the con­
fusion of purity determinations with v ia b ilit y .
The native-grass seeds fre­
quently present rather low purity due to the high percentage of attached
glumes and appendages, seed se ttin g varying in d ifferen t years.
Where the
earyopses are small, they may be advantageously removed for germination
studies but require careful scrutiny to determine mechanical injury to which
they may be subjected in cleaning for these special purposes.
d iffic u lty with the native species l i e s in seed dormancy.
The greatest
L ittle is known
about the germination requirements o f some of the native-grass seeds.
Blake ( 6) ran numerous germinations of the p rairie grass seeds and reported
best germinations daring the spring months.
To discover the problems involved in germination and seedling estab­
lishment for the propagation o f seedlings* a se r ie s o f 25 consecutive monthly
germinations were started in the greenhouse in September, 193&* usiug the
seed lo t s o f 17 species from the seed harvests of 1935 aud 193^*
Later the
seed o f the 1937 harvest was added to give three d iffe re n t ages of seed
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19
and the Med o f one other species was added to the test*
Seed supplies of
the introduced sp ecies were secured from commercial sources and o f the native
species from large scale seed harvests where th is was p o ssib le .
In securing
seed lo t s o f native grasses for germination studies the large co llec tio n s
have d is tin c t advantages for securing a uniform lo t o f seed* although i t
was not p ossib le to secure seed from such sources for a l l species in a l l
three years*
The seed lo ts were re cleaned and stored at room temperatures
in a laboratory room*
greenhouse sections*
This room was in the brisk headhouse adjoining the
Being on the north i t was a cool room during the
winter months* but during the summer months i t was subject to outside high
temperatures*
Representative normal earyopses from the recleaned seed lo t s were used
fo r the germination tests*
The seed was counted out by hand* considerable
care being taken to se le c t earyopses without regard to s iz e .
Where d i f f i ­
culty Was encountered due to attached glumes and appendages* the earyopses
were rubbed free o f the glumes in recleaning the seed lot*
3h is was done
with Androuogon furcatus. jgorghastrum nutans, the sp ecies o f Bouteloua.
and with Buehloe daetyloides.
The long narrow earyopses o f Andronogon
scop arias were not su ccessfu lly removed from the glumes without consider­
able cracking*
This seed was counted on a g la ss p la te over diffused lig h t
or pinched lig h tly with forceps to determine the presence of the earyopses*
Using these methods, no d iffic u lty was experienced in determining the
presence o f earyopses o f the grasses in the trib es Hordeae, Jestuceae, and
Phalarideae. in which the glumes are retained.
With the m ille t-lik e seeds
of Pan1cum Viraatum. the u n fille d glumes were removed with an a ir b last
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20
in recleanlng the seed lo t s .
!Ehe dropseeds were e a sily cleaned free o f the
glumes and except for the smallness of the seed* were e a sily counted.
R eplicates o f the seed lo t s o f toe cool-temperature grasses were o f
100 seeds each.
Lack o f uniformity in seed size and v ia b ility and low ger­
mination o f some species made 200 seeds a more desirable number for the
native species in toe warm-temperature group.
Only 100 seeds removed from
the burs were used* however, for the germination t e s t s o f the seed of
Buchloe dactvlolAes.
USie seed was planted in tr ip lic a te on toe surface
o f well-packed* s te r ilis e d s o i l , in bands o f asphalt f e l t approximately
three and three-fourths indies square, twenty-four to a s o il f l a t .
Bie
seed was covered to a depth of about one-fourth inch by the application
o f a measured quantity o f fin e sand,
fhe tr ip lic a tio n s were planted in
d ifferen t f la t s and in d ifferen t p osition s within toe f l a t s .
She seed
was planted as nearly as possib le on toe fifte e n th o f each month.
Hence,
the germination r e su lts represented as occurring in any one month were
fo r seed germinations which usually occurred in toe la tte r h a lf of toe
calendar month.
Bhe f i r s t count of the emerged seedlings was usually taken about
the sixth day a fte r planting, and the count repeated a t Increasing in ter­
v a ls from three to ten days (F ig. 1 ).
She rapidity of germination could
thus be determined and the to ta l number o f emerged seedlings could be as­
certained even though, lo sse s occurred.
Bead seedlings were counted and
removed, toe number o f seedlings l e f t being recorded in order toat an in­
crease in germination could be determined a t the next counting.
She to ta l
germination o f the seed as measured by toe emergence o f toe seedlings and
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iPig. 1. —She determination o f grass seedling emergence and
establishment in the greenhouse s o il germination stu d ies.
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th eir fin a l establishment were recorded at the end o f a 30-day period with
the f i f t h or sixth count.
Data reported for every t r ia l are averages o f
the three replications* except in a very few eases where one of the rep li­
cations was destroyed.
Checks on germinations run on b lo tte r s in germinar-
tors with controlled alternate temperature (20° to 30° C.) were run only
in duplicate.
By planting additional se ts of tr ip lic a tio n s o f the same seed lo ts
under d ifferen t conditions la any one month, te s ts were conducted on the
e ffe c ts of s o il s te r iliz a tio n , s o il f e r t i l i t y , and o f d ifferen t tempera<tures on germination as compared with the standard monthly t e s t .
With the
exception o f the la t te r te s ts on temperature d ifferen ces, these te s ts were
conducted in the grass section of the greenhouse a t the recorded temperature
Soil f l a t s and Paper Bands
Cypress s o il f la t s approximately 22* x 15* x *+n by inside measurement
are used for the growing of grass seed lin gs.
They have an advantage over
s o il beds in th eir movability and over clay pots in their u tiliz a tio n o f
space, factors not to be overlooked in maintaining uniformity o f growth
and e ffic ie n c y of operations.
to be described.
A standard siz e i s desirable for the purposes
Seedlings are usually grown in a small amount o f s o il
separated by bands of a sp h a lt-fe lt paper in the s o il fla ts*
A sp h alt-felt roofing paper (not tarred paper) i s a standard product
sold in th r ity -s ix inch r o lls containing 4 squares or H32 square fe e t.
The 12-pound weight per square has been found most sa tisfa c to ry , but the
13-pound and 10-pound weights have also been used.
A machine has been
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devised to cat these r o lls Into foar-inch s tr ip s , and into any length for
making plant hands of d ifferen t siz e s (Pig* 2)*
are apron r o lle r s from a grain hinder,
hinder sick le sections*
the r o lle r s of the machine
the cutters are sharpened grain
Circles of sheet metal between the strip s as they
are being cut, prevent wrapping of the separate str ip s over one another.
After the r o ll has been cat lengthwise the str ip s are p alled hack across
a wooden platform placed over the cutter bar.
A narrow hoard marks the
length to which the str ip s are p alled before they are cut crosswise with
a r o llin g cutter operating in a groove between two p ieces o f strap iron.
Asphalt f e l t cats best when i t i s cold.
I t fold s b est when i t i s warm.
$he f e l t str ip s o f a desired length are folded around a piece of
metal o f the correct width and then inserted, without stap lin g, into a
s o il f l a t containing a set of metal forms ( f i g . 3)•
use o f such a
se t o f forms to make up f la t s for growing individual seedlings was f i r s t
suggested by Dr. P. C. Herbert o f the Soil Conservation Service, U, S.
Department of Agriculture, Santa Paula, C alifornia.
She se t shown in
pigare 3 contains bands which are approximately 1- 3/k x 1- 3A x ^ inches
forming ei^ht rows of 12 bands each, or 96 per f l a t ,
fh is small size i s
the standard siz e used, providing enough seedlings to grow two selection s
of MO p la n ts, or four selectio n s o f 20 plan ts each per row, with opportunity
for discarding a few p lan ts.
Other sets have been constructed with bands
approximately 2 x 2 x 4 inches, 77 to a f l a t , and 2- 1/2 x 2- 1/2 x ^ inches,
to a f l a t .
By omitting one-half o f the dividers used in the small s e t,
a set o f forms pictured in Pigare ^ is used for making up the f la t s for the
germination of seed selectio n s and for germination studies (P ig. 1 ).
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2^
2?ig, 2. —A machine for cutting r o lls of a sp h a lt-fe lt paper into
four-inch str ip s and then into any length of plant hand
for growing grass seedlings. The wooden platform is
placed between the r o lle r s for making the cross cut.
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J ig . 3 . —Apparatus for forming a sp h a lt-fe lt paper hands to he
used in s o il f la t s for growing grass seedlings* These hands
shaped around a f l a t pieee o f metal, are inserted without
stap lin g. The metal forms are removed a fte r securing a uni­
form packing o f the s o il.
Fig* ^*— The m etal forms used to make up f l a t s o f la r g e hands
o f s t e r i l i z e d s o i l fo r g e m in a tio n and esta b lish m en t o f
seed lin g s*
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In constructing the metal forms the dividers are f i r s t cut to siz e for
length and for width with tin snips.
After marking o ff the metal, the
meshing o f the two lengths o f dividers is made p ossib le by sawing s l i t s in
the metal with a hacksaw.
The correct width o f s l i t i s obtained by using
double hacksaw blades, the one reversed in direction to the other.
She
cut on each length o f divider i s made on a l l the dividers at once by bolt­
ing them together.
S oil f la t s are made up by f i r s t f i l l i n g the metal forms with bands
and then f i l l i n g the f l a t with the proper s o il mixture.
A uniform packing
o f the s o il can be obtained by le v e lin g the loose s o il with the hands, and
by dropping the s o il f l a t a few inches upon
can then be added to again f i l l
a so lid flo o r .
Additional s o il
the f l a t le v e l, after which the metal forms
are removed and used again.
Soil Mixtures and S te r iliz a tio n
Hie s o ils used in the greenhouse work were largely s i l t loams in tex­
ture secured from along roadsides and edges of cultivated f ie ld s .
Hie s o il
was stored in s o il bins in the greenhouse a fter being thoroughly pulverized
by running i t through an ensilage cutter.
Where the s o il i s returned to
the f ie ld each year in the propagation o f seedlings i t i s necessary to use
a new supply, and i t i s d if f ic u lt to secure adequately f e r t i le s o ils com­
parable to the potting s o ils used in commercial greenhouse p ractice.
add f e r t i l i t y , w ell-rotted manure has been used e ffe c tiv e ly .
To
Manure from
large p ile s of aged, moist cow manure may be prepared for storage in green­
house bins by running i t through an ensilage cutter or threshing machine
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27
cylinder.
A haminermill has been used e ffe c tiv e ly for producing a fin e ly
ground product.
Soil mixtures consistin g o f varying proportions o f s o i l ,
sand, and manure were used fo r d ifferen t purposes.
For the germination stu d ies, s o il mixtures were s te r iliz e d in a large
autoclave a t 15 pounds o f steam pressure for a period of three hoars,
Waks-
man ( 23) sta te s that a s o il may he s te r iliz e d completely by subjecting i t
to steam pressure of 15 pounds for two hours, or for one hour on seven con­
secutive days in flowing steam.
Since the amounts o f s o il handled were
usually quite large and were heated only once, i t i s lik e ly that only a
p a r tia l s te r iliz a tio n was ever brought about.
The staadard s o il mixture for the germination studies consisted of fiv e
parts of s o il to one part o f sand and one part o f the screened, w ell-rotted
manure.
Both u n ste riliz ed and s te r iliz e d s o ils with and without manure were
tr ie d for the germination of seed.
For seed germination and early growth o f
ing
seedlings
the standard s o il mixture for germination was used.
good structure and moisture holding capacity to the s o i l .
for f i e l d transplant­
She manure gives a
She sand f a c i l i ­
ta tes the removal o f the seedling from th is mixture to the small bands as
sin gle p la n ts.
S oil mixtures for growing the separate seedlings varied.
One or two parts of manure to fiv e parts of s o il with or without sand have
been used in the te s ts of seedling growth in conparison with chemical fe r ­
tiliz e r *
These s o il mixtures were not s te r iliz e d .
Spotting and Transplanting
Seedling plants for transplanting to the
by germinating the seed in s te r iliz e d s o il in
f ie ld are
usually obtained
f la t s of the large bands as
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28
used in the germination studies (Pigs* 1 and 4 ).
When the seedlings have
obtained a su itab le age, they are transferred as sin g le plants to f la t s of
the small bands.
Ihese f la t s are f i l l e d with s o il o f the proper mixture
and moisture content.
She large band o f seedlings is removed from the ger­
mination f l a t and placed on i t s side (P ig. 5)*
A seedling i s removed by
breaking down the moist s o il with the fingers and gently l i f t i n g the top
o f the seedling.
I t i s then se t over into the f l a t o f small bands and
firmed into p o sitio n by two movements o f the wooden dibble used to make
the hole for the entrance of the roots.
Shis procedure i s designated as
"spotting8 in contrast to the la te r procedure of "transplanting" the seed­
lin g s to the f ie ld .
Plants are grown for periods o f from two to four months in the green­
house and coldframes.
She length o f the period depends upon the rapidity
o f growth o f the grass, the time o f year then started , and the weather con­
d itio n s in the transplanting season.
Pigare 6 shows f la t s o f seedlings o f
Agrouvron c r ista turn and Bromus inermis at an age o f two and one-half months
from the date of seeding,
seed was planted.
trated.
tfihey were spotted two to three weeks after the
A method o f transplanting to the f i e l d i s also illu s ­
A core of d ir t is removed with a core remover, designated commer­
c ia lly as an English bulb planting to o l,
(Che seedlings in bands are d is­
tributed along a row of such holes in the f ie ld and are set into place by
firming moist s o il around them with the hands*
I f the surface s o il i s
very dry, the bands may be l e f t on the seedlings in order to retain a
maximum of moisture around the roots.
She plants may be retained in
good condition for several weeks u n til well-rooted into the s o i l .
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Ihe
:______________________________________
J
P ig. 5. —Spotting the sin gle seedlings from the s te r iliz e d
s o il of the germination f l a t to the small plant hands.
(Pig. 6 .—She method of growing individual grass seedlings in the
greenhouse for transplanting. An English "bulb-planting tool
i s used in the f ie ld for making holes into which the plants
are se t.
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common p ractice has been to remove the bands, retaining the moist s o il around
the roots and placing i t in contact with moist s o il i f p o ssib le .
I t has n o t been found f e a s ib le to u se water in tr a n sp la n tin g to non­
ir r ig a te d lan d s because o f the pu ddling e f f e c t on the s o i l which lim it s
r o o t growth to the sm all area surrounding th e p la n t.
3he s u c c e s sfu l trans­
p la n tin g o f s e e d lin g s i s th er e fo re la r g e ly dependent on the fa v o ra b le mois­
tu re co n d itio n s o f the whole s o i l mass.
She topography and in a c c e s s ib ili t y
to w ater made ir r ig a t io n p r a c tic e s lim ite d to sm all a r e a s.
Since the g ra ss
problems are th ose c h ie f ly concerned w ith ad ap tation to n o n ir r ig a te d la n d s,
the growing o f g r a sse s w ithout supplem ental water i s n o t considered an undue
handicap.
EXPERIMENTAL RESULTS
term ination Methods
E ffects of s o il s te r iliz a tio n . —In a germination t r ia l conducted in
August, 1936, i t became evident that in order to obtain r elia b le r esu lts
in the s o il germination studies with grass seed, the factor o f seedling
d iseases would have to be taken into consideration.
Certain ir r e g u la r itie s
developed in the emergence o f seedlings in the rep lica tio n s, and lo sse s of
seedlings a fter emergence with some species were so great that r elia b le
counts could not be obtained.
These lo sse s appeared to be due to types o f
"damping off" which resulted from the action of organisms eith er prior to
emergence or follow ing the emergence of the seedlings above the s o i l .
e ffe c ts have been reported fo r other plants (l^» 16) .
These
Beginning the follow ­
ing month, a se r ie s o f te s ts o f the seed lo t s of the 1935-harvested seed
were run in both s te r iliz e d and u n sterilized s o ils .
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She germination te s t in September, 1936, was se t up to determine the
response of germination and seedling establishment in a steam -sterilized
s o il mixture as compared to the response in steam -sterilized sand and in an
u n sterilized s o il mixture (Table 5 ) ,
A ll o f the 15 species gave increases
in germination as determined by the emergence of the seedlings in the ster­
iliz e d , as compared to the u n sterilized s o il mixture.
Two species gave
efu a lly as good germination in s te r iliz e d sand as in the s te r iliz e d s o i l .
For the remaining sp ecies, the number of seedlings produced in the ster­
iliz e d sand was usually eith er intermediate between the numbers in the
s o il mixtures or below those of the u n sterilized s o il mixture.
in the s te r iliz e d s o il made much more growth.
Seedlings
Seedling lo s s by disease
was greatest in the u n sterilized s o il and lo sse s also occurred in the sand
because of a deficiency o f available nutrients for making a good growth.
Seedlings grown in the sand were very poor for spotting.
Using the s te r iliz e d s o il mixture as the standard medium in the follow ­
ing monthly t e s t s , fiv e check germination te s ts of the same seed lo ts in
u n ste riliz ed s o il mixtures were conducted during the f i r s t year o f the
te sts.
Average increases in germination and seedling establishment of
plantings in s te r iliz e d s o il over those in u n sterilized s o il are reported
for 16 species in Table 6.
She data of the table indicates two main e ffe c ts
o f s o il s te r iliz a tio n —an increase in germination as determined by the
emergence of seed lin gs, and an increase in the survival of the seedlings
a fter emergence.
Average seedling emergence above the s o il was greater in the germina­
tion te s ts in the s te r iliz e d than in the u n ste riliz ed s o i l mixtures, for
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32
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3*
most of the sp ecies.
She f i r s t two taxonomic groups, comprising the cool-
temperattire grasses, showed le s s marked increases than did the three groups
o f warm-temperature grasses.
Of the cool-temperature grasses the average
increase was greatest for Agronyron sm ith ii.
She other germinations tended
to flu ctu ate "between the several tr ia ls in showing the advantages o f s o il
s te r iliz a tio n .
Of the warm-temperature grasses, a l l of the te s ts in ster­
iliz e d s o il with the exception of those o f Panicum virgatum and Sorghastrum
nutans, showed marked increases of emergence in the separate monthly t r ia ls .
With the cool-temperature grasses, differences o f emergence as great
as 15 per cent for 4 . sm ith ii, 16 per cent for Bromus tnermis, 11 per cent
fo r D actylis glomerata. and 20 per cent for Phalarls arundlnacea occurred
in some one of the t r ia ls in favor o f the s te r iliz e d s o i l .
In some one of
the fiv e t r ia ls with the groups of warm-temperature grasses, d ifferences as
great as the follow ing occurred:
6l per cent for Bouteloua curtipendula.
58 per cent for ]3. g r a c ilis , 52 per cent for Buehloe d actyloid es. Hg per
cent for Androoogon furcatus, IS per cent for 4 . seoparlus. and 3^ per cent
for Sporoholus a iro id es, in favor of the s te r iliz a tio n .
33ie second e ffe c t o f s o il ste r iliz a tio n was that o f favoring the es­
tablishment of the seedlings.
fable 6 shows percentage increases of seedf
lin g establishment in the s te r iliz e d s o il fo r Agrouyron cristatum. A. sm ith ii,
Bouteloua g r a c ilis , and Sporobolus airoides much larger than the percentage
increases due to emergence of the seed lin gs.
Ehis i s due to lo sse s in the
u n ste riliz ed s o il from seedling diseases a fter emergence.
occurred in the s te r iliz e d s o i l .
Some lo sse s also
fh is was p articu larly true for Bouteloua
curtipandula, where 11 out of 6^ per cent o f the seedlings were lo s t in the
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35
s te r iliz e d s o il as compared to 7 out of 17 per ceat for the u n ste riliz ed
s o il; aad with Bouteloua C T acilis. where 7 our of 65 per ceat were lo s t in
s te r iliz e d soil' as compared with 26 out of 50 per cent in the u n sterilized
soil*
A third e ffe e t o f s o il s te r iliz a tio n was the increased growth and vigor
o f the seed lin gs.
Both tops and roots grew more rapidly, and the leaves
developed a darker green color in the s te r iliz e d than in the u n sterilized
s o il.
Shis e ffe c t i s due to the increased a v a ila b ility o f plant nutrient
m aterials produced by the heating of the s o i l , and to the increased b acterial
action in the s o il follow ing s te r iliz a tio n (23* 2^, 25).
Although, the s o il
mixtures for these studies were s te r iliz e d a t high temperatures, only p a r tia l
s te r iliz a tio n of the s o il was effected because o f the qu an tities o f s o il
involved and since the opportunities for re-inoculation in the greenhouse
were so great.
Agar culture-plate te s ts o f the s o il immediately after i t s
removal from the s t e r iliz e r showed considerable contamination by the bac­
te r ia remaining in the s o il, but no fungi developed,
She e ffe c ts of p a r tia l s te r iliz a tio n o f s o il upon s o il b io lo g ica l
a c t iv it ie s have been summarized by Waksman and Starkey (2h, 25), and by
Waksman (2 3 ).
Biey have shown experimentally ■toe reduction in numbers of
fungi and bacteria by heat treatment o f s o i l , followed by their rapid in­
creases.
She b acterial flo r a i s sim plified by the death and extinction o f
some o f the v a r ie tie s in the s o il while others are subsequently increased.
Protozoa and certain fungi are frequently e n tirely elim inated.
S te r ili­
zation by heat r e su lts in the destruction o f the n itr ify in g bacteria, which
are slow to re-enter the s o il ( 23» 25) .
She heating o f the s o il increases
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the s o lu b ility of both mineral and organic m aterials which become available
for p la n ts, the increase being greater in s o ils rich in organic matter, than
in mineral s o ils (2 3 ),
The increase in soluble matter and the changes in
the m icrobiological population resu lt in an increase in the production and
accumulation o f ammonia during the period follow ing s te r iliz a tio n , u n til
now eq u ilib ria are established in the s o il and n itr ific a tio n i s resumed
(23, 23)*
Heat also e ffe c ts a floccu lation of s o il c o llo id s, thus changing
the physical condition o f the s o il ( 23)•
These changes account for the
b e n e ficia l e ffe c t on plant growth.
These phenomena make the described methods o f securing i n i t i a l seed­
lin g establishment in s te r iliz e d s o il with spotting to separate plant bands,
very desirable methods to be employed in the propagation of grass seedlings.
The seed germination and seedling establishment are increased, the seedlings
make a rapid and vigorous growth as a resu lt of the increased a v a ila b ility
o f nutrient m aterials, and the seedlings are removed before such time as
any unfavorable e ffe c ts due to competition of the seedlings or poor physical
s o i l structure r e su lt.
Removed to u n sterilized s o il they continue growth
with only a short interruption while becoming re-estab lish ed .
Some d iffic u lty was encountered because of the growth and fr u itin g of
saprophytic organisms which found the s te r iliz e d s o il an ex cellen t medium
for growth.
Several ordinary molds occurred.
The most prevalent organism
covered portions of the s o il surface with a pink or pale-orange fungus growth
which in the course of i t s development offered tenporary obstruction to the
l / This organism was id e n tifie d as a Ryronema by Dr. F. J. Seaver, of the
Hew York Botanical Garden. I t i s o f frequent occurrence on s te r iliz e d
s o il.
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emergence of seedlings in a few instances.
I t was usually confined to the
shaded edges o f the containers, or occurred when the germination f la t s were
exposed to low l i ^ i t in te n s itie s in the greenhouse.
I t was p a r tia lly con­
tro lle d hy planting and covering the grass seed with sand immediately a fte r
s te r iliz a tio n of the s o il mixture, and by allowing the surface o f the sand
to dry a fter watering.
The germination o f the seed was thus allowed to pro­
ceed without favoring the growth o f the organism hy providing a continuously
moist medium.
With these precautions, no detrimental e ffe c ts on the germina­
tion or the emergence and establishment of the seedlings were observed,
I f f e c t s o f kind of s o i l , —The hi^ier germination of seed in the ster­
iliz e d s o il mixture as compared with germination in the u n sterilized mixture
led to inquiry into the e ffe c ts of the manure in the mixture.
Attempts were
made to determine whether the inclusion of the manure in the u n sterilized
and s te r iliz e d mixtures affected germination and growth of seed lin gs.
Tests o f germination in u n sterilized s o il mixtures with and without
manure gave sim ilarly poor resu lts in the emergence and establishment of
seed lin gs,
from these t e s ts , i t appeared that the unfavorable factors were
in the s o il i t s e l f rather than in the manure.
Germination was greater in
s te r iliz e d mixtures with or without manure than in u n ste riliz ed mixtures.
The e ffe c ts o f the degree o f f e r t i l i t y on the emergence and estab lish ­
ment o f seedlings in the f e r t ile s te r iliz e d mixtures w e re not so e a sily de­
termined.
A te s t of germination o f the 1935 seed lo t s in s te r iliz e d s o ils
with and without manure was run in each of three months— In December, 193&»
and in January and March, 1937.
most o f the sp ecies.
D ifferences in emergence were small with
There was a tendency for the more f e r t ile mixtures
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to give the higher germinations in the months when other factors were also
favorable for a higjh percentage of germination.
Although these resu lts
were not conclusive, i t appears from these tendencies and from the increases
obtained in the s te r iliz e d s o il mixture over the s te r iliz e d sand (fab le 5 ),
that the degree o f f e r t i l i t y may operate in conjunction with other factors
in determining the vigor and rapidity with which the seedlings o f smallseeded grasses emerge from the s o il and become established.
E ffects o f d ifferen t temperatures.—Although i t appeared desirable
to continue the main germination te s ts in the grass section o f the green­
house with temperatures most nearly optimum for a l l the sp ecies, the ques­
tion arose as to what extent the germination o f the seed o f certain species
might be benefited by d ifferen t temperature conditions,
f e s ts of germinafc ion
under d ifferen t temperatures were conducted in the coldframes in comparison
with those in the grass section o f the greenhouse during October,
fhe var­
ia tio n in temperatures was 1*+° F. lower in average d aily mean temperatures
for the coldframe te s t than for the
standard monthly t e s t .
Germination
te s t s with higher temperatures were conducted in the warm section in com­
parison with t e s ts in the grass section of the greenhouse during February,
fhe variation in temperatures was 9° F. warmer in average d a ily mean tem­
peratures for the te s t than for the
standard monthly t e s t .
R esults of
these te s ts are given in fab les 7 aud S, and certain aspects o f temperature
rela tio n s to germination are discussed in the paragraphs dealing with the
monthly s o il germination te s ts o f the several sp ecies.
In the f i r s t of these te s ts (fab le 7) the seed of the eool-tenperature
grasses gave smaller differences in germination under the two tesperature
conditions than did the seed of the warm-temperature grasses.
Bromus
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39
Table
o f d ifferen t temperatures i / on the seed germination and
seedling establishment o f sixteen forage grasses. Seed from the 1935 harv e st planted in s te r iliz e d s o il in the greenhouse and in the cold frames*
October 20, 1936*
e
!
Goldframes
Greenhouse
:
;
s
:
:
Jiaergemee JEstablishment {Emergence sEstablishment
t
!
:
s
i
Species
Agropyron c r ista turn
Agropyron sm ithii
Agropyron pauciflorum
Bromus inermis
D actylis glomerata
fh a la r is arundinacea
Bouteloua curtipendula
Bouteloua g r a c ilis
Bouteloua hirsu ta
Buchloe dactyloides
Andropogon furcatus
Andropogon scoparlus
Sor#astm m nutans
Panicum ▼irgatum
Sporobolus airold es
Sporobolus cryptandrus
9$
912©
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57
6o
24
51
H
s
ks
2253
331
H§
3k
S3
12
85
53
%
9625
5
8597
51
15
32
5k
1k38
1305
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6
12
2253
321
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5
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21
90
65
5
s5
56
47
2
12
2
13
H
12
1+2
21
209
i / See Table 4 for the record o f temperatures in t h e g r e e n h o u s e .
R ep ro d u ced with p erm ission o f the copyright ow ner. Further reproduction prohibited w ithout p erm ission.
MQ
inerm is, D actylis glomerata, and. Phalaris arundinaeea gave equally as good
r e su lts in the two temperature conditions.
Agropyron sm ithii and Agropyron
pauciflorum
gave soaeidiat b etter resu lts in the medium temperatures o f the
greenhouse,
fhe Andropogon spp., Bouteloua spp. and Buchloe dactyloldes
gave marked increases in germination in the medium temperatures as compared
to those o f the coldframes where low minimum temperatures occurred.
On the
other hand, Sorghastrum nutans and Sporobolus airoides gave increased ger­
mination due to the c h illin g o f the seed, a fa c t which d isclosed the con­
d itio n s favorable for breaking the seed dormancy in these sp ecies.
In comparing medium with warm temperatures for germination, seed from
two seasons' harvests was included ( Table S ).
With the seed o f the eool-
teuperature grasses which might have been expected to germinate best in
the medium temperature, the d ifferences were small in a l l cases, the two
ages of seed tending to give differences in the opposite d irectio n s.
It
appears that both temperature conditions were within a su itab le range.
However, a restr icte d germination o f most of the cool-temperature grasses
was la te r encountered in the hot months o f summer.
Of the warm-teuperature grasses, Bouteloua g r a c ilis and Andropogon
furcatus gave moderate increases with one o f the two seed l o t s , while
Bouteloua eurtipendula, Buchloe dactyloldes, Andropogon scoparius, and
Sporobolus airoides gave increased germination with both ages o f seed in
the warm section of the greenhouse,
fhe increases with one or more seed
lo t s of these species indicate that somewhat higher germinations mi^it
have been obtained in the winter months i f the germination te s ts had been
conducted in a warm section o f the greenhouse,
fh is conclusion i s not
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rH|
warranted as a generalization for a l l of the warm-temperature grasses since
other factors also appear to "be in operation.
Where the warm temperatures
fa ile d to give increases for "both seed lots* the age and previous storage
conditions of the seed appear to he more important fa cto rs.
In order to better understand the e ffe c ts of the factors involved, an
evaluation o f additional information cn the germination behavior of one or
several seed lo t s is necessary.
Shis has been secured with the series o f
monthly germinations of the IS sp ecies.
In these te s ts a favorable seed
germination of several o f the warm-temperature grasses in September, when
the temperatures in the greenhouse were low, indicates the operation of
other lim itin g factors than a low temperature during the winter.
On the
other hand, the high maximum and minimum temperatures of the summer months
were also lim itin g factors to seed germination of the warm-temperatore
grasses.
Ihe operation of more than one factor i s shown by the trends in
germination, discussed in connection with each sp ecies.
Germination Studies with Eighteen Species
In order to approach the objective of securing high percentages o f ger­
mination and seedling establishment, information on the occurrence of dormancy
o f seed as well as information on the e ffe c ts of the environmental factors
including d isease, must be known.
She se rie s o f monthly germination te s ts
was undertaken to determine the germination and seedling establishment be­
havior o f d ifferen t ages o f seed -under the e x istin g greenhouse conditions.
Prom these r e s u lts , the b est time and manner of germinating the seed was to
be determined in relation to the establishment of seedlings in the greenhouse
and la te r in the f ie ld .
Hie s o il germination history o f the seed lo t s pre­
sents th is information and certain p o s s ib ilit ie s for modifying the ex istin g
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conditions to obtain the desired ob jectives.
She numerical data secured in
the 25 consecutive monthly germination te s t s in s te r iliz e d s o i l is presented
in fables 9. 10, and 11, for a l l o f the seed lo t s ,
These data are supple­
mented with the data previously presented on the e ffe c ts o f s o il sterilizartion and f e r t i l i t y , and on the e ffe c ts of temperature, conducted with the
same lo ts o f 1935 and. 1936 seed.
fhe grouping of the species Into groups of cool-temperature and warmtemperature grasses i s one made primarily on growth h ab its, as in it ia lly
defined.
Since the seeds of the grasses within these groups gave sim ilar
reactions in germination, th is grouping also o ffers p o s s ib ilit ie s for gen­
era lization on germination behavior.
The pertinent information concerning
the seed lo ts and their reaction to season, temperature, and other fa cto rs,
i s discussed in th is grouping, and in the same order as the species are
l is t e d in the ta b les.
Figures 13 to 27 in clu siv e, present the trends of
germination o f 15 species in relation to season.
Ihere data for more than
one seed lo t o f a species are given in fab les 9; 10, and 11, the data used
in the graphs are those o f the f i r s t seed lo t lis t e d .
The r esu lts of check
germinations o f the same seed lo t s in u n sterilized s o il t e s t s , and in b lo tte r
te s ts under standard temperatures (20° - 30° C.) i s also presented on the
graphs.
Seed germination of the cool-temperature grasses. —fhe 1935 and 193^
seed lo t s (fa b les 9 and 10), and the second l o t o f 1937 seed o f Agropyron
cristaturn (fable 11) were secured from the Experimental Substation at
Dickinson, North Dakota,
fhe f i r s t lo t o f 1937 seed l is t e d in fable 11
was grown at Lincoln, Nebraska, from a planting made in 193&, the original
R ep ro d u ced with p erm ission o f the copyright ow ner. Further reproduction prohibited w ithout p erm ission.
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
fable 10.—.Germination, o f 193& seed o f seventeen forage grasses during each o f 25 consecutive months
follow ing harvest. The seed lo t s were tested in s te r iliz e d s o il in the greenhouse.
:
S p ecies
••
••
1936
ee
1937
1 S e n t.! Oct. M o v . { D ec. { Jan. i P e b .! Mar. : A »r. 1 May i June! Julys Aug.
P. c t . P .c t, P .c t . P . c t . P .c t . P .c t , P .c t . P . c t . P .c t , P .c t . P .c t . P . c t .
Agropyron cristatum
Agropyron sm ith ii
Agropyron pauciflorum
84
81
94
85
91
73
84
65
91
70
89
82
92
77
91
81
92
78
71
75
7^>
78
82
89
Bromua inerm is
D a c ty lis glomerata
Foa p ratem sis
P h a la r is arundinacea
80
83
•*
83
91
91
92
91
84
71
93
91
83
85
77
84
82
77
88
86
49
75
89
87
80
68
67
76
47
61
75
83
85
91
75
97
88
•
*•
13
38
71
21
53
23
83
52
80
77
94
92
83
86
75
92
77
76
50
79
37
••
3
2
4
35
7
33
9
4e
43
16
49
27
58
14
55
26
42
44
••
45
4o
18
33
48
56
47
45
4l
13
27
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18
55
0
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0
11
12
0
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1
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1
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1
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7
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18
lg
29
29
8
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12
5
20
24
2
29
12
15
34
9
13
7
12
36
63
11
81
28
86
60
73
56
63
21
78
28
Bouteloma curtipendula
B outeloua g r a c il is
lo u t e le u a g r a c il is
B outeloua h ir s u ta
Buchloe d a cty lo id es
Buchloe d a cty lo id es
Andropogon fu rcatu s
Andropogon fu rcatu s
Andropogon seoparius
S o r i a s tram nutans
Panicum virgatum
Sporobolus a ir o id e s
Sporobolus cryptaadrus
*
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»&&&
source being the Northern Great Plains F ield Station at Mandan, North Dakota.
These seed lo t s gave an excellen t germination.
Bie te s ts on the e ffe c t o f
s o il s te r iliz a tio n showed slig h t increases in emergence and a considerable
h i^ ier establishment and b etter vigor of seedlings In s te r iliz e d than in un­
s te r iliz e d s o i l .
Loss o f seedlings due to disease was greatest with th is
species as compared with the other cool-temperature grasses.
The seed lo t s
gave an ex cellen t germination in s te r iliz e d s o il a t a l l times o f the year
except when temperatures were too high (F ig. 12 and 1^).
in June o f 1937*
This occurred
During the summer o f 193® the germinations were lowered
during several months, due to continued high minimum and high maximum tem­
peratures.
The 1935 seed, lo s t v ia b ility rapidly during 1938,
1935
o f Agronvron sm lthii was obtained from a bulk seed lo t
harvested from native grasslands in the v ic in ity of Rosebud, South Dakota
(Table 9)> the 193^ seed was a small lo t of seed from native grasslands
in western Nebraska (Table 10); the 1937 seed was harvested from a se­
le c tio n block o f transplanted plan ts grown from the South Dakota seed
(Table 11).
The average increase in germination as a resu lt of s o il ster­
iliz a tio n was greatest with th is species in comparison with others o f the
cool-temperature group.
Some lo sse s o f seedlings due to disease a fter
emergence occurred but these were not as great as with A. cristatum.
Seed­
lin g s o f A* sm lthii were more uniform in emergence and seedling growth in
the ste r iliz e d than in the u n sterilized s o i l .
In the monthly te s ts the
seed lo t s gave a high germination in a l l months except in the hot months
o f summer (F igs. 12 and 15).
There was a tendency towards lowered germina­
tion for th is seed during the winter.
In the te s ts under d ifferen t tempera­
tures the germination of 4 . sm lthii was lowered considerably more in the
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cold-temperature te s t than was the germination o f 4 . cristaturn,
This i s
in terestin g when a comparison of the regional adaptation of the two species
i s made.
The range o f 4 * sm lthii extends farther south in comparable a l t i ­
tudes than the range of 4 . c r ista turn.
The 1937 seed lo t of 4 . smith! i gave
a low i n i t ia l germination in September, probably due to the conditions of
harvest which made necessary a period of after-ripenin g o f the seed.
The seed of Agropyron pauciflorum was of northern origin from commercial
sources, obtained a year a fter harvest.
A 1935 seed l o t gave low germina-
tion during 1936-1937 (Tables 5 and 6 ).
The 193& seed lo t gave a fa ir ger­
mination during i t s second winter, but decreased in v ia b ility during 133S
(Table 10).
I f the ages of these seeds were correctly reported, the seed
o f th is species decreases rapidly in v ia b ility during i t s second year.
A
1937 seed lo t of Elyeras canadensis gave a fa ir germination in I t s f i r s t year
(Table 11).
Seed of a l l of the species of Hordeae reacted sim ilarly to tem­
perature and seasons as cool-temperature grasses.
Seed o f Bromus inermls was o f a lo c a lly adapted type secured each o f
the three years from the same f ie ld .
The seed lo t s gave a good germination
in a l l seasons o f the year except when temperatures were high, and retained
their v ia b ilit y well under the conditions of seed storage (F ig. 13)*
Al­
though only small increases in emergence of seedlings were secured by s o il
s te r iliz a tio n and l i t t l e seedling disease was encountered in these te s ts ,
the seedlings made an exceptionally better growth in s te r iliz e d s o il.
Seed of D actylis glomerata was obtained from commercial sources.
This
sp ecies has some ch aracteristics which make i t intermediate in c la s sific a tio n
as a cool-temperature or warm-temperature grass.
In the f i e l d i t is la te r
to begin growth in the spring than some of the cool-temperature grasses.
R ep ro d u ced with p erm ission o f the copyright ow ner. Further reproduction prohibited w ithout p erm ission.
Seedlings w in ter-k ill e a sily in the m id-latitude climate of Nebraska.
On
the basis o f handling the seedlings in the greenhouse, however, i t was in­
cluded with the coo1 -temperature group.
The best type of seedling growth
was obtained under r e la tiv e ly cool-temperatures.
Germination o f the seed
was low under the high temperatures o f the summer months* lik e that of the
other cool*temperature grass seeds ( f i g . 16).
Fluctuations in the germina­
tion of new seed indicate the s e n s itiv ity o f th is seed to environmental
conditions.
Uhder the same storage conditions as those for the seed of
Broans inermis the v ia b ilit y o f the 1935 seed was rapidly lo s t during the
summer o f 1937* In I t s second year after harvest.
Continued low germina­
tions were obtained during 1938* i t s third year a fter harvest.
The 1936
seed lo t also gave lowered germination in the summer o f 193®* i s i t s sec­
ond year a fter harvest, but regained a high percentage o f germination fo l­
lowing the summer months.
A commercial, medium-quality sample of Foa pratensls seed reported to
be from the 193& harvest was Included in the te s ts beginning in the f a l l
o f 1937 (Table 10).
Although th is seed was cleaned free of u n fille d glumes,
i t gave poor percentages o f germination in c o m p a ris o n with two selectio n s
o f nursery-grown seed of the 1937 harvest.
These two se lectio n s gave ex­
c e lle n t germination in s te r iliz e d s o il during the winter months but fa ile d
to germinate a t a l l under the h i^ i temperatures of midsummer (Table 11).
The seed of Phalarla arundinacea grown in Minnesota was obtained from
the same sources for each of the three years' harvests.
This species gave
somewhat erra tic seed germination sim ilar to that o f D actylis glomerata in
the month-to-month te s ts (F ig. 17)•
The 193& seed exhibited secondary
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dormancy in i t s f i r s t winter, and emerged from i t with progressive increases
in germination during the follow ing spring and strainer months despite the
high temperatures.
She 1935 seed exhibited sim ilar trends daring the same
months hut gave lower germinations as the temperatures were raised.
Losses
o f v ia b ility under the conditions o f seed storage occurred in the second
and third years with th is seed l o t .
fhe 1937 seed l o t also gave a lowered
germination during i t s f i r s t winter but the temperatures during the summer
of 193S were too high for continued higb. germinations.
Seed germination of the warm-temperature grasses.-—Seed o f Bouteloua
curtipendula was obtained from native grasslands in Holt County, Nebraska
la 1935*
Ihe other two lo t s were nursery-grown (fab les 9» 10* H ) •
fhe
seed o f th is sp ecies is subject to low germination as determined by emer­
gence from u n sterilized s o il; the seedlings were also subject to a type o f
Hdamping o f f B a fter emergence,
fable 6 shows th is species to be me of
those which p r o fits most by germination in s te r iliz e d s o i l .
In the monthly germination t e s t s , high percentages o f germination were
obtained during the la te winter and early spring months (Tig. IS ).
D iffer­
ences shown in the warm-temperature te s t (fab le S) indicate that somewhat
higher germination percentages could have been obtained during the winter
months i f a higher temperature had been employed.
Although th is was borne
out in the second winter, other factors appear to be Involved than the
temperature of the germination period,
fhe 1SJ6 and 1937 seed lo ts exhibit­
ed a primary dormancy and required a period o f after-ripenin g follow ing har­
v e st before maximum germinations were obtained.
Reductions in germination
occurred In the months follow ing months of high maximum and minimum tempera­
tures in both summers.
Germinations were lowest during the months o f July,
R ep ro d u ced with p erm ission o f the copyright ow ner. Further reproduction prohibited w ithout p erm ission.
August* and September of 1937* but were Increased for the 1936 seed follow ­
ing the September low minimum temperatures.
In the summer o f 1938, the
temperatures were high for six consecutive months resu ltin g in continued
lowering o f germination.
As the seed aged* the fluctuation caused by these
changes in external conditions was le s s v io le n t.
The 1935 seed retained
a r e la tiv e ly high percentage o f germination through i t s third summer. B lot­
ter germinations under standard-temperature conditions (20° to 30° C») show­
ed the same trends in decreasing v ia b ility at a l i t t l e higher percentage
than the s o il germination.
Seed lo t s o f Bouteloua g r a c ilis were secured from areas of native
grasslands in Holt County in both 1935 and 1937*
Two nursery-grown lo t s
o f seed were harvested
for the t e s t s , in 1936.
These four seed
lo t s gave
b est germinations from
January to May in both years of the te s ts (Fig. 19) •
Germination was lowered during and follow ing months o f excessively high tem­
perature,
Short- periods o f after-ripening follow ing harvest were required
for the 1936 and 1937 seeds to reach their maximum germinations.
The sec­
ond l o t of 1936 seed, tested only in i t s second year, gave a higher ger­
mination for that period than the one shown in the graph ( Table 10).
resu ltin g germinations a t the end o f the period were quite sim ilar.
The
Both
o f these 1936 seed lo t s lo s t their v ia b ility more rapidly than the seed
from the 1935 harvest had done
Seed o f Bouteloua
at a sim ilar age.
hlrsuta gave low germinations throughout mosto f
the period (Tables 9, 10, and 11} and Fig. 20).
secured from S tillw a ter, Oklahoma.
The 1935 seed lo t was
Ihe other two lo t s were seed increase
from a planting of th is original seed.
The seed lo t s required a long period
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53
o f after-ripening to attain a maximum germination.
They responded only
s lig h tly to the high tessera tares in the te s ts reported in Table 8, hut
had ripened to give th eir highest germination during the hot summer months.
That the increased germination was not due to the temperature of the ger­
mination period i s indicated by the standard-temperature b lo tte r te s ts which
coincide clo sely with the s o il germination t e s t s .
This ind icates that the
cause o f the low germination was due to conditions within the seed rather
than to unfavorable environmental fa cto rs.
The 1937 seed l o t , although
from the sane plan ts as the 193^ seed, gave a higher germination than the
other two lo t s .
Seed from two years* harvests o f Buchloe dactyloides were used in the
te sts.
The 1935 l o t was machine harvested in Oklahoma (Table 9 ).
Germina­
tion te s ts of 1936 seed were run with two small hand-collected lo t s secured
from the same f i e l d near Holdredge, Nebraska (fa b le 10).
sim ilar germinations the data i s graphed as one l o t .
Since these gave
These seed lo ts gave
somewhat erra tic germinations between 3® a»d 60 per cent for most o f the
period (F ig. 21).
f i r s t spring.
The 1936 seed increased in emergence with age during the
She hi$a temperatures of May, 1937* and March, 1938* caused
downward trends in germination which did not turn upward sharply u n til cool
September.
A considerable percentage o f the seed fa ile d to germinate in
a l l te s t s .
B lotter te s ts were sim ilarly e r r a tic , the 1935 seed giving the
highest t e s t .
S ix l o t s o f seed o f Andropogon fu rc a tu s were in clu d ed in the t e s t s .
The 1935 seed l o t was a c o lle c t io n from a n a tiv e meadow in H olt County,
Nebraska (Table 9)»
The f i r s t l o t o f 193& seed was from a n a tiv e meadow
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in the P la t t e T a lle y near M axwell, Nebraska (T able 10),
This seed l o t l o s t
i t s v i a b i l i t y in the gammer o f 19 J 8 and the data from a second 1S3& l o t o f
nursery-grown seed was s u b s titu te d to p r e se n t the sea so n a l trends in the
graph.
Three l o t s o f 1937 seed in the same order a s l i s t e d in Table 11,
were secured a s fo llo w s :
A la r g e -se e d e d l o t was secured by com positing seed
o f a number o f nursery-grown s e le c t io n s ; th e second l o t was secured from a
la rg e s c a le h a r v e st from meadows in H olt County, Nebraska; and a la r g e seeded s e le c t io n was secured from Woodward, Oklahoma.
a co n sid era b le v a r ia tio n in seed s i z e .
These l o t s e x h ib ite d
The seed from the n a tiv e meadows
averaged much sm aller than the nursery-grown seed .
A number o f problems are p resen ted in the germ ination o f th e seed and
in the estab lish m en t o f se e d lin g s o f the two Andropogon s p e c ie s .
The seeds
o f th e se s p e c ie s fr e q u e n tly g iv e a poor germ ination under greenhouse con­
d it io n s .
S eed lin g emergence i s freq u en tly slo w , p a r tic u la r ly during the
w inter months.
Germination in u n s t e r iliz e d s o i l , when o th er fa c to r s fo r
germ ination are a ls o u n favorable, may r e s u lt in near f a ilu r e in secu rin g
s e e d lin g s from sm all q u a n titie s o f seed .
L osses are c h ie f ly due to f a ilu r e
o f emergence o f the s e e d lin g s , ra th er than l o s s o f se e d lin g s a f t e r emergence.
Although the seed s imbibe w ater, they may f a i l to germ inate in the s o i l .
The r e s u lt i s a so fte n in g and r o ttin g o f the seed w ithout emergence o f the
s e e d lin g from the seed c o a ts .
To what e x te n t the f a ilu r e to germinate i s
due to s u s c e p t i b ilit y to d is e a se organisms as co n tra sted to causes w ith in
the seed i t s e l f or i t s s o i l environment, have n o t been determ ined.
Germina­
tio n in s t e r i l i z e d s o i l gave marked in c r e a se s in s e e d lin g emergence (Table 6 ) .
Seed germ ination and s e e d lin g esta b lish m en t o f Andropogon fu rca tu s under
the e x is t in g greenhouse c o n d itio n s were com paratively h igh in th e months o f
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February, March, A pril, and. May in "both years of the te s ts (P ig. 22).
Stand­
ard-temperature b lo tte r te s ts gave much higher germinations than s o il t e s t s .
Tests under d ifferen t temperatures indicate that the seed should be germina­
ted under r e la tiv e ly warm conditions in the greenhouse (Tables 7 and S).
However, the lowered germinations during the winter months cannot be en tire­
ly explained by the cool temperatures o f these months, since high germina­
tion s were also secured a t sim ilarly low temperatures of the f a l l months.
Low germinations also were secured as a r esu lt o f one or more months of
high temperatures.
These fluctuations point to cumulative month-to-month
changes in the v i t a li t y of the seed which resu lt in fa ilu re o f seedlings
to emerge in s o il even though r e la tiv e ly high germinations in b lo tter te s ts
may be secured in those months.
Higher germinations were secured with the
large-seeded nursery-grown selectio n s o f 193& and 1937 seed recorded on the
graph, than with those secured with the seed from native meadows in the same
years.
Pour lo t s of seed o f Andropogon scoparius were secured as follow s:
The
1935 lo t and the f i r s t lo t o f 1937 seed were c o llected from native meadows
o f Holt County; the 193^ seed was nursery-grown; the second lo t o f 1937 seed
was a selectio n from Manhattan, Kansas.
lo t s were small.
The earyopses o f a l l o f these seed
Seed o f Andropogon scoparius gave germination resu lts sim­
ila r to those of the small-seeded co llec tio n s o f Andropogon fureatus seed
in the seasonal trends of germination (P ig, 23).
Germination was greatly
increased by s o il s te r iliz a tio n (Tables 5 aud 6) and by warm temperatures
(Tables 7 and g ).
The 193& seed lo t was not of su ffic ie n t size after re­
cleaning to secure seed for the entire series of t e s ts .
Bather low ger­
minations and early lo s s of v ia b ility were secured with these seed lo t s .
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Che 1935 seed lo t o f Sorghastrum nutans was machine harvested in Holt
County* Nebraska (fable 9 ).
The 1936 seed was harvested from nursery-grown
se le c tio n s, but in su ffic ie n t seed was obtained for the complete series of
monthly te s ts (fa b le 10).
fhe f i r s t lo t of 1937 seed was nursery-grown in­
crease o f the 1935 seed, the second lo t was a co llec tio n from a native mead­
ow in Holt County, Nebraska, and the third lo t was from Woodward, Oklahoma
(fa b le 11).
fhe seed of Sorghastrum nutans displays a peculiar type of dormancy
(P ig. 2k ) .
Low percentages of emergence o f seedlings from s o il are appar­
ently not due to d isease, although, smal l increases in emergence were secured
in s te r iliz e d over u n sterilized s o il (fable 6 and Pig. 2ty).
fhe 1935 seed
gave low germination in the standard monthly s o il te s t s , with the only break
(60 per cent germination) occurring in September, 1937* a month of low tem­
peratures.
fhe comparatively high, germination o f 25 per cent in October,
1936, in the greenhouse was increased to i+2 per cent in the coldframes ger­
mination because of the low minimum temperature (fa b le J ) ,
fhe 1936 seed
lo t germinated 55 per cent in October a fter harvest, while the 1937 seed
required a period o f ripening a fte r harvest before high germinations were
secured the follow ing spring.
Seed of a l l three lo t s went into winter dor­
mancy with germination at the lowest during December.
Although low minimum
temperatures appear to increase germination, th is species i s included with
the warm-temperature grasses,
fhe su ita b ility of th is c la s sific a tio n i s
borne out by the effectiv en ess o f germination under warm temperatures a fter
p r e ch illin g of the seed, by the warm temperatures required for best seedling
growth and establishment in the f i e l d , and by the taxonomic relationship of
the species with the bluestems.
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Seed o f Panicum virgatum gave some of the most In terestin g and con sist­
ent germination records for the monthly t e s ts .
Five lo t s of seed were includ­
ed and are reported for these monthly t e s t s , and additional data has also
been obtained with seed from numerous selectio n s and sources.
The origin al
1935 seed was a sample from a machine-harvested l o t secured in Holt County,
Nebraska (Table 9 ).
The 193& seed lo t was from a group of nursery-grown
se lec tio n s of lo c a l type (Table 10).
Seed lo t s from the 1937 harvest were
secured in the same order as given in Table 11, as follows?
A nursery-grown
increase o f the 1935 seed lo t; a seed lo t from a Holt County meadow; and a
seed lo t from Woodward, Oklahoma.
Tests have also been conducted with seed
from Mandan, North Dakota.
The seed o f Panicum virgatum seldom gives large increases in emergence
o f seedlings as the resu lt of s te r iliz a tio n o f s o il (Table 6 ).
In the prac­
tic e o f growing seed lin gs, however, s o il s te r iliz a tio n has been found ad­
vantageous in securing the establishment o f seed lin gs.
Although th is was
not shown in the te s ts of the e ffe c ts of s o il s te r iliz a tio n , a seedling
disease has developed in u n sterilized s o il which resulted in a serious lo ss
o f the seedlings several weeks a fter emergence.
The resu lts o f the greenhouse germination in s te r iliz e d s o il of the
first-named l o t in each of the tables (Tables 9* 10, 11) are presented
graphically in Figure 25.
The three lo ts reacted sim ilarly *feen the same
ages o f seed are compared on the graph.
The older 1935 seed gave a regular
seasonal response with r e la tiv e ly high germination during the spring and
f a l l months.
Lowered germination during the summer appears to be due to
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the cumulative e ffe c t of the high temperatures of the period of months.
The
seed went into dormancy during the months o f October to February inclu sive
in both years, although the variations in germination are le s s as the seed
ages,
fhe periodic rhythm o f germination appears to e x is t, however, in asso­
ciation with the changing environmental conditions of season,
fhe 1936 and
1937 seed lo t s required a long period o f ripening before giving a sa tis­
factory germination,
fh is occurred in September a year a fte r harvest.
Sim­
ila r r esu lts were recorded with the other two lo ts reported in fable 11, and
a lo t o f seed from Mandan, Sforth Dakota also showed th is response.
fhat these changes in germination are not due e n tirely to changes in
temperature o f the germination periods in the greenhouse i s shown by the
b lo tte r germinations.
She r esu lts with the 193& a*.d 1937 seed in b lo tte r
te s ts conducted a t standard germination tenq>eratures showed the same trend
o f emergence from winter dormancy with the 193& seed, and the same increases
in germination of the 1937 seed as the resu lt of after-ripenin g processes,
fhe fluctuations from the general trend in the s o il germinations show the
modifying e ffe c t o f the greenhouse environmental conditions on the processes
going on in the seed i t s e l f ,
fhe p oten tial germination of th is seed is high,
as i s shown in the subsequent te s ts ,
fhe occurrence of dormancy makes for
seed o f considerable longevity.
Seed of the dropseeds. Spqrobolus spp., presented a s t i l l d ifferen t
combination o f problems of germination, emergence and establishment o f seed­
lin g s , and seed dormancy.
tested ,
Five lo t s of seed of Sporobolus airoides were
fhe 1935 aud 193& l o t s , and the f i r s t lo t o f 1937 seed were from
la rg e-scale harvests from native grasslands in the P la tte Talley near
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Oshkosh, Nebraska (fab les 9» 10, and 11 and f ig . 26).
In graphing the re­
su lts of germination of the 1937 seed lo ts of Andropogon furcatus. Sorghastrum nutans, and Panicum virgatum, the data of the highest germinating seed
lo t s were used.
These were nursery-grown.
The second lo t of 1937 seed of
Sporobolus airoides was nursery-grown increase of the 1935 seed.
It gave
somewhat higher germination than the f i r s t lo t but the data was not pre­
sented in the graph because of c o n flic t with the lin e of the 1936 seed.
The third lo t of 1937 seed was obtained from Woodward, Oklahoma.
Sporobolus airoides seedlings are susceptible to diseases in green­
house s o ils .
In u n sterilized s o i l , lo sse s of seedlings resulted both from
fa ilu re o f emergence and from the death of the seedlings a fter emergence,
as compared to germinations in s te r iliz e d s o il (Table 6 ).
The germination of Sporobolus airoides in s te r iliz e d s o il was high
during March, A pril, May, and June with a somewhat lowered germination
during the months o f excessively high temperatures in the greenhouse (P ig.
26).
fhe graph presents a sim ilar winter dormancy for the months of Octo­
ber to February, as was shown for Panicum virgatum.
A fter-ripening pro­
cesses in the 193& and 1937 seed increased the germination in the spring
follow ing the year of harvest.
The 1935 a^d 1936 seed gave sim ilar lowered
germinations during their respective second winters, as did new seed in
its fir s t.
This suggests that the older seed was going through the same
«
processes as was the new seed.
That these e ffe c ts were not due alone to
the temperatures during the germination period, i s shown by the standardtemperature b lo tte r te s ts which gave similar trends of increasing germina­
tion in the monthly te sts follow ing the low germination period o f midwinter
(P ig. 26).
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Seed of SporoboluB eryptandrus was secured in 1935» as a secondary seed
In a harvest o f the native grass Bouteloua g r a c ilis * The 1936 and 1937 seed
lo t s were harvested froia a nursery planting of the 1935 seed (Tables 9» 10
and 11).
The seed co llected in 1935 gave poor germination during most of
the two-year period (F ig. 27).
The nursery-grown seed lo t s gave higher ger­
minations than the original seed l o t , but with sim ilar trends in dormancy.
Newly harvested seed have higher germinations follow ing harvest than in
la te r months, with both 1936 and 1937 seed.
Changes in the seed follow ing
harvest caused the seed o f a l l three lo t s to become dormant during early
winter, while the trend of germination became gradually higher through the
spring and early summer months.
This gradual trend was broken by the rel­
a tiv e ly high germinations brought about by the favorable greenhouse condi­
tio n s in the months of February, A pril, Hay, and June of 1937* and in the
months of March, A pril, May, and June of 1938*
Accordingly, seedlings may
be obtained for propagation by planting seed during la te spring*
Standard-
temperature germinations on b lo tte r s fa ile d to give any indications of the
true v ia b ilit y o f the seed (F ig. 27).
Dormancy of grass seeds. —The fundamental causes of seed dormancy have
been analyzed by Crocker ( S) .
The external and internal causes a ffectin g
the delayed germination of seeds have been reviewed in relation to plant
establishment by Weaver and Clements (2S).
Evidence has been presented by
several investigators to indicate the causes o f dormancy in grass seeds.
Many of the grass seeds exhibit periodic dormancy due to seed coat r e str ic ­
tio n s preventing gaseous exchange (2 , 3, S, 12, 20, 22).
The d iffic u lty o f
ascribing fa ilu re to germinate to any one cause within the seeds, even
though the sh iftin g optimum external conditions for germination can be given,
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6l
h as te e n noted by Toole (2 1 ) .
A few in v e s tig a to r s hare shown th a t dormancy
in seeds due to seed coat r e s t r ic t i o n s may "be com plicated by embryo dormancy
as w e ll (1 0 , 2 2 ).
Atwood (3 ) conducted s tu d ie s on the ab sorp tion o f oxygen by seeds o f
Avena fa tu a under d if f e r e n t oxygen p ressu res and during d if f e r e n t tim es o f
the y e a r .
The seed s o f t h i s s p e c ie s norm ally gave h i^ ie r germ inations during
the sp rin g than during December.
In the experim ents, in c r ea se d p ercen tages
o f germ ination were obtained in hlg^i oxygen co n cen tra tio n s w ith seared seed s
than w ith in t a c t se e d s.
High oxygen co n cen tra tio n s in c r ea se d th e germ ination
o f the Avena fa tu a seeds in both autumn and sp rin g but to a g rea ter e x te n t
subsequent to th e p e r io d o f a fte r -r ip e n in g .
H arrington (12) s t a t e s th a t the embryos o f wheat, o a t s , and b a rley are
never e s s e n t ia ll y dormant, but th a t dormancy i s imposed by seed coat r e s t r i c ­
t io n s .
Increased oxygen p r e ssu r e s were e f f e c t i v e in in c r e a sin g germ ination.
Anderson (2 ) in crea sed the germ ination o f Poa compressa by su b je c tin g the
seed to atmospheres o f carbon d io x id e or o f n itr o g e n .
Toole (22) rep o rts
th a t I n v e s tig a tio n s on the seed dormancy o f O ryzopsis hymeaoides show i t
to be due to m echanical and embryo dormancy but w ithout a sharp d is t in c t io n
between them.
E xclu sion o f oxygen was rep orted as the cause p rev en tin g
germ ination, b u t c e r ta in typ es o f the 0 . hymenoides seed s a ls o contained
dormant embryos.
Seed o f each o f the g r a sse s in t h is study showed low ered germ ination
due to season al change o f some environm ental fa c to r in the greenhouse.
Temperature seemed to be the most important f a c t o r .
E x c e s siv e ly high
tem peratures o f the summer germ ination p e r io d s caused low ered germ ination
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with one or more seed lo t s o f a l l o f the grasses.
Low temperatures daring
the winter germination periods were shown to lower the germination o f seeds
o f some of the warm-temperatare grasses.
Seed o f most of the grasses showed trends in germination due to processes
within the seed.
Gontinaed high temperatures from month to month daring the
summer months appeared to a ffe c t the seed in storage to cause a continued
lowering of germination in s o i l .
Sim ilarly, trends of lowered germination
ex isted during the winter months which cannot he explained on the basis of
the temperatures of the germination periods.
This was le s s pronounced with
several of the cool-temperature grasses.
The cool-teuperatare grasses gave high seed germinations within r e l­
a tiv e ly short periods after the harvest of normally field -rip en ed seed.
few seed lo ts required a period of after-ripenin g.
A
Any short period of
after-ripenin g did not show in these te s ts because o f the time which elapsed
between harvest and the f i r s t germination te s t .
With the cultivated sp ecies,
i t might be e j e c t e d that there would be a lessened tendency for protracted
seed dormancy.
In most cases the co o1 -1enpe ra tur e grasses are also adapted
to seeding and establishment in the f a l l follow ing harvest.
Seeds of the warm-tenperature grasses as a group, displayed more tend­
encies fo r delayed germination than seeds o f the cool-tenperature grasses.
Primary dormancy of the seed was shown in the comparatively low in it ia l ger­
mination in one or more seed lo t s o f a l l o f these sp ecies.
With d ifferin g
periods of after-ripening the seed lo t s in many cases gave very good ger­
mination.
For two o f the gramas, Bouteloua curtipendula and B. g r a c ilis ,
the two bluestems, Andronoaon furcatus and 4» scoparius, and for Sporobolus
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a ir o id e s . the r e la t iv e l y h ig h e s t germ inations were secured in e a r ly sp rin g
fo llo w in g the year o f h a r v e st.
Other s p e c ie s showed p r o tr a c ted seed dor­
mancy in one or more seed l o t s and lo n g p e r io d s o f a fte r -r ip e n in g were re­
qu ired b efo re h ig h germ inations under the d e scrib ed greenhouse environment
were ob tain ed .
Seeds o f most o f the warm-temperature g r a sse s germ inated
w e ll w ith the wide ranges o f com paratively warm tem peratures during the
sp rin g months.
Seed o f a few s p e c ie s such a s Panicum virgatum . Sorghastrum
n u ta n s. Kid Sporobolus a ir o id e s . a t one time or an oth er, responded to wide
ranges o f tem peratures w ith low minimum tem peratures.
Atwood (3 ) s t a t e s th at the teaperature a t which seed s w i l l germinate
i s a measure o f the degree o f a ft e r -r ip e n in g .
I f seed s w i l l germinate o n ly
w ith low minimum ten p era tu res, a lo n g er p e r io d o f r ip e n in g i s n ecessa ry ; i f
seed s w ill grow a t
C.» then a fte r -r ip e n in g i s c o u p le te .
Toole (22) has
shown the e f f e c t o f seed sto ra g e a t h i # tem peratures ( 3O0 C .) in in crea s­
in g the v i a b i l i t y o f O ryzopsls hyaenoid es.
The e f f e c t o f low tenp eratu res
on dormant m oistened seed have been e f f e c t iv e in in c r e a sin g germ ination
where the r e s t r ic t io n s were in the seed c o a ts a s shown by Harrington (1 2 )
and by Toole ( 2 1 ) , and ifeere changes in the embryo were req u ired as shown
by D avis ( 1 0 ) .
E thylene ehlorohydrin has been used in breaking dormancy
in p la n t p a r ts ( 3 1 ) .
Seeds o f S o rg h a s tru m n u t a n s . P an icu m virgatum . Sporobolus a ir o id e s .
and J . crypt an drus e x h ib it typ es o f dormancy w ith in v a r ia b ly low germ inations
during the w inter months under the u sual germ ination c o n d itio n s .
The h i #
September germ inations o f the seed o f the f i r s t two s p e c ie s occurred a f t e r
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6k
a storage p e r io d o f warm temperatures during the summer months and during
a fa v o ra b le germ ination p e r io d w ith low minimum tem peratures.
Since low minimum tem peratures d id n o t occur in the greenhouse during
the sp rin g , h i^ i germ inations o f Panicum virgatum were n o t then obtained
in the monthly t e s t s .
Seed in i t s second and th ir d year gave a b e tte r ger­
m ination during the sp rin g months, sin c e i t s low minimum-temperature req u ire­
ment had been r a is e d by the a fte r -r ip e n in g p r o c e s s e s .
Seed o f Sporobolus
a ir o id e s ripened more r a p id ly than Panicum virgatum to g iv e v ery high ger­
m inations in e a r ly spring*
fh e trends in germ ination o f a p o r tio n o f the newly h a rv ested seed o f
Sporobolus oryptandrus d if f e r somewhat from those o f the p r e v io u sly d isc u sse d
s p e c ie s w ith p r o tr a c te d dormancy,
A la rg e p ercen tage o f the seeds in a l l
t e s t s appeared to be in a deep s t a t e o f primary dormancy.
However, both
the 1936 and 1937 seed l o t s gave h ig h er germ ination in the f i r s t t e s t s f o l fow ing h a rv est than in la t e r months,
f h is appears to be an adap tation fo r
immediate summer germ ination and s e e d lin g esta b lish m en t fo llo w in g summer
seed p rod u ction , sin c e the seed s germinate w e ll under h igh ten p era tu res,
fh e trends o f d ecrea sin g germ ination in the new seed fo llo w c lo s e ly the
secondary dormancy e x h ib ite d by one-year and tw o -y ea r-o ld see d ,
f h is p o in ts
again to the cum ulative e f f e c t o f environm ental fa c to r s on the seed fo llo w ­
in g h a r v e st and during sto r a g e , s in c e l i t t l e change occurred in the tempera­
tu res during th ese p e r io d s o f changes in germ ination,
fh e seed o f a l l l o t s
showed a d e f in it e p e r io d ic rhythm o f v i a b i l i t y , broken o n ly by the a c tio n
o f favorab le fa c to r s on the germ ination during the sp rin g months.
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E ffects o f refrigeration and chemical treatments. —A planting was made
on December 3, 193& to te s t the e ffe c t of controlled c h illin g in increasing
the germination of dormant seed.
The previous germination te s ts with low
minimum temperatures had indicated that the seed o f Sorghastrum nutans.
Panicum virgatum. and Sporobolus a iroid es. would respond to a p rech illin g
treatment for increasing germination.
Prom the same 1935 seed lo t s as those
used for the monthly germination t e s ts . 200 seeds were counted out in trip ­
lic a t e and placed in glass v ia ls p a r tia lly f i l l e d with p eat.
At weekly
in terv a ls, beginning four weeks before the planting date, the tr ip lic a tio n s
o f peat>-eovered seed o f the three species were thoroughly moistened and
placed in a household refrigerator, operating a t approximately to0 P.
These
v ia ls were l e f t in the refrigerator continuously for the four d ifferen t pe­
riod s.
Another s e t o f tr ip lic a tio n s was given a refrigeration treatment for
alternate in tervals of 12 hours each, during a two-week period prior to the
planting date.
She r e su lts in comparison with soaked and dry check treat­
ments (fable 12) indicate that the longer periods of three and four weeks
o f c h illin g were the most e ffe c tiv e .
A sim ilar te s t was run with 193& seed o f the same three species planted
February 27, 1937 (fab le 13) .
Seeds of Lot 1, Panicum virgatum and Lot 1,
Sporobolus airoides were from the seed lo t s used in the monthly germination
te s ts and for which the data are presented in graphic form in Figures 25
and 26.
fhe Lot 2 Sorghastrum nutans and Lot 2 Panicum virgatum were addi­
tion al seed lo ts for which no other data are presented,
fhe 193& seed, lo t s
gave sim ilar r esu lts to those of the 1935 seed lo t s planted the previous
December,
fhe three-week period o f p r ech illin g gave the highest resu lts
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Table 12,—E ffect ©f seed treatment by refrigeration i / on seed germination and seedling establish­
ment o f three native forage grasses - Sorgfaastma nutans. Panicum virgatum. and Sporobolus a iroid es.
Seed from the 1935 harvest planted in s te r iliz e d s o i l , December g, 1936. _____
Seed treatment
prior to germination
Dry check
Soaked one week
Sorghastrum nutans
Panicum virgatum
Sporobolus airoides
.Emergence .Establishment .Emergence .Establishment .Emergence .Establishment
P .c t.
P .c t.
P .c t.
P .c t.
P .c t.
P .c t.
15
20
2©
26
15
23
26
26
21
20
Ik
13
15
Ik
21
18
9
9
One week
51
51
25
25
37
37
Two weeks
56
56
ks
kj
ks
ito
Baree weeks
6l
61
53
52
sg
51
four weeks
&
St
50
50
Alternate refrigeration
for 12-hour periods
Two weeks
Continuous refrigeration
i / Seeds were placed in glass v ia ls f i l l e d with wet peat.
held at ^0° ?. except for periods of defrosting the machine.
Basse were placed in a refrigerator
!=J Thirty-three per cent of the seed began to sprout in the alternate refrigeration process,
but only fifte e n per cent emerged above the s o il a fter p lan tin g.
on
ON
67
Table 13. —E f fe c ts o f r e fr ig e r a tio n and chem ical treatm ents on th e seed
germ ination o f Sorgfcastrum n u tan s. Panicum virgatum . and Sporobolue
a ir o id e s . Seed from th e 1936 h a r v e st p la n te d February 27* 1937*
Seed treatment
prior to germination
Check;
*
Emergence o f seedling s
1Sorghastrum5
*Sporobolus
Panicum virgatum* airoides
* nutans
1 Lot 2
! Lot 1 : Lot 2 * Lot 1
P .c t.
P .c t.
P .c t.
P• c t.
14
1
2
58
Alternate refrigeration for
12-h r. periods
2S
16
13
42
One week
27
35
29
72
Two weeks
42
65
49
74
Three weeks
41
jg
60
M
Pour weeks
36
70
11
62
Soaked in water, 20 min.
Sat. atmos. 5©$, 24 hr s .
•»
3
4
♦♦
Soaked in 1$ s o l . , S min.
Sat* atmos. 1$, 24 hrs.
•♦
11
52
••
Soaked in % s o l ., S min.
Sat. atmos. 3$ s o l ., 24 hrs.
•a
58
49
♦«
Soaked in
sol . , g min.
Planted d ir ec tly to s o il
•e
1
3
••
One meek
Continuous refrigeration
Ethylene chlorhydrin
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fo r three o f the seed. lo t s .
Lot 1 Panicum virgatum and Lot 1 Sporobolus
airoid es gave higher germination with three weeks of p r e ch illin g than was
obtained with the December te s t o f 1935 seed.
In the case o f Sporobolus
airoides the check germination of the la te February planting exceeded the
germination obtained in the regular monthly te s t planted February 15.
fhe
58 per cent f a l l s in the lin e o f the increasing germination o f the ripen­
ing seed; the germination was increased 20 per cent by the three weeks of
refrigeration .
P rech illin g treatments as described were in e ffe c tiv e in in­
creasing gem ination o f Andropogon furcatns. Buchloe dactyloid es. and Sporo­
bolus cryptaadrus.
Data on a chemical treatment method of breaking the dormancy of Panicum
virgatum seed are also presented in fable 13.
Seed treatments of the same
seed lo t s of Panicum virgatum by soaking the seed in ethylene chlorhydrin
and exposing i t to ethylene chlorhydrin vapor were nearly as e ffe c tiv e as
the refrigeration treatments in increasing germination,
fhe treatment by
which the seed was soaked eight minutes in a one per cent solution of eth­
ylene chlorhydrin and then exposed to a saturated vapor over the same
strength of solution for 2^ hours gave the best resu lts for both seed lo ts*
fhe same treatments applied to a third lo t o f 193& seed of Sorghastrum
nutans and to seed of Andropogon furcatus. and Buchloe dactyloides were
in e ffe c tiv e .
Using 1937 seed, germination was increased by the refrigeration method
with seeds o f Sporobolus airoides and Panicum virgatum.
fhe f i r s t lo t of
1937 seed of Sporobolus airoides for which data are presented in fable 11,
gave only 32 per cent germination with two weeks o f refrigeration , but the
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second lo t o f seed with a sim ilar trend of monthly germination gave 57 per
cent with four weeks treatment in December, 1937» in a t e s t comparing periods
up to four weeks o f refrigeration (P ig. 26).
In th is te st the 1937 lo t of
Panicum virgatum required four weeks of treatment to reach 5^ per cent (P ig.
25).
Since the check in th is instance was one per cent corresponding to the
lin e o f the graph of monthly germinations, a 53 per cent increase was obtained.
Using the 1935 seed of S o r ia s tram nutans in the t e s t in December, 1937* &
germination of 58 per cent was secured with four weeks o f refrigeration as
compared to 6 per cent in the monthly te s t (P ig. 2*0.
In a l l te s ts o f the refrigeration treatment, Panicum virgatum responded
with the b est r e su lts.
In March, 1938* seed of 145 se lec tio n s of Panicum
virgatum from the same f ie ld o f plan ts from which the 1937 seed lo t for
monthly germination te s ts was obtained, gave an average germination of 64
per cent with three weeks o f refrigeration as compared to a check of 3 per
cent.
Prom these germinations over 5000 seedlings were space-planted to
the f i e l d in early May,
These plants made su ffic ie n t growth to produce
a good seed crop in September, 1938.
Had they been a month la te r in estab­
lishment in the f i e l d , another year would have been required to make seed.
Many o f the se lec tio n s would have been lo s t i f they had been germinated
without treatment or i t would have been necessary to hold the seed a year
before planting.
S eed lin g E stablishm ent and Growth
E ffects o f plant bands and s o il mixtures.--G rass seedlings may be grown
in s o il f la t s with or without paper bands.
She fin e fibrous root systems of
many o f the sp ecies make i t necessary to separate the seedlings as Individ-
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u a ls early in their growth, in order to retain the id en tity o f the individ­
ual seed lin gs.
Whether or not hands are used, the even spacing of the seed­
lin g s within the f l a t i s desirable to secure a uniform and adequate growth
for transplanting.
Bands have been used advantageously in securing a uni­
formity o f transplanting to nonirrigated lands.
Grass seedlings have “been grown in hands of various grades o f manila
and tough white papers, and asphalt f e l t roofing paper.
Although the
former untreated .peepers are more e a sily cut and are cheaper, they d isin te­
grate too rapidly, allowing the individual plants to grow together before
the seedlings have gained an adequate age fo r transplanting to dry-land
conditions.
Seedling growth is usually retarded by the lack o f nitrogenous
m aterials made unavailable by the growth of the organisms causing the d is­
integration.
Asphalt f e l t paper bands, being more r e sista n t to decay, have
been more sa tisfa c to ry .
Che 15-pound weight per square has been used ex­
ten siv ely , but the 12-pound weight has been found easier to use and some­
what cheaper.
For the te s ts of seedling growth, Bromus inermis and Bouteloua g r a c ilis
were selected as representative of the cool-temperature group and warm-tem­
perature group of grasses, resp ectively.
Paring the spring o f 1937* seed­
lin g s were grown in three siz e s o f asphalt f e l t bands s
1-3/4" x 1-3/4" x 4",
2" x 2" x 4", and 2- 1/ 2" ± 2- 1/ 2" x 4", with 96, 77, and 54 p lan ts, respec­
tiv e ly per f l a t , using a s o il of fiv e parts s i l t loam to one part o f sand,
fable 14 shows the e ffe c ts o f the siz e of the band on the number of shoots
produced per p la n t.
She growth in the large bands ( i f the plan ts are grown
fo r two months or over) i s pronounced and the e ffe c t is noticeable in the
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Table I**.—E ffect of size of plant band on the growth of seedlings of Bromus inermis and
Bouteloua g r a c ilis in the greenhouse. Average number o f shoots per plant produced by
three-month-old seedlings grown in a mixture of fiv e parts s o il and one part of sand.
) S a a ll bands, if " x if" Medium bands, 2" x 2" Large bands, 2g-H x 2 | B
5% p la n ts
77 p l a i t s
'
96 p la n ts
Ave. No. sh oots
Ave. No. sh o o ts
•
Ave. No. shoots
S p ecies
Bromus inerais
1*7
2.U
Bouteloua g r a c ilis _____________U.7__________________ 6.0__________________ 7.8
Table 15. —E ffects o f kind of s o il mixture on the growth o f seedlings of Bromus inermis and Bouteloua
g r a c ilis in the greenhouse. Average number o f shoots and growth ch aracteristics produced by 24
three-month-old seedlings grown in small plant bands.
•
) Bromus inermis
Bouteloua g r a c ilis
Color
Shoots >
Growth habit and
j Shoots :
Soil Mixture
of
per
5 condition of seedlings
{ per ;
plant :
: plant ; seedlings
Ave. Ho.
Ave. l o .
Parts by volume
5 p ts . s o il, 1
S ilt loam s o il
5 p ts . s o il, 1
p ts. s o il,
p ts . s o il,
p ts . s o i l ,
p ts. s o il,
•pts. s o il.
2 .0
p t. sand
p t,
p t.
p t.
p t.
p t.
p t.
sand, 1 pt. peat
sand.l pt. manure
manure
commercial compost
sand, 1 p t. compost
sand. 2 p ts . manure
2.6
2.6
h.9
5.0
___
yellow-green
yellow-green
yellow-green
pale green
green
dark green
dark green
dark green
3 .3
Irect; leaves dying
1*.0
Irect; fa ir growth
5*6
Erect; leaves dying
5.3
Erect; good plants
8.1*
Semi-erect; good plants
8 .6
Semi-erect; good plants
10.3
Semi-erect; good plants
6.'*____ Erect; good plants______
transplanted plan ts in the f ie ld throughout the f i r s t season under dry-land
conditions.
For p ra ctica l purposes, the small 1-3/4" x 1-3/4" hands are
more conservative of greenhouse space and w ill carry plants for a l i t t l e
over two months using only an ordinary s o i l .
With the addition of more
nutrient m aterials to the s o i l , r e su lts approaching or surpassing those for
larger containers o f ordinary s o il can he secured.
The e ffe c t o f the degree o f f e r t i l i t y on seedling growth was shown in
another t e s t with seedlings o f the same two sp ecies.
e ffe c t on plant growth produced.
Table 15 shows the
The s o il mixtures lis t e d in the tahle are
arranged in the order of their increasing effe ctiv e n e ss in producing good
growth as measured hy the average number of shoots per p lan t, the e ffe c t
on the seedlings of the two sp ecies being quite con sisten t.
The various ingredients in the s o il mixtures made p ossib le an increas­
ing quantity of nutrients available to the seed lin gs.
The commercial peat
seemed to be low in immediately available nu trients; the o ld , w ell-rotted ,
fin e ly pulverized manure was about equal in nutrients to a commercial fer ­
t i l i z e r compost.
Although the addition of sand diluted the concentration
o f the n u trien ts, the data seem to indicate that the addition o f sand is
desirable with large q u antities of manure or commercial f e r t iliz e r .
S oil
mixtures with manure or the commercial compost alone, tended to become
water f i l l e d .
The commercial compost appears to have had some readily
available nutrient materials included which e sp e cia lly favored the growth
o f the seedlings o f Bouteloua g r a c ilis when mixed in the proportions with
sand.
The number o f shoots o f Bouteloua g r a c ilis in the s o i l mixture with
two parts of manure and one sand was lower than for eith er o f the mixtures
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containing comport.
Sinee the number was only one larger than that for the
mixture containing one part of manure and one part sand, i t appears that
the lim its of return in growth due to added increments o f manure was approach­
ed.
The rather slow a v a ila b ility of the nutrient m aterials of the manure
for "both sp ecies, was also indicated "by the growth of the seedlings.
I’urther experiments on siz e o f plant bands and f e r t i l i t y o f the s o il
mixtures were conducted during the spring o f 193S with s ix species;
Bromus
inerm is. Agro-pyron smith! 1. Bouteloua cnrtipendula. Bouteloua g r a c ilis . Panicum vlrgatum. and Andro-pogon furcatus.
She data on the f i r s t four species
are presented in Tables 16 to 19 as showing typical seedling growth, the
f i r s t two species representing the cool-temperature grasses, the second two
representing the warm-temperature grasses.
She e ffe c t of spotting and the
e ffe c t of d ifferen t siz e s o f bands and d ifferen t s o il mixtures upon seedling
growth were tested in the follow ing way:
Bulk seed of each of the species
was planted d irectly to h a lf f la t s of the small plant bands (^8 individual
plant bands each).
The seedlings were la te r thinned to one plant per band.
To produce comparable seedlings for spotting, additional seed was planted
in the same kind of u n sterilized s o il on the same date.
When su ffic ie n t
growth was obtained, seedlings o f each species were spotted to h a lf f la t s
of three d ifferen t siz e s o f plant bands and to h a lf f la t s of fiv e le v e ls
of fe r tility .
In the Tables 16 to 19 the treatments r ela tin g to siz e o f band and
s o i l f e r t i l i t y are arranged in the order o f decreasing to ta l nutrients
a v a ilab le.
The large bands o f s o il with only one part of manure by vol­
ume, contained more available nitrogen than medium bands or small bands
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w ith the same p rop ortion s o f s o i l and manure; sm all hands w ith two p a r ts
o f manure to f i r e o f s o i l and one o f sand fu rn ish ed more n u tr ie n ts than
hands w ith one p a rt o f manure, w ith one p a r t o f manure and one p a rt o f
sand, or w ith no manure.
A s o i l mixture o f interm ed iate f e r t i l i t y was
prepared by m ixing 10 grams o f tr e b le superphosphate to the f l a t o f s o i l
a t the time i t was f i l l e d .
In a d d itio n an a p p lic a tio n o f two and one-
h a lf grams o f ammonium sulphate p er f l a t , a p p lie d in s o lu tio n a t weekly
in t e r v a ls , was given to th is group o f s e e d lin g s .
The cool-tem perature
s p e c ie s r ec e iv ed fo u r , and the warm-temperature s p e c ie s r ec e iv ed three
weekly a p p lic a tio n s .
With the cool-tem perature g r a s s e s , the chemical fe r ­
t i l i z e r treatm ent was surpassed on ly hy the m ixture o f f i v e p a r ts s o i l ,
one p a rt sand, and two p a r ts manure, in producing growth in the sm all
hands.
These treatm ents were, th e r e fo r e , considered the r ic h e s t s o i l
m ixtu res.
The t o t a l a v a ila b le n u tr ie n ts o f the la r g e hands w ith only one
p a r t o f manure made a la r g e p la n t growth p o s s ib le , hut the medium-sized
hands apparently were n o t la r g e enough to produce a g r ea ter growth than
th a t made hy the r ic h e r m ixtu res.
The response o f the se e d lin g s o f Bromus inerm is to th ese treatm ents
was in d ir e c t prop ortion to the space and n u tr ie n t m a te r ia ls a v a ila b le
fo r growth (Table 16 and f i g . 7 ).
The s e e d lin g s produced hy p la n tin g
d ir e c t ly to the p la n t hands produced a somewhat la r g e r growth than the
sp o tte d s e e d lin g s in the same s iz e o f co n ta in er.
This was to he esp ected
sin c e the p ro cess o f s p o ttin g d ela y s growth u n t il the p la n ts can he re­
e s ta b lis h e d .
The growth in the two treatm ents was d ir e c t ly comparable sin c e
the seed in both c a se s had been s ta r te d in u n s t e r iliz e d s o i l .
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The sp o tted
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fable l 6 .—»Growth, of seedlings of Bromus inermis in the greenhouse as a ffected "by spotting, hy -toe siz e of
container, said hy the kind o f s o il mixture. Seed planted February 25» 1938* ^ u n sterilized s o i l .
?
Maximus,
* •
{plant height i / ( e a . ) ! Humber o f leaves
iDry w e i^ t
Humber o f shoots l / s o f tops SJ
:________________________:___________________
t________________________ 1 (mam.)
:Apr. 5U pr. 2Q:May 5:ipr. 5*Apr. 20iMay 5?Apr. 5*Apr. 20{May 5i May 10
Seedlings from seed planted
d ir ec tly to small bands, 5- 0-1
Seedlings spotted on March 10
Large bands, 5-0-1
Medium bands, 5-0-1
Small bands, 5-1-2
Small bands, s o il,
treble superphosphate, and
ammonium sulphate
Snail bands, 5-@-l
Small bands, 5-1-1
Small bands, straight s o i l
1/
±1{
,
1^*1
22.1
23.3
*.7
16.7
22.6
1.6
3.8
4.7
665
16.1
14.7
13.6
21.3
17.6
18.4
22.4
19.5
21.6
4.3
4.6
15.7
13.7
11.7
18.2
17.5
16.3
1 .4
1 .2
1 .0
3.7
3.3
2.3
4 .2
3 .7
3.8
497
264
312
1S.3
15.0
14. S
13.4
23.1
16.3
14.8
14. 4
24.5
17.0
l4 .0
14.1
4.7
5.1
4.5
M
12.1
10.4
7*5
7.6
15.0
13.0
10.4
3.0
1.1
1.2
1.1
1.0
3.3
2.7
1.3
1.8
3 .7
3 .1
2 .4
2.1
293
236
125
l©6
Averages obtained from the measurements o f 40 or more seedlings.
Is/ Averages obtained from the weights o f 20 seedlings.
2 / Humbers refer to parts by volume of s o i l , sand, and manure, resp ectiv ely , o f the s o il mixture in
which the seedlings were grown.
VJl
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fable 17. —Growth of seedlings of Agropyron sm ithii la the greenhouse as a ffected hy spotting, hy the siz e
o f container, and hy the kind of s o il mixture. Seed planted February 25» 193^» in u n sterilized s o i l .
treatment
Maximum
p la n t h e ig h t (cm .)
Humber o f le a v e s
lumber o f sh o o ts
SJL .
Apr. 5t£pr. 201Mar 5{Apr. <5;Apr. 20;
Apr. 5:Apr. 20: la y 5: May 10
S eed lin g s from seed p la n te d
S eed lin g s sp o tted on March 10
Large hands* 5-0-1
Medium hands, [>-0-1
Small hands, 5 -1-2
Small hands, s o i l ,
tr e b le superphosphate, and
ammonium sulphate
Small hands, 5-0-1
Small hands, 5-1-1
Small hands, str a ig h t s o i l
iSry w eight
o f top s
11.2
15.6
19.3
4.1
s.4
11 . s
1 .0
2.4
3 .2
259
13.5
IS .9
14.1
11.1
15.6
19.7
13.0
1 .0
1 .0
1 .0
2.9
11.9
4.2
4.5
4.1
9*8
15.9
2 3 .2
IS .9
4.0
3.5
3.4
36s
251
265
13.4
16.9
14.6
13 .O
13.5
17.0
4.1
4.4
4.2
3.9
7a
8.3
5.3
4.8
2 .7
2 .7
1 .6
1 .2
159
1%
108
76
12.0
12.6
12.5
12.3
15*1
15.0
14.3
g.5
11.9
8.8
8.9
6.7
4.3
1 .0
1 .0
1 .0
1 .0
2.9
2.3
2 .1
2.4
1.4
l.l
*-4
ON
77
[Fig. 7• —Representat ive seedlings of Bromus inermis produced
"by d ifferen t methods: Left to r i^ it , seed planted d ir ec tly
into a small “band; seedlings spotted into large, medium, and
small hands o f s o il and manure, into a small hand of straight
s o il, into a small hand o f f e r t iliz e d s o i l , and into small
hands o f s o il, sand, and one or two parts of manure.
Fig. 8 .—Representative seedlings of Agropyron sm ithii, produced
hy d ifferen t methods: Left to righ t, seed planted d ir ec tly
into a small hand; seedlings spotted into large, medium, and
small hands o f s o il and manure, into a small hand o f straight
s o i l , into a small hand of f e r t iliz e d s o i l , and into small
hands of s o i l , sand, and one or two parts of manure.
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seedlings in the large and medium hands made a growth which exceeded those
o f the small "bands containing the same s o il mixture,
"bands approached that made by the direct plan tin g.
The growth in the large
She average number of
shoots per plant a t the la s t counting in th is t e s t , 4 .2 , 3*7* and 3«1 shoots
for the large, medium, and small bands, resp ectiv ely , compared sim ilarly to
the r e su lts of the previous te s t recorded in Sable l 4 .
t e s t the average number o f shoots per pl ant—
In th is previous
2. 4, and 1 .7 , resp ectively,
was lower because no manure was used in the s o il mixture.
The application o f the readily available ammonium sulphate to the
seedlings of Bromus inermis produced a rapid growth, as i s shown by the
data for the maximum plant height, and to a le s s e r extent by the data on
number o f leaves.
T illerin g was also much more rapid in the ammonium sulphate
treatment than in the treatment including one part o f manure.
There i s a
tendency for the nitrogen in the manure to be tied up by b acterial action
in the early weeks.
In the chemical f e r t iliz e r treatment, the lig h t appli­
cations of ammonium sulphate had to be continued to keep the plan ts in good
condition while in the manure treatment plant growth was b etter over a longer
period.
The s o il mixture including two parts of manure produced the b est
growth in small bands.
The seedlings o f Agropyron smith! 1 behaved sim ilarly to those of Bromus
inerm is, since both species are cool-tenqperature grasses and require consider­
able nitrogen (Table 17 and Fig. 8 ).
Uhen bands o f equal siz e and mixtures
o f equal f e r t i l i t y are compared, the seedlings which had been transferred
by spotting made a slower growth than the undisturbed seed lin gs.
However,
the seedlings spotted into large bands surpassed the seedlings in the small
bands o f the d irect planting.
This i s due in part to the unevenness of
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germination and growth of the la tte r seedlings.
A greater uniformity o f
seedlings i s invariably obtained by the selectio n o f seedlings o f sim ilar
age in the spotting procedure.
The seedlings of the wheatgrass in small
bands gave best r esu lts with treatments containing the largest quantities
of manure.
She seedlings of the warm-temperature grasses which grew slowly in
early spring were spotted at a la te r date than those o f the cool-tempera­
ture grasses, and the chemical f e r t iliz e r treatment consisted o f only three
weekly app lication s.
The transferred plants were much more uniform in
growth than those planted d ir ec tly into the u n ste r iliz e d s o i l .
Here the
poor germination and lo ss of seedlings by disease gave a very uneven stand
o f p la n ts.
The gramas, however, (Tables IS and 19 and F igs. 9 and 10) made
an exceptional growth when not disturbed, producing a large number of leaves
and t i l l e r s .
The seedlings of these species responded to f e r t iliz e r and
size o f band in the same order as did the cool-temperature grasses, with
the exception of the treatments including the high-concentrations of manure.
In the small bands both Bouteloua curtioendula and B. g r a c ilis seedlings
produced more rapid and better -growth with the treatment including the appli­
cation o f the readily available ammonium sulphate than in the other treat­
ments.
The mixture of s o i l , sand, and two parts o f manure proved to be be­
yond the lim it o f nitrogen requirements and exhibited a d e fin ite ly retard­
ing e ffe c t.
Since the ammonium sulphate applications were also fewer, the
data indicate that the nitrogen requirements of the warm-temperature grasses
in the greenhouse a t th is time of year is d e fin ite ly somewhat lower than the
nitrogen requirements of the cool-teuperature grasses.
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
fable 18.—Growth o f seedlings of Bouteloua curtipendula in the greenhouse as a ffected by spotting* by
the siz e of container, and by the kind of s o il mixture. Seed planted February 25» 1938, in u n sterilized
s o il.
Maximum
:
{ plant h e i# it (©at.) : lumber o f leaves
.* ______
,
i
i
Treatment
Seedlings from seed planted
d irectly to small bands, 5-0-1
Seedlings spotted on March 17
Large bands, 5-0-1
Medium bands, 5-0-1
Snail bands, 5*1-2
Small bands, s o i l ,
treble superphosphate, and
ammonium sulphate
Small bands, 5-0-1
Small bands, 5-1-1
Small bands, str a i^ it s o il
Humber of shoots
7.5
gs
lM
k .5
19.0
32. 8
2.0
5.8
7.1
5.1
6.2
7.3
5.7
10.3
11.7
10.0
3.8
4.0
3*5
.
7.3
8.8
6.6
12.1
15.*
11.2
1.0
1.0
1.0
9.1
7.9
6.7
6.7
10.2
7.9
6 .5
13.0
12.5
10.6
7.3
!*•?
10.^
8 .9
8 .2
7.0
lM
1^.5
1^.0
10.8
1.1
1.0
1.0
1.1
sA
K i
k .2
{Dry weight
i o f tops
ia L -
8.3
276
2.1
2.6
l .S
4.0
2 .9
79
153
87
H
2,6
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3.9
3 .8
3.6
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82
Pig. 9 .—-Hepresentative seedlings of Bouteloua curtipendula produced
by d ifferen t methods: Left to r ig h t, seed planted d ir ec tly into
a small hand; seedlings spotted into large, medium, and small hands
of s o il and manure, into a sraa3.1 band o f straight s o i l , into a small
hand o f f e r t iliz e d s o i l , and into small hands of s o i l , sand, and
one or two parts of manure.
Pig. 10.---Bepresentative seedlings of Bouteloua g r a c ilis produced
hy d ifferen t methods: Left to rig h t, seed planted d irectly into
a small hand; seedlings spotted into large, medium, and small hands
of s o il and manure, into a small hand of straigh t s o i l , into a small
hand o f f e r t iliz e d s o il, and into small hands of s o i l , sand, and one
or two parts o f manure.
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The r e s u lt s o f th ese t e s t s have given ample j u s t i f i c a t i o n fo r the prac­
t i c e s which have "been developed fo r handling the germ ination and s e e d lin g
growth o f th e v a rio u s g r a ss e s.
In th ese l a t t e r t e s t s the "bulk seed used was
germ inated in u n s t e r iliz e d s o i l in order th a t the e f f e c t s o f s p o ttin g might
he determined hy comparable growth o f the s e e d lin g s ,
s e e d lin g s may he in crea sed in two ways:
The growth o f sp o tte d
F i r s t , i f seed i s germinated in
s t e r i l i z e d s o i l , stron ger se e d lin g s may he produced which, in comparison
w ith seed p la n te d d ir e c t ly to the f l a t s , do n o t s u ffe r a s g rea t reta rd a tio n
o f growth on s p o ttin g .
This method has produced s e e d lin g s which have even
surpassed the growth o f undisturbed s e e d lin g s in u n s t e r iliz e d s o i l .
Secondly,
a b e tt e r type o f s e e d lin g growth may he obtained hy in c r e a sin g the s iz e o f
the con tain er or the con cen tration o f a v a ila b le n u tr ie n ts .
Since space and
m a te r ia ls can he saved hy the use o f the sm all hands, th ese have been used
w ith an attem pt a t secu rin g the c o r r e c t f e r t i l i t y l e v e l fo r b e s t growth.
Since the stren g th o f the manure, u n le ss in continuous u s e , i s sometimes
d i f f i c u l t to gauge, i t i s b e s t to u se a somewhat too low , rath er than too
h ig h a co n cen tra tio n .
Good r esu lts have been obtained by a combination o f treatments dis­
cussed.
A s o il mixture of fiv e parts o f s o il and one part manure is used
in which to spot the seedlings.
I f their i n i t ia l growth i s too slow, one
or even two weekly applications of ammonium sulphate per f l a t gives them
a good sta r t, u n til such time as the nitrogen of the manure becomes avail­
able.
I f the manure is exceptionally rich , sand may a lso be added to the
i n i t ia l s o il mixture.
The color o f the plants and th eir rapidity of growth
can he used as a measure of whether a further application of nitrogen is
necessary.
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I f space and time permit, a more readily available nitrogen supply in
the newly spotted f l a t may he secured hy making the s o il mixture some time
in advance.
When the mixture i s moistened a fter a period in the dry con­
d itio n , considerable more b acterial a c tiv ity resu lts ( 23) . and more nitrogen
becomes availab le.
An added advantage l i e s in the sprouting of weed seeds
before the f la t s are f ille d ,
E ffects o f temperature and lig h t . —The proper control o f tenperature
i s e sse n tia l for the best seedling growth,
For the cool-temperature grasses
such as the bromegrasses and wheatgrasses, the early period o f seedling
growth should be under r ela tiv e cool temperature conditions.
between 60° and SO0 F. are desirable.
Temperatures
The greenhouse should be allowed to
warm up to the higher temperature for only a short period each day.
Pro­
longed periods o f high temperature cause an excessively t a ll growth at the
expense of t ille r in g and a dark green color in the lea v es.
Under cool tem­
peratures the s o il mixture needs to contain a source of readily available
nitrogen for these species.
The e ffe c t of supplementary lig h t i s somewhat
sim ilar to that o f high temperatures.
I t i s not considered e sse n tia l to
increase the day length by a r t i f i c i a l lig h tin g for the growth o f these
seed lin gs, but supplemental liggit on dark winter days or in corners of the
greenhouse where lig h t i s poor may be advantageous for continuous growth.
A sharp d iffe re n tia tio n is made in the handling of the warm-1emperature
grasses as compared to the cool-temperature grasses.
The gramas and blue-
sterns, for example, require much higher temperatures than the bromegrasses
and wheatgrasses.
Cessation o f growth under the midwinter greenhouse con­
d itio n s of cool temperature and short days, may be detrimental to the
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ev en tu a l estab lish m en t o f the s e e d lin g s o f th ese warm-temperature g r a ss e s.
B iis i s p a r tic u la r ly true o f the long-sea.son g rasses* li k e th e blu estem s.
With th e s e , anthocyanin pigm ents are formed under th ese c o n d itio n s as though
the p la n ts were goin g in to a p erio d o f f a l l dormancy.
Once in t h is condi­
tio n th e s e e d lin g s are slow to recover and may he l o s t b e fo r e f i e l d estab ­
lish m en t.
Ehe warm-temperature g r a sse s conseq uently cannot be moved to the
coldfram es or f i e l d u n t il danger o f f r o s t i s o v er.
S eed lin g s make good
growth in the greenhouse a t tem peratures ranging from 75°
100° F, and
t i l l e r b efore producing too t a l l a growth to handle in tr a n sp la n tin g .
R el­
a t iv e ly high tem peratures appear to be more important than l i g h t , and i t
has n o t been found e s s e n t ia l to in crea se the day len g th beyond th a t o f the
len g th en in g days o f the sp rin g months in which th ese s e e d lin g s are grown.
A len gth en in g o f the d a ily p erio d o f lig h t in g m ight be advantageous i f th ese
s e e d lin g s were grown during the short days o f w in ter.
Advantages and disadvan tages o f s p o ttin g . —Based upon the r e s u lt s o f
the fo reg o in g experim entation on germ ination and s e e d lin g growth, the prac­
t i c e has been to germ inate seed in the la r g e th ree and th r e e -fo u r th s inch
bands o f s t e r i l i z e d s o i l .
The s e e d lin g s are then sp o tted as in d iv id u a l
p la n ts to the sm aller p la n t bands o f u n s t e r iliz e d s o i l o f the proper m ixture,
a s the age o f the se e d lin g s w arrant, and as the a v a i l a b i l i t y o f lab or and
a d d itio n a l space req u ired fo r the separated s e e d lin g s p e r m its.
Certain
marked advantages and a few d isadvan tages to such p r a c tic e s should be n o ted .
With most o f the s p e c ie s , a la r g e r number o f s e e d lin g s can be secured
from m a l l seed l o t s o f seed p la n te d in s t e r i l i z e d s o i l , than i f p la n te d in
u n s t e r iliz e d s o i l .
B iis i s due to the e o n tr o l o f unfavorable fa c to r s in
the s o i l which a f f e c t seed germ ination, s e e d lin g emergence, and the i n i t i a l
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estab lish m en t o f s e e d lin g s .
The growing o f s e e d lin g s in s t e r i l i z e d s o i l
le s s e n s the p o s s i b i l i t i e s o f s e le c t io n fo r r e s is ta n c e o f s e e d lin g s to d is ­
ease*
However, stu d ie s o f oth er ch aracters than d is e a se r e s is ta n c e must
be c a rr ie d on con cu rren tly but sep arate from p a th o lo g ic a l s tu d ie s .
Seed­
l i n g d is e a s e s u n le s s found to be fa c to r s o p era tin g in the f i e l d as w e ll
as in greenhouse c u ltu r e , may be o f l e s s importance fo r in te n s iv e study.
A b e t t e r i n i t i a l s e e d lin g growth i s obtained in s t e r i l i z e d than in u n ster­
iliz e d s o il.
With sp o ttin g from a s t e r i l i z e d s o i l , a more uniform stand
and growth o f s e e d lin g s i s ob tain ed in the sm all bands than i f the seed s
were p la n ted d ir e c t ly .
Since p la n ts ifeich make a poor growth in the green­
house u s u a lly behave s im ila r ly a f t e r tr a n sp la n tin g to the f i e l d , t h is u n i­
form ity o f growth i s d e s ir a b le in the determ ination o f h e r ita b le ch a ra cters.
The immediate e f f e c t o f s p o ttin g i s the reta rd a tio n o f growth o f the
s e e d lin g fo r a sh ort p e r io d .
When vigorou s s e e d lin g s , such a s those secured
by germ ination in s t e r i l i z e d s o i l are sp o tte d , the recovery i s rapid and in
some In sta n ces growth has been produced which surpassed th a t o f s e e d lin g s
p la n te d d ir e c t ly to u n s t e r iliz e d s o i l .
A c o n tr ib u tin g cause o f good growth
i s found in the b e tte r p h y sic a l co n d itio n o f sp o tte d f l a t s than o f f l a t s o f
sm all bands in to which seed i s p la n te d d ir e c t ly .
The w atering o f the s o i l
in sm all bands during the p e r io d o f germ ination and i n i t i a l esta b lish m en t
o f the s e e d lin g may tend to compact the s o i l and g iv e i t a poor stru ctu re
aB compared to the w atering o f a f l a t in which a mass o f fib r o u s ro o ts are
soon growing.
The procedure o f s p o ttin g saves co n sid era b le time over th a t
o f p la n tin g s e v e r a l sm all seeds to each o f the sm all bands and l a t e r th in ­
n in g to s in g le p la n t s .
With s p o ttin g , stands o f sep arate in d iv id u a l p la n ts
are secured w ithout th e n e c e s s it y o f going over the f l a t s sev e r a l tim es fo r
th in n in g ou t the la t e emerging s e e d lin g s .
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The g r e a te s t advantages o f the method are those o f con servation o f space
and d is tr ib u tio n o f la b o r .
I t i s p o s s ib le to s t e r i l i z e a l l o f the s o i l n ec­
e ssa r y fo r germ ination and e a r ly estab lish m en t o f s e e d lin g s; i t would be im­
p r a c tic a b le and u n d esirab le to s t e r i l i z e a l l o f the s o i l needed fo r th e ir
growth and propagation to the f i e l d .
Seeds o f a la r g e number o f s e le c t io n s
may be germ inated in rather small space a t a fa v o ra b le tim e.
counts and s e e d lin g n o te s may be taken.
Germination
A fte r s e v e r a l weeks th e p la n ts may
be sp o tted as space can be made a v a ila b le through the removal o f breeding
p la n t s , or the moving o f o ld er se e d lin g s to the coldfram es, or to the f i e l d .
This makes p o s s ib le a maximum u t i l i z a t i o n o f space throughout the greenhouse
season .
Seeding and T ransplanting Seasons
The most f e a s ib le p erio d s o f the year fo r s e e d lin g propagation are de­
pendent upon the c h a r a c t e r is tic s o f the g r a sse s in r e la t io n to greenhouse
c o n d itio n s and to th e ir sea so n a l ad ap tation to f i e l d tr a n sp la n tin g .
Some
p e r io d s are more favorab le f o r o b ta in in g a maximum germ ination o f seed o f
a grass.
The e x is t in g greenhouse c o n d itio n s a ls o make some p erio d s more
favorab le fo r producing the d e sir e d type and r a te o f s e e d lin g growth.
The
f i e l d su r v iv a l o f tran sp lan ted p la n ts i s dependent upon sea so n a l temperature
and m oistu re.
To determ ine th ese b e s t p e r io d s an a p p ra isa l o f the m onth-to-
month seed germ ination , the r a te s o f s e e d lin g growth, and the temperature
resp on ses o f th e s e e d lin g s , must be made fo r each s p e c ie s .
The germ ination o f the cool-tem perature group o f g r a sse s i s r e l a t i v e l y
h igh throughout the c o o l months under greenhouse c o n d itio n s .
Maximum ger­
m inations are fr e q u e n tly obtained w ith th ese s p e c ie s in January and February
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as
which a llo w s a s u ita b le p e r io d fo r th e ir growth b efo re tr a n sp la n tin g e a r ly
in the spring*
Since t h is group can be moved to coldfram es and to the f i e l d
r e la t iv e l y e a r ly in r e la t io n to sp rin g f r o s t s , i t i s d e s ir a b le to s ta r t the
se a s o n 's work o f propagation w ith th ese s p e c ie s .
Some o f the slow growing
g r a ss e s may be s ta r te d f i r s t , fo llo w ed by th ose which make a more rapid
growth, so th a t the group w i l l be ready fo r tr a n sp la n tin g as soon as weather
perm its*
In p r a c t ic e , sin c e Poa p r a te n s is germ inates w ell in December i t
h as been s ta r te d f i r s t in l a t e December or e a r ly January.
The s e e d lin g s
grow slo w ly and th ree to f iv e weeks may e la p s e b efo re sp o ttin g ,
This p la n t­
in g may be fo llo w e d by p la n tin g s o f the seed o f the Agropyron s p e c ie s , Bromus
in e r m is, and o th er cool-tem perature g r a sse s during the l a t t e r p a rt o f Janu­
ary and the f i r s t h a lf o f February.
These s p e c ie s are somewhat more rapid
in e a r ly s e e d lin g growth than th o se o f Poa and may be sp o tted a t the age o f
two or three weeks a fte r seed in g .
They make a slow , stead y growth w ith the
production o f a number o f t i l l e r s b efo re the o n set o f the high maximum tem­
p e r a tu r e s o f the sp rin g months.
During a fa v o ra b le p erio d o f days in la t e
March or e a r ly A p r il, they can be moved to coldfram es and then to the f i e l d
as weather c o n d itio n s p erm it.
S eed lin g s o f the Poa s p e c ie s have been trans­
p la n te d a s e a r ly a s the l a t t e r p a r t o f March, and w ith sto o d a l i g h t f r o s t
fo llo w in g tra n sp la n tin g ; s e e d lin g s o f Bromus inerm is and D a c ty lis glom erate
have lik e w is e been tran sp lan ted e a r ly in A p r il b efo re the l a s t f r o s t , w ith
equal su c c e ss.
V a ria tio n s In the season w i l l spread the tra n sp la n tin g o f
the cool-tem perature g r a sse s throughout the month o f A p r il or even in to the
f i r s t week in May.
During dry y ea rs i t i s d e s ir a b le to move t h is group to
the f i e l d as e a r ly as p o s s ib le , in order to take advantage o f the more e f f e c ­
t iv e sp rin g p r e c ip it a t io n a t low tem peratures.
I f they become w e ll e s ta b lis h e d
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89
during t h is p e r io d they w i l l b e tt e r w ithstand the h o t , dry weather o f mid­
summer.
Another a lte r n a tiv e i s f a l l tra n sp la n tin g .
Since some o f the c o o l-
tenperature g r a sse s respond t e s t to f a l l seed in g in the f i e l d t h is appears to
he a prom ising p e r io d fo r esta b lish m en t i f m oistu re c o n d itio n s are fa v o r a b le .
Growth i s then made during two p e r io d s o f cool-tem p erature b e fo r e the p e r io d
o f the h ot summer months.
High p ercen ta g es o f su r v iv a l have been obtained
w ith Bromus Inerm is and Agronvron c r is t a turn w ith f a l l tr a n sp la n tin g under
fa v o ra b le m oisture c o n d itio n s .
Only f a i r r e s u lt s were a ch iev ed with Agro-
pyron s m ith ii under extrem ely dry f a l l c o n d itio n s.
F a ll tra n sp la n tin g i s
n o t recommended fo r D actyl i s glome r a ta fo r t h is region where se e d lin g s o f
t h is s p e c ie s w in t e r k ill.
fa ll.
Other g r a sse s have n o t been tran sp lan ted in the
Low germ ination o f seed and poor se e d lin g growth o f the cool-tem pera­
ture g r a sse s in the greenhouse during hot seasons make the p r a c tic e q u estio n ­
a b le ,
During the p erio d o f the in v e s tig a tio n m oisture has been the lim it ­
in g fa c to r in the f i e l d and an added hazard has been the accompanying a t­
tack s o f grasshoppers,
f h is n e c e s s ita te d a v ery l a t e tra n sp la n tin g near
the date o f the average f i r s t f a l l f r o s t .
fhe warm-temperature g r a sse s respond b e s t to the l a t e sp rin g trans­
p la n tin g j u s t p r io r to the p e r io d o f summer tem peratures a t which they w i l l
make th e ir maximum seasonal growth.
She order o f greenhouse s e e d lin g prop­
a gation fo llo w s a f t e r the seed in g and s p o ttin g o f the cool-tem p eratures
gra sses.
From the germ ination r e s u l t s , the two gramas, B outeloua curtipend-
u la and B. g r a c i l i s fo llo w n ex t in order in a tta in in g a high germ ination in
the monthly germ ination t r i a l s .
The seed may be expected to g iv e a good
R ep ro d u ced with p erm ission o f the copyright ow ner. Further reproduction prohibited w ithout p erm ission.
germination in February or early March.
The slow growing seedlings may be
allowed to grow for several weeks with spotting during the la t te r h a lf of
March, as space can he made available hy the removal to coldframes of some
o f the old est seedlings o f the cool-temperature grasses,
This w ill allow
su ffic ie n t time for the growth o f seedlings to he transplanted in early May.
Sim ilarly, the plantings of Buehloe dactyloides. Bouteloua h irsu ta, the
Andropogon spp., and Panleum virgatmn may he made in the la tte r h a lf of
March or the f i r s t of April for spotting as greenhouse space becomes a v a il­
able.
The seedlings of these species must not he c h ille d hy exposure to
freezing temperatures.
They make their best growth i f transplanted during
the middle or the la tte r part of May.
F ield Establishment
Several thousand grass seedlings were transplanted to the f ie ld each
o f the four years o f th is study.
Seedlings o f IS d ifferen t species have been
grown in the greenhouse for f ie ld transplanting in large enough numbers to
have determined the s u ita b ility of methods in th eir propagation.
Seedlings
of numerous other le s s common species have been grown in small numbers.
The
number o f seedlings transplanted exceeded 16,000 in 193^* 18,000 in 1937*
30,000 in 1938* and 25,000 in 1939 rising the described methods and procedures.
Since these transplanted plants are retained a minimum o f two and frequently
three years in the original planting s i t e , a large number o f plants o f d if­
ferent ages were under observation each year.
Transplanting of the seedlings o f 15 species during the spring of 193^
was done between the fourteenth o f May and the second week o f June.
Only
lig h t showers were received during the balance o f the summer and the estab-
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lishment o f seedlings daring th is year m s low due to the extreme drought
and the attacks o f grasshoppers during midsummer,
The cool-temperature grasses
were transplanted too la te in the spring to make a good growth before the
advent of hot weather and in sect attack.
One lo t o f Agropyron c r ista turn and
one of Bromus inermis were e n tire ly destroyed.
Another l o t o f Bromus inermis
survived 5U per cent; a lo t of D actylis glome rata U3 Per cent; and lo ts of
Agropyron sm ithli and 4 . pauciflorua survived 73 and 60 per cent resp ectively.
Seedlings o f some o f the warm-temperature grasses gave higher f ie ld
survivals in 1936 than those of the cool-temperature grasses.
The la te
spring transplanting was optimum for their establishment where moisture was
s t i l l available and the young seedlings were not subject to attack by grass­
hoppers as were those of the introduced sp ecies.
Attempts at watering the
plants a t the time of transplanting were not su ccessfu l.
Had stifficien t
rain followed before the s o il around the plant became hard and dry, the
plants would have extended their root systems beyond the immediate region
o f the watered s o i l .
Lacking th is uniformity of s o il moisture the plants
became stunted and as heavy lo sse s were sustained as with the unwatered
p la n ts.
Losses of seedlings were heavy prior to July and s t i l l other lo sse s
occurred during the midsummer.
Several large plantings o f the bluestems and
switehgrass survived between to and 9° per cent, depending upon the moisture
supply in their respective f ie ld s .
Bouteloua g r a c ilis survived 56 per cent;
one lo t of Buehloe daetyloldes survived Sh per cent in a dry upland f ie ld
and one transplanted in early June in a more favored f ie ld survived 90 per
cent.
With prospects of another year o f drought follow ing 193^* the transplant­
ing of seedlings was carried out ea rlie r in the spring o f 1937 than the pre-
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92
vious year.
The resu lts with fourteen species i s presented in Table 20.
The
cool-temperature grasses transplanted during the early part o f April gave
high percentages o f establishment since they made a good growth during the
cool early season itoen su ffic ie n t moisture was availab le.
The resu lts of
early transplanting o f some of the warm-temperature grasses was not so favor­
able as indicated by the survival o f d ifferen t lo t s of Andropogon furcatus.
&. scoparius. Panicum virgatum and Sorghastrum nutans.
The temperatures of
mid-April are too low for growth of these sp ecies, although Bouteloua cu rtlpendula and B. g r a c ilis did r e la tiv e ly b etter with early transplanting than
the blue stems.
The low percentage o f total survival in 1937 was largely due
to the too early transplanting of the warm-temperature group.
The b est r e su lts o f transplanting were secured during the f a l l of 1937
and the spring of 1938 (Table 2 1 ).
Over 30,000 seedlings of nine of the more
important species were transplanted at a su itab le time as related to the tem­
perature adaptation o f the sp ecies.
A high survival o f 97 per cent was secured.
The f a l l transplanting o f the cool-temperature grasses is desirable only i f
there i s a su ffic ie n t moisture supply in the s o i l .
Somewhat e a rlie r dates of
transplanting in the f a l l could be planned with more surety of success i f the
danger o f lo ss by grasshoppers was not a factor.
The seedlings transplanted
during the spring o f 193® became established with a high survival of plants
due to the e sp ecia lly favorable moisture supply of the spring months and the
cool temperatures o f May (Fig. 1 1 ).
Successful spring transplanting, i f carried out at the proper time for
each sp ecies, i s largely dependent upon the spring r a in fa ll.
This was shown
by the lower survivals of transplanted plants during the spring of 1939 with
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
fable 20.—Dates of greenhouse seeding and f i e l d transplanting as related to f ie ld .establishment
o f grass seedlings transplanted to dry-land nurseries during the spring o f 1937. 3 /
: Total
Survival
Bate
Species and
Transplanted :seedlings? Ho. i P. c t.
Sp otted
Planted
Cool-temperature Grasses
Agropyron spp. £ /
Various scources
Bromus inermis
Earners* lo ts
Cornercial lo t
Farmers* lo ts
D actylis glomerata
Commercial lo t s
Fhalaris arundinacea
Comerc ia l lo t s
Jan.
30
Eebr. k
Jan. 15
Eebr. ^
Eebr.
5
Eebr.
k
Eebr. 20
- ll
Eebr.^3
—
----1/
----U
April 10
1000
864
86
April
6
1
15
1000
9©o
175
l6*t
90
95
April 10
1000
S76
88
April 13
550
503
91
4205
3761
89
1*22
k2
70
9k
89
May
May
Group fa ta l
us©
k$k
$k
W a rtem p era tu re g ra sses
Andropogon foreatus
Sulk seed z / .
Selections zf.
Selfed lin e s
Andropogon scoparius
Bulk seed 37
Selections ~i/
Selfed lin e s
Bouteloua curtipendula
Bulk lo t 2 J
Selections 5J
Selfed lin e s
Bouteloua g r a c ilis
Bulk lo t s Irf.
Selection 2 !
Eebr. 22
k
Mar.
6
Mar.
S
Mar.
Mar.
6
Mar.
Mar.
Mar.
Mar.
Mar.
20
26
28
29
29
A p r il 2©
A p ril 22
A p ril 21
June
k
k
May
1000
1670
ll6 g
S36
1260
656
786
1119
Jan.
Mar.
Mar.
10
Eebr. 13
Mar. 29
Mar. 29
A p ril 19
May
4
May
1000
805
63
361*
621
51
36
77
Jan.
Mar.
Mar.
23
6
6
Eebr. 27
Mar. 27
Mar. 27
A p ril IS
A p ril 23
May
5
550
9j*5
101*5
k66
82k
93O
85
87
89
Jan.
Jan.
23
15
Mar. 13
Eebr. 2b
A p ril 19
l
May
1000
Hso
900
562
90
96
zl6
who
SI
yo
VM
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Table 20.—continued.
Species and
:____________________Sate__________ _________ :
Seed Source
:
P lan ted
;
Spotted
Total
;
i Transplanted {seed lin g s*
Survival
Bo.
i P .c t .
Warm-temperature Orassee
Bouteloua hirsuta
Oklahoma if/
Buehloe dactyloides
Bulk lo t 5 /
Pani cum virgatum
Balk lo t if/
Selfed lin e s
Sorghastrum nutans
Selections if/
Selfed lin e s
Jan.
23
Mar.
13
May
1
276
226
82
Jan.
13
Mar.
25
May
1
g*JO
770
93
Pebr. 9
Mar. 2©
Pebr. 27
April 10
April 15
May
k
100©
105
605
95
60
90
Mar.
Mar.
Mar. 28
April 10
April 23
May
%
560
170
3^5
131
62
77
S765
575©
66
5880
5191
S8
Group Total
IH6H5
lQf&l
75
Total Seedlings Transplanted
18850
1^7©2
7$
6
20
Seedlings o f warm-temperature grasses transplanted
before April 30
Seedlings o f warm-temperature grasses transplanted
a fter April 30
1/
Survivals determined at the end of the 1937 growing season,
2/
Included selectio n s o f 4 . c r is ta turn. A*smith! i . and 4 .naueiflorum.
2/
Seed planted d irectly to f la t s o f small bands o f u n ste riliz ed s o i l .
h/
Seed
5J
Seedobtained from nursery-grown p lan ts.
obtained from native grasslands.
V£>
4="
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
fable 21.—Summary o f the greenhouse seeding and f ie ld transplanting dates and o f the resu ltin g
f ie ld survivals o f grass seedlings transplanted from the greenhouse to the f ie ld during tire f a l l
o f 1937 and the spring o f 1932.
Species
:
i
Planted
t
Bate
Sootted
S Total }
Survival
: fransolanted :seedlings: No. ! P. c t.
Cool-temperature Grasses
Agropyron oristaturn
Agropyron sm ithii
Breams inermis
Bromus inermis
Boa pratensis
Boa spp.
Aug.
Feb.
Aug.
Feb.
Bee.
Bee.
2025
ISO
107
7125
102©
380
1929
156
106
701*1
1020
36O
95
97
99
98
100
95
5215
6185
160
2157
6270
%S6
5879
154
2130
6003
96
95
96
98
96
Total seedlings tra n sp la n ted .... 30,801}-
29,737
97
6, *37
25, *38
6, *37
10-25,*38
*37
h, *37
Aug.
Mar.
Aug.
Mar.
Jan,
Jan.
21, *37
10, *38
20, *37
1-19,*38
20, *38
20, *38
Oet. 13, *37
May 5, *38
Oct. 13, *37
ip r . 13-3©,*38
Mar. 19, *38
Mar. 19, *38
Warm-temperature Grasses
AndLropogon furcatus
Mar. 10-15,*38 Mar.
Bouteloua curtipendula Feb. 25-Mar. 5 Mar.
Feb. 25, *38 Mar.
Bouteloua g r a c ilis
Mar. 10-15, *38. Apr.
Buchloe dactyloides
Pan! com virgatum
Iter. 1-12, *38 Apr.
30-Apr.l8
17-23,*38
17, *38
1-10, *38
1-2, *38
May
May
May
May
May
19-21, *38
1-23, '38
15, *38
2k, 138
3-20, *38
vo
vn
’J ig . 11.—A 6000-plant nursery of "bromegrass (Bromus inermls) .
Seedlings transplanted during April and photographed in June,
193S.
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below normal r a in fa ll in April and May (Table 2 ).
Twenty-eight hundred seed­
lin g s of Poa nratensig transplanted during mid-April survived 98 per cent,
and 6 ,0 0 0 transplants of Bromus inerrais transplanted during the la tte r h a lf
o f April survived 86 per cent,
fifte e n hundred seedlings of Bouteloua g r a c ilis
transplanted May 2 survived 8J per cent.
The la te May transplantings of the
bluestems and gramas were much lower* with 75 per cent survival for 1600
plants o f Andronogon furcatus. and 80 per cent survival for 3000 seedlings
o f Bouteloua curtioendula.
survived 97 P®r cent.
However, 800 seedlings of Buchloe dactyloideg
A to ta l survival of 83 per cent for 25,000 seedlings
of eleven species was obtained at the end of the season.
With the hazards
of establishment under nonirrigated conditions, th is is not considered too
low a figu re.
T ia b illty o f Stored Seed
The seed lo t s with which the consecutive monthly germinations were
secured were retained for v ia b ilit y te s ts at la te r ages.
tested a t three-month intervals during 1938 and 1939*
were chosen as months of probable high germination.
Ihese lo ts were
September and March
Tests were made in
s te r iliz e d s o il in the greenhouse, the plantings being made as nearly as
possib le on the fifte e n th day o f the month.
Similar temperatures existed
as those reported during the same months of the preceding two years.
Data
secured with the 53 seed lo t s of seventeen species are presented in Table
22
.
Where more than one seed lo t was tested from the same year o f harvest,
the seed lo t s are l is t e d in Table 22 in the same order as in Tables 10 and
11 for the 1936 and 1937 seed resp ectively.
With the germination percentages
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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
T ab le 2 2 .—V ia b ilit y o f forage g r a ss seeds sto red a t room tem peratures fo r two, th r e e , sad fou r y e a r s a s compared w ith
maximum germ inations p r e v io u sly o b ta in ed . Seeds t e s t e d in s t e r i l i z e d s o i l in the greenhouse during September, 1938,
December, 1938, March, 1939, and September, 1939*____________________________________________ _______________________________
:
s
Species
Agropyron cristatum
Agropyron cristatum
Agropyron sm ithii
llymus canadensis
Bromus inermis
D aetylis glomerata
Poa pratensis
Poa pratensis
Hxalaris arundinacea
Bouteloua curtipendula
Bouteloua g r a c ilis
Bouteloua g r a c ilis
Bouteloua h irsu ta
Buchloe dactyloides
Andropogon fureatus
Andropogon fureatus
Andropogon scoparius
Sor^iastrum nutans
Sorghastrum nutans
Psnicum virgattra
Panicum virgatum
Sporobolus airoides
Sporobolus airoides
Sporobolus cryptandrus
Seed lo ts harvested
in 1937
Previous : Germination during
maximum s seeond year 1938-39
.germina- :
:
:
:
tiow
. Sept. .Dec* .Mar. . Sept.
P .c t.
sP .ct. :P .c t:P .c tiP .e t.
96 Feb.
95 Nov.
92 Nov.
96 Mar.
9** Oct.
95 Nov.
85 Nov.
76 Feb.
88 Oct.
77 Mar.
77 Apr.
38 84
37 71
37 79
38 24
37 80
37 72
37 57
38 52
37 83
3s 3^
38 4©
93
84
81
34
93
90
86
75
87
27
55
87
80
86
34
90
85
78
81
94
37
46
69
55
81
9
S3
63
78
18
69
20
37
58
46
58
43
38
38 23
38 30
38 21
38 l k
38 62
38 56
38 70
38 83
38 28
23
32
39
17
18
30
27
21
28
1
44
38
25
10
22
72
77
71
84
40
38
21
70 Apr. 38
77 Apr.
43 Feb.
*♦§ Mar.
46 Aug.
35 Neb.
33 Apr.
41 Anr.
81 Apr.
91 Apr.
34 Apr.
* Seed aot tested during f i r s t year.
15
12
62
57
56
69
8
Seed lo ts harvested
in 1936
Previous : Germination taring
maximum : third year 1938-39
germina- :
:
:
:
tion
.Sept. .Dec. .Mar. .Sept.
P .c t.
sP .c t.s P .c t:P .c tsP .c t.
Seed lo t s harvested
in 1935
Previous : Germination during
maximum : fourth year 1938-39
germina— :
:
:
:
tion* j Sept. .Dec. .Mar.. Sept.
P .c t.
:P .ct. :P .e t:F .c t:P .e t.
94 Oct. »36
58
53
53
11
f 6 Oct. *36 19
38
18
4
89 Aug.*37
58
53
52
15
90 Oct. *36 39
47
54
27
93 Jan.*37 75
91 Oct. *36 79
39* Feb.* 38 16
76
80
25
74
81
21
&
46
92 J a n .*37
75 Jan .*37
66
8
78
16
83
12
59
4
69
10
6
16
17
39
12
13
75
5
7
9
21
7|
17
0
0
1
17
60
33
7
1
70 Mar.*17
81 June*37 52
94 Mar. *37 37
45
.5
7
31
25
0
33
9
45 Aug. *37 12
6l June*17 45
63 Sept. *37 7
?63
12
61
65
8
47
29
3
54 Sept. ‘36 10
60 S ep t.*3® 6
20
14
19
32
16
©
97 July *37
92 June*37
94 Mar.*37
74*Nov.*37
46 Mar. *38
<58 May *17
56 Mar.*37
4l*Apr.»3S
4o
45
3
5
9
22
33
30
6
16
45
74 Sept. *37 72
4l
75
32
56 May *37
37
36
47
36
89 A pr.'38 85
32
81
64
93 May *37
81
37
79
72
8
64
18
20 June*37
20
0
27
0
62 Apr. *38
43
secured in 1938 and 1939 the maximum germination previously secured with each
o f tiie seed lo t s i s given for comparison, although th is i s o f le s s value for
the 1935 seed and a few lo t s o f 1936 seed not tested in th eir f i r s t year.
The month in which the highest germination occurred i s also lis t e d ,
fhen
the germination reached the same high percentage in more than one month the
month reported was arb itra rily chosen as representative.
By comparing the
germination o f the several lo t s during their second, third, or fourth year
a fter harvest with the highest germination previously obtained for the seed
l o t , the r ela tiv e v ia b ility of the seed at that age can be ascertained and
the probable period o f highest germination for seed of the species can be
no ted.
Most o f the cool-temperature grasses (grasses o f the f i r s t two groups,
Table 22) attained th eir highest germination under the cool greenhouse con­
d itio n s o f f a l l , winter, and early spring o f their f i r s t year and lo s t their
v ia b ilit y rapidly a fte r their third year of room-temperature storage.
exceptions occurred.
A few
The 193^ seed lo t of Agropyron sm lthli gave i t s highest
germination in August a l i t t l e over a year after harvest.
The 1935 and 1937
seed lo t s o f Fhalarls arundinacea attained their highest germination in March
and the 1936 lo t in July, of their second year.
The v ia b ility of Agropyron
cristatum and 4 . sm lthli were sim ilar in their third year but the 1935 seed
lo t of 4* cristatum lo s t v ia b ility more rapidly in i t s fourth year than did
the 1935 lo t o f 4 , sm lth li.
Pour-year-old seed of Dactyl is glomerata and
P. arundinacea gave a poor emergence and growth of seed lin gs.
The seed of
Bromus inermls gave the best germination o f any of the species of th is group
during i t s fourth year o f storage.
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100
Of the warm-temperature grasses (the grasses of the third, fourth, and
f i f t h groups, Table 22),
the 193^ and.1937 seed lo t s of the two gramas,
Bouteloua curtipendula and Bouteloua g r a c ilis , gave their highest germination
in
toe spring and summer follow ing harvest.
The 1935 seed lo t s
not tested
in
their f i r s t year gave equally high germination in the spring and summer
o f their second year, and retained their v ia b ilit y well into the fourth year*
The two lo t s o f B. g r a c ilis and toe one lo t o f 3. curtipendula harvested in
1936 l o s t v ia b ilit y in their third year.
The conditions o f harvest o f the
year 193& or the conditions follow ing harvest a t Lincoln, lebraska, where
these lo t s were grown, appeared to be unfavorable to the retention of v i­
a b ility of these sp ecies.
The periodic low germination in early winter
exhibited by previous te s ts was not repeated with the December te s t of the
four-year-old seed of these two sp ecies, which remained r e la tiv e ly high.
The 1937 seed lo t of B. g r a c ilis also gave a higher germination in December
than in the previous September planting.
The seed o f Bouteloua h lrsu ta harvested in 1935
long period o f ripening before giving a high germination.
1936 required a
These seed lo t s
were apparently l i t t l e affected by toe changes in storage temperature but
gradually increased in germination, reaching a high point during toe spring
and summer o f th eir second year.
The 1935 seed l o t gave 6 l per cent germina­
tion in March o f i t s fourth year a fter harvest, as i t s highest germination.
The 1937 harvested seed gave a high germination o f fO per cent in toe spring
o f i t s f i r s t year, sim ilar to toe high germinations o f toe other two gramas.
Seed o f Buchloe dactyloides gave sim ilar data to that of B. hlrsu ta.
The
1936 seed ripened slowly to give a high germination o f 58 per cent in May,
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101
1937*
the 1935 seed gave i t s highest germination, o f 65 Per cent in March,
193S in i t s fourth year.
She seed of these two species with th eir high degree
o f dormancy retained their v ia b ility the b est among the species of th is group.
The Andropogon species gave a somewhat lower germination than the Bout­
eloua species with most o f the seed lo t s , the highest points being reached
sim ilarly in the spring of the year after harvest.
Severe lo sse s in via­
b i l i t y as judged by emergence of seedlings from s te r iliz e d s o i l , occurred
in the third and fourth year a fte r harvest.
The second lo t of l$ j6 seed of
Andropogon fureatus harvested a t Lincoln, Nebraska gave a low germination
sim ilar to that o f the three 193& lo t s of seed of the gramas which were also
reported low in v ia b ility in their third year.
The low germination o f 12
per cent for the f i r s t 193& lo t of Andropogon fureatus in September was in­
creased to hj per cent in December.
This reversal o f periodic low and high
germination as related to season appears to be associated with the aging of
the seed l o t .
Seed of -fpdro-pogon scoparius which was rather small for the
sp ecies, also lo s t v ia b ility rapidly.
In the other two species of the bluestem—switchgrass group, the dor­
mancy previously discussed d isgu ises the true v ia b ility of the seed as
tested .
Favorable periods e x is t for high germinations under greenhouse
conditions.
Sorghastrum nutans gave 60 per cent as i t s highest germina­
tion under these conditions as compared to a maximum of 65 per cent obtained
a fte r c h illin g for four weeks.
as high
Paaicmn virgatum reached a percentage nearly
some period in the te s ts as i t did a fte r the treatments used to
break dormancy.
The 1936 seed lo t gave 75 Per cent in March of i t s third
year as i t s highest germination.
This species retained i t s v ia b ility into
i t s fourth year the best of any o f the group.
A ll o f the seed lo ts gave
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102
a c o n s is t e n tly h ig h germ ination in spring and f a l l , and a low germ ination
in December.
The 1936 and 1937 seed l o t s o f the dropseeds gave h igh germ inations in
A p r il, I93S in t h e ir second and f i r s t year r e s p e c t iv e ly .
©ie germ inations
p r e v io u s ly ob tain ed were exceeded in March, 1939 for both the 1936 and 1935
seed l o t s in t h e ir th ir d and fo u rth y ea rs r e s p e c tiv e ly .
Both Sporobolus
a ir o id e s and Sporobolus cryptandrus showed p e r io d ic dormancy w ith h ig h e st
germ ination in the sp rin g, and low germ inations in e a r ly w in ter.
a ir o id e s gave h igh germ inations a ls o in the f a l l .
Sporobolus
Because o f th e ir p e r io d ic
dormancy th ese s p e c ie s r e ta in e d th e ir v i a b i l i t y a t a high l e v e l in to the
fou rth y e a r.
Crocker (9 ) has summarized the th e o r ie s th a t have been o ffe r e d to ex­
p la in the degeneration o f seeds w ith age.
A ccording to h i s summary, ex p eri­
mental evidence to date in d ic a te s th a t the f a l l in v i t a l i t y o f seeds in dry
sto ra g e i s due to the gradual degeneration o f the n u c le i o f the embryo, thus
a f f e c t in g raeiotic d iv is io n .
This i s borne out by the s im i l a r i t i e s in seed
d egen eration caused by a g in g , h e a tin g , or X-ray treatm ents by which chro­
mosome ir r e g u l a r it ie s in the embryo a id mutant se e d lin g s are produced.
She most important storage factors operating to determine the l i f e
span of seeds are moisture content, oxygen supply, temperature, and sealed
storage (a ffec tin g oxygen supply or moisture content) as given by Crocker
(9)*
Barton has demonstrated the e ffe c ts o f controlled tenperature and
sealed storage in retaining the v ia b ility o f seeds which ordinarily have
a short l i f e spaa (H); and in la te r studies she demonstrated the e ffe c ts
of these two factors in retaining v ia b ility of sh ort-lived seeds stored
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at d ifferen t moisture contents (5)»
With room-temperature storage some of
the germination resu lts presented in th is ‘b u lletin show nearly complete lo s s
o f v it a lit y of some seeds in four years.
Although these lo t s were taken in
many instances from large hulk l o t s , they were purposely stored under ordinary
conditions as small lo t s of selectio n s o f seed are usually stored.
I t appears
possib le that i f the glumes were not removed, or i f the seed were stored in
larger lo t s under better moisture and temperature conditions for the indi­
vidual seed, that v ia b ility could be retained for much longer periods.
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104
SUMMARY
Method s tu d ie s were conducted on the problems in v o lv ed in the growing
o f g r a ss s e e d lin g s in the greenhouse fo r tra n sp la n tin g to the f ie ld *
The
development o f methods o f greenhouse cu ltu re fo r the propagation o f grass
s e e d lin g s in v o lv e s the determ ination o f procedures f o r secu rin g maximum
seed germ ination and i n i t i a l s e e d lin g esta b lish m en t from sm all amounts o f
seed and fo r o b ta in in g a s u ita b le growth o f s e e d lin g s fo r tra n sp la n tin g
to the f i e l d a t a favorab le time fo r s u r v iv a l.
The stu d ie s were conducted w ith IS s p e c ie s o f g r a sse s o ffe r in g prom ise
fo r s e le c tio n and improvement fo r u se in the e a ster n p a r t o f the Central
Great P la in s .
These g r a sse s were c l a s s i f i e d in to two g en era l groups as to
th e ir r ea c tio n to temperature and season fo r b e s t s e e d lin g growth in the
greenhouse and fo r tr a n sp la n tin g to the f i e l d .
The cool-tem perature group
in clu d ed introduced s p e c ie s such as Agropyron cristatu m and Bromus inerm is
and the n a tiv e s p e c ie s , Agropyron s m it h ii. A. p&uciflorum and Elymus cana­
d e n s is .
The warm-tauperature group was made up e n t ir e ly o f n a tiv e g r a sse s
in c lu d in g s p e c ie s o f Andropogon. B outeloua, Panicum. and Sporobolus.
Methods o f growing se e d lin g s in s o i l f l a t s o f a s p h a lt - f e lt paper bands
were developed to f a c i l i t a t e the handling o f la r g e numbers o f in d iv id u a l
se e d lin g s in the greenhouse and in moving them to the f i e l d .
were germ inated in s te a m -s te r iliz e d s o i l .
Grass seeds
The se e d lin g s a f t e r a tta in in g
the d e sir e d age were moved to f l a t s con tain in g sm all bands o f u n s t e r iliz e d
s o i l in which the s e e d lin g s were then grown fo r p e r io d s o f two to four months
b efo re b ein g tran sp lan ted to the f i e l d ,
fo r the tr a n sp la n tin g o f grass seed­
lin g s these bands were very e f f e c t i v e in r e ta in in g m oist s o i l about the
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105
fibrous roots during transplanting.
Their use m s esp ecia lly advantageous
for transplanting to nonirrigated lands in dry years.
(Termination te s ts showed increased emergence and establishment o f seed­
lin g s , and better seedling growth in steam -sterilized s o il than in unsteri­
liz e d s o i l .
Greater increases in emergence and establishment of seedlings
in s te r iliz e d s o il were secured with the grasses o f the warm-temperature
group than with those of the cool-temperature group.
Germination te s ts were conducted in s te r iliz e d s o il in each o f 25 con­
secutive months beginning in the f a l l of 193&* with seed lo t s o f the IS grasses
from the 1935* 1936*
la te r from the 1937 harvests.
These te s ts were to
determine the period o f maximum germination for securing seedlings from small
seed lo t s , and to evaluate the problems o f seed dormancy and longevity under
room-temperature storage conditions.
During 1938-1939 four additional te s ts
were run to determine v ia b ility of 53 of the same seed lo t s in their second,
third, and fourth years o f storage.
The cool-temperature grasses gave good seed germination a t most any time
o f the year that greenhouse temperatures were not excessively hi^b.
Most of
these grasses gave high seed germinations within a few months a fte r harvest
with only a few tendencies for delayed germination of the major portion o f
the seed.
Seeds of the warm-tenperature grasses exhibited greater tendencies for
dormancy than seeds o f the cool-temperature grasses.
Both primary dormancy
and seasonal secondary dormancy were found in the seeds of many of these
sp ecies.
A fter-ripening occurred in the seeds of some of these grasses in
time to secure r e la tiv e ly high germinations during the spring months with
seed of the previous year’s harvest.
These increases in germination occurred
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io6
under the greenhouse conditions of lengthening spring days and increasing
temperatures.
Seeds of other grasses o f th is group required long periods
o f after-ripenin g to reach a maximum germination.
Seed dormancy o f three
species was "broken hy special methods.
Seed lo ts o f grass seeds varied in v ia b ility due to seasonal condi­
tions o f harvest, seed ripening, and seed storage.
Loss of v ia b ility with
the seed lo t s of some species occurred rapidly a fter the second year of
storage"at ordinary room temperatures.
storage conditions should be sought.
For these grass seeds, improved
Seeds o f other grasses retained v ia ­
b i l i t y w ell.
She use o f d ifferen t siz e s of a sp h a lt-fe lt paper bands as containers
in s o il f la t s for germinating small seed lo t s and for growing individual
seedlings has been esp ecia lly conservative of greenhouse space.
By trans­
ferring the vigorous seedlings secured in s te r iliz e d s o il to the proper s o il
mixture, a good seedling growth can be obtained with l i t t l e delay due to the
transfer.
The f e r t i l i t y of the s o il mixture i s more important than the size of
the container, making i t possib le to use a r e la tiv e ly small band for individ­
ual seedlings i f deep enough for root growth to set the transplant into moist
s o il in the f ie ld .
A s o il of good structure secured by the incorporation o f
some form of organic material in the mixture and by proper uniform packing
in the f l a t , is an aid to good growth,
drass seedlings require a readily
available and continuous supply o f nitrogen.
To newly-made u n sterilized s o il
mixtures, the addition of nitrogen f e r t iliz e r in solution i s frequently o f
b en efit u n til nitrogen becomes available by normal s o il processes in the
f e r t i le mixture.
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107
Seedlings o f the cool-temperature grasses gave the "best growth in the
greenhouse in la te winter and early spring.
The r e la tiv e ly cool temperatures
of th is period produced vigorous seedlings with several t i l l e r s .
High tem­
peratures and supplementary lig h t caused a too rapid growth resu ltin g in t a ll
seedlings with few leaves and t i l l e r s .
Seedlings for spring transplanting
may he moved to coldframes for hardening and then to the f ie ld early in the
spring,
They should he transplanted to the fie ld at such a time that a
maximum of growth can he attained before the advent o f hot, dry weather and
the p ossib le attacks o f in sects and diseases.
P a ll transplanting is also
p o ssib le with th is group of grasses.
Seedlings of the warm-temperature grasses grew slowly during cool green­
house seasons,
They made their best growth during the spring months with
high d aily maximum temperatures.
Cessation o f growth caused by c h illin g of
these seedlings i s very detrimental to their establishment.
The best sur­
v iv a l o f these seedlings occurred when transplanted to the f ie ld in the
spring after a l l danger of fr o st was past.
By determining the most fea sib le order o f handling as determined by
experimental data, a plan was formulated for the production o f successive
crops of grass seedlings in the greenhouse.
For spring transplanting, seed­
lin g s o f the cool-temperature grasses are grown f i r s t , followed by those of
the warm-temperature grasses.
This accomplishes a d ivision of labor and max­
imum u tiliz a tio n o f greenhouse space.
The p ractice also conforms to success
in the f ie ld in relation to the temperature relation sh ip s of the p lan ts.
Records o f seedling survival were kept on 90 >000 seedlings transplanted
to the fie ld during the four years of th is study.
These plants were used
as te s ts of seed sources, as progeny te s ts of superior p la n ts, and for
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farther selectio n o f desirable breeding stock.
She best r e su lts in the sur­
vival of transplants were secured when attention was given to securing a good
seedling growth in the greenhouse at such a time that the seedlings could be
moved to the fie ld at the proper time for transplanting.
When th is care was
combined with reasonably favorable conditions of s o il moisture in the f ie ld ,
high percentages o f establishment were obtained.
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109
LIQ2MTURE 01TED
1.
Albertson, p. W.
1937. Ecology of the mixed p rairie in west central Kansas.
ic a l Monographs 7 s 481-547, i l l u s .
Ecolog­
2.
Anderson, A. M.
1933* The e ffe c t of carbon dioxide and some other gases on the ger­
mination of seeds o f Poa compressa. (ab stract). Amer. Jour.
Bot, 20; 67S-679.
3.
Atwood, W. M.
1914. A ph ysiological study of the germination of Avena fatua.
Gaz. 57; 3g6-4l4.
4.
Barton, Lela V.
1932. E ffect o f storage on the v i t a li t y o f delphinium seeds.
Boyce Thompson In st. 4: 14-1-153.
Bot.
Cont.
5.
__________________
6.
Blake, A. K.
1935. V ia b ility and germination of seeds and early l i f e history of
p rairie p lan ts. Ecological Monographs 5! 405-460,
7.
Crider, P. J . , and Hoover, M. M.
1937* Collection of native grass seed in the Great P lains, U. S. A.
Imp. Bur. of Plant Genetics; Herbage Plants—Herbage Publica­
tion s Series B u ll. 24-, 15 p p ., i l l u s .
8.
Crocker, Wm.
1916. Mechanics of dormancy in seeds.
9.
1939«
Storage of some flower seeds.
399-427.
____________
1938. L ife span o f seeds.
Cont. Boyce Thompson In st. 10;
Amer. Jour. Bot. 3s 99-120.
Bot. Hev. 4, no. 5, pp. 235-274.
10.
Davis, W. E.
1936. Primary dormancy, after-ripening, and the development of sec­
ondary dormancy in the embryos o f Ambrosia tr ifid a . Amer.
Jour. Bot. 17; 58- 76.
11.
P u lts, Jess L.
1936» Blue grama grass for erosion control and range reseeding in
the Great Plains and a method of obtaining seed in large l o t s .
TJ. S. Dept, Agr. Circ. 402, 8 pp., i ll u s .
R ep ro d u ced with p erm ission o f the copyright ow ner. Further reproduction prohibited w ithout p erm ission.
110
12.
Harrington, 0. T.
1923. Forcing the germination o f fresh ly harvested wheat and other
cerea ls. Jour. Agr. Res. 23 J 79-100.
13.
Hitchcock:, A. S*
1935. Manual o f the grasses of the Ohited S tates.
Misc. Pub. Ho 200.
l*t.
H orsfall, James G.
1935. Combating damping-off.
Ho. 683. **6 pp.
U. S. Dept. Agr.
Hew York State Agr. Expt. Sta. B u ll.
15.
Hoover, M. M.
1939* Hative and adapted grasses for conservation of s o il and mois­
ture in the Great P lains and western s ta te s. U. S. Dept.
Agr. Farm. B u ll. Ho. 1812.
16.
Kadow, K. J . , and Anderson, H. W.
1937* Damping-off control: An evaluation o f seed and s o il treat­
ments. 111. Agr. Expt. Sta. B u ll. *09.
1-7.
Kirk, L* E.
1933* ©ie progeny te s t and methods of breeding appropriate to
certain species o f crop p lan ts. Amer. Hat. 67: 515-531*
IS.
Robertson, J. H.
1939* A quantitative study of true p rairie vegetation after three
years o f extreme drought. Ecological Monographs Si *01-*02.
19»
Savage, D. A.
1939* Grass culture and range improvement in 'Hie central and south­
ern Great P lain s. U. S. Dept. Agr. Girc. Ho. *01. 5^ PP*
illu s .
20.
Shull, C. A.
191^. She role of oxygen in germination,
21.
22.
23.
Bot. Gaz. 57 ’• 6*1-69.
Toole, E. H.
1936. Physiological problems involved in seed dormancy.
Seed Testing Assoc. 8: 33-**!*
Proc. In t.
Toole, Vivian K.
19*10. The germination o f seed of Oryzopsis hymenoides.
Soc. Agron. 32: 33-**l.
Jour. Amer.
Waksman, S. A.
1932* P rinciples of s o il microbiology,
and Wilkins Co.
pp. 726-7*10: 758.
R ep ro d u ced with p erm ission o f the copyright ow ner. Further reproduction prohibited w ithout p erm ission.
Williams
I ll
2b.
25.
26.
Waksman, S. A .» and Starkey, S . L.
lS2h. P artial s te r iliz a tio n of s o i l , m icrobiological a c t iv it ie s ,
and s o il f e r t i l i t y . Soil Sci. 16: I 37- I 56; 21*7-268; 3^3-357.
1931*
The s o il and the microbe,
pp. 22^-229.
John Wiley and Sons.
lea v er, J. E . , and Albertson, P . W.
1939» E ffects of the great drought on the p r a iries of Iowa, Nebr­
aska, and Kansas. Ecology 17: 5^7-^39.
27. '__________________________________ _
1939* Major
M a jo r changes in grassland as a resu lt o f continued drought.
Bot. Gaz. 100: 57b-591» i ll u s .
28.
Weaver, J. E ., and Clements, F. E.
1933» Plant Ecology, pp. 132-lhO.
McGraw H ill Book Co.
29.
Weaver, J . E ., and Fitzpatrick, f . J.
193^. She p r a irie. Ecological Monographs h: 109-295» i l l u s .
30.
Weaver, J. E ., Stoddart, L. A ., and N o ll, Win.
1935* Response of the p rairie to the great drought of 193^*
Ecology 16: 612- 629.
31.
Werner, H. 0.
1931* The e ffe c t of maturity and ethylene chlorhydrin seed treat­
ment on the dormancy o f friumph potatoes. Nebr. Agr. Res.
B u ll. 57. 39 PP.
R ep ro d u ced with p erm ission o f the copyright ow ner. Further reproduction prohibited w ithout p erm ission.
100
DEGREES
90
70
60
50
s
o
1936
n
d
j
f
m
a
m
j
j
a
s
o
n
d
j
f
193 7
m
a
m
j
j
a
s
1938
GERMINATION
_
FIG. 12 - AVERAGE DAILY MAXIMUM, MINIMUM, & MEAN GREENHOUSE
TEMPERATURES PERTAINING TO THE MONTHLY GERMINATION PERIODS
90
tP -
80
70
CENT
50
PER
60
40
1936
1938
1937
FIG.
13 - GERMINATION
LEGEND
OF
BROMUS
FOR GERMINATION
F I G U R E S 13 T O 2 7
STERILIZED SOIL T E S T S
Un t r e a t e d
r e f r ig e r a t e d
SE E D
SEED
INERMIS
GRAPHS
UNSTERILIZED
s o il
tests
BLOTTER
TESTS
1935 SEED LOT
•
1936 SEED LOT
0
1937 SEED L O T ------------
O
R ep ro d u ced with p erm ission o f the copyright ow ner. Further reproduction prohibited w ithout p erm ission.
.
I 00
90
BO
GERMI
0 70
50
CENT
30
PER
40
20
1936
1937
OF AGROPYRON
CRISTATUM
_
FIG. 14 - GERMINATION
1938
90
GERMINATION
00
70
60
50
PER
CENT
40
30
20
1936
1937
FIG. 15 - GERMINATION
1938
OF AGROPYRON
SMITHII
R ep ro d u ced with p erm ission o f the copyright ow ner. Further reproduction prohibited w ithout p erm ission.
100
00
O'
GERMINATION
SO
70
60
50
PER
CENT
40
30
20
1936
1937
_
FIG.
16 -
GERMINATION
OF
DACTYLIS
GLOMERATA
oo
90
GERMI NATI ON
60
\
70
60
50
PER
CENT
40
30
20
1936
1937
FIG. 17 -
1936
GERMINATION
OF PHALARIS
ARUNDINACEA
R ep ro d u ced with p erm ission o f the copyright ow ner. Further reproduction prohibited w ithout p erm ission.
100
-
90
GERMINATION
BO
70
50
PER
CENT
40
30
20
1937
1936
18
-
GERMINATION
OF
BOUTELOUA
CURTIPENDULA
_
FIG.
1938
o
o
\N .
\
X
/
o
r
\
/
\
N.
V
t
----- r ■
O
•V -— \
.—
\
•
/
>
♦
CENT
GERMI NATI ON
/ w ’/
o
\
i
o
i
S O
1936
1 ‘
i , __ i__ i__ __ 1__ L _ — 1— 1— . ■ 1. 1__
N
O
J
F M
A M
J
J
A
S
1937
FIG. 1 9 - GERMINATION
O
N
O
J
P
M
1
«
A
M
J
1938
OF
BOUTELOUA
GRACILIS
R ep ro d u ced with p erm ission o f the copyright ow ner. Further reproduction prohibited w ithout p erm ission.
J
A S
I 00
90
GERMINATION
80
70
/ \
50
PER
CENT
40
30
20
1936
1938
1937
_
FIG. 2 0 - GERMINATION
OF
BOUTELOUA
HIRSUTA
oo
90
GERMI NATI ON
80
70
60
V
PER
CENT
40
30
20
1936
1937
FIG. 21 - GERMINATION
OF
BUCHLOE
DACTYLOIDES
R ep ro d u ced with p erm ission o f the copyright ow ner. Further reproduction prohibited w ithout p erm ission.
I 00
90
GERMINATION
BO
70
60
50
°\
PER
CENT
40
OB
30
20
1936
1937
OF ANDROPOGON
FURCATUS
_
F I G . 2 2 - GERMINATION
1936
90
GERMI NATI ON
80
70
60
50
-
PER
CENT
40
/o \/
30
20
1936
1937
FIG. 2 3 -GERMINATION
1938
OF ANDROPOGON
SCOPARIUS
R ep ro d u ced with p erm ission o f the copyright ow ner. Further reproduction prohibited w ithout p erm ission.
100
90
GERMINATION
80
70
60
50
PER
CENT
40
30
20
1936
1937
_
F I G . 2 4 -GERMINATION
1936
OF
SORGHASTRUM
NUTANS
00
90
GERMI NATI ON
80
70
60
50
PER
CENT
40
30
20
-G -1936
1937
FIG. 2 5 -GERMINATION
1938
OF
PANICUM
VIRGATUM
R ep ro d u ced with p erm ission o f the copyright ow ner. Further reproduction prohibited w ithout p erm ission.
I 00
90
GERMINATION
BO
70
60
©-
50
PER
CENT
40
30
20
1936
1937
OF
SPOROBOLUS
AIROIDES
_
FIG. 2 6 - GERMINATION
1938
90
GERMI NATI ON
80
70
60
PER
CENT
40
30
20
o-
1938
FIG. $ 7 -GERMINATION
OF
SPOROBOLUS
CRYPTANDRUS
R ep ro d u ced with p erm ission o f the copyright ow ner. Further reproduction prohibited w ithout p erm ission.
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