SIMAZINE PERSISTENCE IN SOIL AND EF}'ECTS OF ITS RESIDUE ON CROPS M. T. H. RAGAB Researclt Station, Agrictilture Canada, Kentville, Nova Scotia BlN Il5. Corttribtttion tto. 1508, received 7 Marclt 1974, accepted j lttly 1974. Can. J. Plant Sci. Downloaded from www.nrcresearchpress.com by 22.214.171.124 on 10/26/17 For personal use only. Rlcls, M. T. H. 1974. Simazine on crops. Can. J. Plant Sci. 54: persistence 713-716. in soil and effects of its lesidue When 4.48 kg,zha of simazine (2-chloro-4,6-bis(ethylamino)-s-triazine) was rncorporated with soil to a depth of 15 cm, 53, 40 and lSVo was detected at 18, 63, and 161 days, respectively, following which there was a gradual decrease to 1.5% at 69O days. When crops were grown the year after application and the soil contained 0.18 ppm simazine, no residue was detected in coln (Zea mays L.), oats (Avena sativa L.) or beans (Pltaseoltts vtrlgaris L.), but the latter two crops were injured and Swiss chard (Beta vtilgaris var. cicla L.) did not grow. There was slight toxicity to oats planted 2 yr after application when the soil contained 0.03 ppm simazine. L'incorporation de 4.48 kg,zha de simazine (chloro-2 bis-6thylamino-4, 6 triazine-s) ir une profondeur de 15 cm dans le sol, a laiss6 53, 40 ef 18% de r6sidus b 18, 63 et 161 jours respectivement, aprds quoi il s'est produit une baisse graduelle jusqu'i 1.5Vo d 690 jours. Sur cultures 6tablies un an aprds I'application, en sol contenant 0.18 ppm de simazine, on n'a d6cel6 aucun r6sidu de cet herbicide dans le mais (Zea mays L.), I'avoine (Avenu sativaL.) ou les haricots (Plnseolus vu[garis L.), mais ces deux dernidres cultures ont 6t6 endommag6e,s et la bette i carde (Beta vulgaris var. cicla L.) n'a pas pouss6. Le produit s'est r6v6l6 faiblement toxique )r I'avoine sem6e deux ans aprds I'application, en sol contenant 0.03 ppm de simazine. (Harlow and Whiteside 1943). The land Simazine (2-cbloro-4,6-bis(ethylamino)-s-tri- to simazine application. Chemical analysis orr extracts from this untreated soil showed that no simazine residue or any other pesticide residue was present prior to treatment. The plots were 5 y 7 m with l-m sod strips separating them, and were arranged at random in four times injures crops that follow in the crop- ping system. Reduction in yield of oats (Avena sativa L.), wheat (Triticum aestivum L.), soybeans (Glycina nmx Merr.), several small seeded grasses, and legume forage species have been reported for simazine carryover (Roadhouse and Birk 1961; Fink and Fletchall 1963, 1969; Holly and Roberts blocks. On 10 June 1968 commercially formulated simazine 50W was applied by a power sprayer over the surface of the soil at a rate of 4.48 kg 1963; Talbert and Fletchall 1964). The present study was, therefore, initiated to obtain information on the long-term persistence of simazine when incorporated in the soil under the environmental field conditions of Nova Scotia. The simazine carryov€r elTects on some agricultural crops were also investigated. MATERIALS AND METHODS The experimental site was at Canard, Nova Scotia on soil classified as Somerset sandy loam Can. J. Plant Sci, 54: 713-716 (Oct, 1974) had been fallowed and was cultivated just previous azine) has been extensively used for control of weeds, but its carryover in the soil some- (a.i.) /ha in I,075 liters of water and immediately incorporated into the soil to a depth of approximately 15 cm by a rotary cultivator. Apart from the simazine treatment there was no other control of weeds except that the untreated check plots were always kept mechanically weeded. No pesticide treatment of any type was applied to plots throughout the ex- perimental years. Soi[ samples were randomly taken during the 1968, 1969 and 1970 growing seasons on the dates given in Table 1 from each plot at 0- to 15-cm depth with a soil sample 2.5 cm diam. Each soil sample was thoroughly mixed and stored frozen in a carton until analvsis for 713 7t4 CANADIAN JOURNAL OF PLANT SCIENCE Table I Date sampled . Simazine in the top l5 cm of soilt Days after application Can. J. Plant Sci. Downloaded from www.nrcresearchpress.com by 126.96.36.199 on 10/26/17 For personal use only. 28 June 1968 l2 Aug. 1968 18 Nov. 1968 l3 May 1969 27 Nov. 1969 I May 1970 30 Sept. 1970 Precipitation// Simazinel between sampling content (ppml (cml I .06+0.11 0.80 + 0.08 12.1 18 o-l oo.l l6l 36.7 13.6 337 535 690 843 33. 0.3 7:t0.03 0.18+0.02 0.05 +0.01 0.0310.01 <0.02$ 1 41.0 46.8 'fSimazine treatment;4.48 kg (a.i.)/ha, 10 Junc 1968. +Means of four replications with standild errors. Correctcd for thc 957r recovery of the forlified checks $Sensitivity of the method. //From qeather records at location ofexperilnent residual simazine. On 23 November 1968 all plots were rotovated to a depth of approximate- ly 15 cm. Two weeks after sampling on 13 May 1969, plots were again rotovated as described above. The seedbed was prepared and on 5 June half of each plot was seeded to oats, and on 16 June the other half was seeded to corn (Zen mays L. ), beans (Pltaseoltts vrtlgaris L. ) and Swiss chard (Beta vrilgaris var. cicla L.). Recommended rates of fertilizer were applied. Random samples of corn kernels, oat grains and bean pods were obtained from each plot at harvest and frozen in plastic bags for later residue analyses. The plots were left without rotovation until spring 1970. Aftel soil sampling on I May 1970, plots were again rotovated as described earlier and the seedbed was prepared. In June, all the plots were sown with oats and observed throughout the season for simazine phytotoxicity. After thawing, the soil samples were airdried at room temperature, sieved through a 20-mesh screen, mixed thoroughly and subsampled for mechanicai analysis and simazine residue determinations. The textural analysis of Bouyoucos ( 195 1 ) The pH and percent organic matter content were determined by the glass electrode and was made by the method appropriate soil collection and crop sample by thin-layer chromatography (Abbot et al. 1965). RESULTS AND DISCUSSION The soil of the experimental plots was 707c sand, llak stlt and 19% clay. The percent organic matter was 2.9 and the pH value was 4,8. Chemical analysis of soil samples showed that there was a rapid reduction in simazine dr-rring the first 18 days after its incorporation into the soil at which time 537o of that initially applied was recovered (Table 1, Fig. 1). The rate of simazine dissipation between 18 and 63 days was still rapid in spite of the receipt of a very low amount (0.7 cm) of precipitation (rainfall). The amount of simazine had dropped to 0.80 ppm. This rapid rate of dissipation continued up to the third sampling at 161 days following which there was a more gradual loss of simazine until at 843 days no detectable residue was present. This pattern of simazine dissipation ,::- ."tt agrees with that found by Road- . dichromate oxidation, respectively (Atkinson et al. 1958), Simazine residue determinations in the soil and crop samples were performed colorimetrically using essentially the pyridine-alkali-ethyl cyanoacetate procedure as previousiy described (Ragab and Leefe 1972). Duplicate samples were analyzed from each plot and the analytical results *ere corrected for the recovery of the fortified untreated check samples. The analytical results were qualitatively confirmed on pooled cleane<l-uF extracts from each ;"1 tl;'"i ;l;.,1 \ \ d,"i I .,- \ --.-.-- ___-__ Fig. 1. Simazine residues in the top 15 cm of soil. 7t5 RAGAB-EFFECTS OF SIMAZINE RESIDUE ON CROPS Birk (1961) in Ontario irnd Clay and Stott (1973) in England. In the spring of 1969 when the various Can. J. Plant Sci. Downloaded from www.nrcresearchpress.com by 188.8.131.52 on 10/26/17 For personal use only. house and crops were planted the year following application, the soil contained 0.18 ppm simazine (Table 1). This residue was not harmful to the growth of corn. Swiss charcl did not grow, whereas beans and oats exhibited simazine toxicity with significantly lower yields than plants grown in untreated soil. The maturity of oats was delayed and the grains were still green at harvest. In no case was any appreciable residue of simazine detected in the crops (Table 2). Thus a residue of 0.18 ppm simazine in soil does not result in any detectable simazine in these crops. This study demonstrates that during the 1969 grou'ing season in Nova Sco,l.ia, simazine carryover from treatment in 1968 was detrimental to the growth of oats, beans and Swiss chard. Accordingly, it is strongly advised that such sensitive crops should not be planted 1 yr after simazine treatment. The results on crop toxicity are in agreement with those reported earlier by Roadhouse and Birk (1961), Fink and Fletchalt (1953), and Talbert and Fletchall (\964). Since plants are known to absorb, trans- locate and metabolize triazine herbicides (Montgomery and Freecl 1961; Ragab and McCollum l96l; Sikka and Davis 1966) cropping would definitely contribute to the loss of simazine activity in the r;oil. The amount of simazine left in the soil in November 1969 following these crops was 0.05 ppm (Table 1). This amount corresponds to 2.5Vo of the originally, applied sirnazine (Fig. 1). Almost 2 oat plants. Precipitation, cool temperatures, soil tex- ture, soil reactions and plant uptake by ciops are believed to be the major factors influencing the persistence of simazine in soil in the investigation reported herein. Since the simazine was incorporated into the soil, it is doubtful that volatilization or photochemical decomposition had contributed significantly to the disappearance of simazine from the soil. ABBOTT, D. C., BUNTING, J. A. (Mrs.) and THOMSON, I. 1965. The thin layer chromatographic determination 2. Apparent Recovery residue Crop (.qo)l 0Pm)t Corn kernels Oat grains 92.4 93.2 95.1 <0.02!i tMean of fou determinations. +Mean of eight determinations. $Sensitivity of thc method. of triazine herbicides in soil and water. Analyst 90: 356-361. ATKINSON, H. J., GILES, G. R., McLEAN, A. J. and WRIGHT, J. R. 1958. Chemical of soil analysis. Can. Dep. Agric., Ottawa, Onlario. 90 pp. BOUYOUCOS, C. J. 'l95 1. A lecalibration of the hydrometer method fol making mechanical analysis of soils. Agron. J. 43: 434-438. CLAY, D. V. and STOTT, K. G. 1973. The persistence and penetration of large doses of simazine in uncropped soil. Weed Res. l3: 42,50. methods FINK, R. J. and FLETCHAI-I-, O. H. 1963. Forage crops established in soil containing atrazine or simazine residues. Weeds 11: 81-83. FINK, R. J. and FLETCHALL, O. H. 1969. Soybean injury from triazine residues in soii. Weed Sci. 17: 35 36. L. C. and WHITESIDE, G. B. Soil survey of the Annapolis Valley fruit growing area. Can. Dep. Agric. Tech. Bull. 47 pp. HOI-LY, K. and ROBERTS, H. A. I963. Persistence of phytotoxic residues of triazine her1943. Residue of simazine in com. oatrs and beans grown in a sandy loam soil treated with 4.,18 kg (a.i.) simazine/ha in the previous;ear Bean pods 1970) after treat- somewhat detrimental to oats planted in June. Typical symptoms of simazine toxicity were present on a small percentage of the HARLOW, Table yr (l May ment, the amount of detectable simazine in the plots was 0.03 ppm (Table 1). This low amount of the retained simazine in soil was <0.02 <0.02 bicides in soil. Weed Res. 3: 1-10. MONTGOMERY, M. and FREED, V. H. 1961. The uptake, translocation and metabolism of simazine and atrazine by corn plants. Weeds 9: 231-237. RAGAB, M. T, H. and McCOLLUM, J. P. 1961. Degradation of C"-labelled simazine by plants and soil microorganisms. Weeds 9: 7284. 716 CANADIAN JOURNAL OF PLANT SCIENCE RAGAB, M. T. H. and LEEFE, J. S. 1972. Residues in soils and strawberries resulting from simazine applications. Can. J. Plant Sci. 52: 147-149. ROADHOUSE, F. E. B. and BIRK, L. A. 1961. Penetration and persistence in soil of the Can. J. Plant Sci. Downloaded from www.nrcresearchpress.com by 184.108.40.206 on 10/26/17 For personal use only. herbicide 2-chloro-4,6-bis (ethylamino)-s-tria- zine (Simazine). Can. J. Plant Scl 4l: 252- 260. SIKKA, H. C. and DAVIS, D. E. 1966. Dissipation of atrazine from soii by corn, sor- ghum, and Johnsongrass. Weeds 14: 289-293. TALBERT, R. E. and FLETCHALL, O. H. 1964. Inactivation of simazine and atrazine in the field. Weeds 12: 33-37.