The Study On Screening Perfect Chemical Herbicides Of Linearstripe Rabdosia Herb And Residue Behavior In Linearstripe Rabdosia Herb And Soil

This article has firstly conducted the screening research of suitable chemical herbicides for controlling weeds in Linearstrip Rabdosia Herb field, studied the dynamics of herbicides in Linearsreipe Rabdosia Herb and soil, provided certain scientific data to establish the standard for safe application of herbicides.The results showed that Haloxyfop-R-methyl, Prometryn, Pendimethalin and Bentazone were the suitable chemistry herbicides. The recommended dose of 40% Prometryn WP was 80 g/667m2 for pre-sowing. The recommended dose of 40%Prometryn WP,33% Pendimethalin EC was 100 g/667m2,100 mL/667m2 for pre-transplant. The recommended dose of 10.8% Haloxyfop-R-methyl EC or 48% Bentazone WG was 40 mL/667m2 or 100 mL/667m2 respectively for post-emergence.Residues of Haloxyfop-R-methyl and Pendimethalin in both Linearstripe Rabdosia Herb and soil were determined by gas chromatography with ECD.The fortified recoveries of haloxyfop-R-methyl in Linearstripe Rabdosia Herb or soil were in range of 87.61%～ 98.71%,92.06%～103.51%, with relative standard deviations of 4.07%～6.06%,2.54%～ 4.97%. The limit of quantification of Linearstripe Rabdosia Herb and soil was 0.01mg/kgand 0.005mg/kg. The fortified recoveries of pendimethalin in Linearstripe Rabdosia Herb and soil were in range of 84.92%～95.34%,89.92%～101.34%, with relative standard deviations of 3.13%～4.19%,4.67%～5.39%. The limit of quantification of Linearstripe Rabdosia Herb and soil was both 0.01mg/kg. Residues of bentazone in both Linearstripe Rabdosia Herb and soil were determined by HPLC with UV. The fortified recoveries of bentazone in Linearstripe Rabdosia Herb or soil were in range of 83.44%-89.64%,92.18%～97.84%, with relative standard deviations of 1.17%～2.98%,1.46%～ 2.38%. The limit of quantification of Linearstripe Rabdosia Herb and soil was 0.01mg/kg and 0.005mg/kg.According to the result of tests under the temperature of 10,20,30℃,the higher temperature was, the faster degrading speed was. The half-lives of Haloxyfop-R-methyl in soil were 2.38 d (10℃),2.10 d (20℃),1.84 d (30℃). The half-lives of Pendimethalin in soil were 12.96 d(10℃),11.93 d(20℃),10.34 d(30℃). The half-lives of Bentazone in soil were 17.30 d (10℃),15.79 d (20℃),13.97 d (30℃)The dynamics of Haloxyfop-R-methyl, Pendimethalin and Bentazone in both sterilized and unsterilized soils showed that the half-lives of Haloxyfop-R-mehyl were 2.63 d (sterilized),2.10 d (unsterilized); the half-lives of Pendimethalin were 13.53 d (sterilized),11.93 d(unsterilized); the half-lives of Bentazone were 17.57 d (sterilized), 15.79 d (unsterilized)Results of field test showed that the half-lives of Haloxyfop-R-methyl were 1.52 d (900 mL/hm2) and 1.59 d (600 mL/hm2) in Linearstripe Rabdosia Herb. The residue of Haloxyfop-R-methyl in both Linearstripe Rabdosia Herb and soil was degraded below 0.05mg/kg after 21 days, so the recommended safe inteval was at least 21 days. The half-lives of Pendimethalin were 3.32 d(1500 mL/hm2),3.41 d(2250 mL/hm2)in soil. The residue of Pendimethalin in both Linearstripe Rabdosia Herb and soil was degraded below 0.01 mg/kg at harvest. The half-lives of Bentazone were 1.98 d (1500 mL/hm2),2.08 d (2250 mL/hm2) in Linearstripe Rabdosia Herb,3.31 d (1500 mL/hm2) and 3.30 d (2250 mL/hm2) in soil. The bentazone residue in both Linearstripe Rabdosia Herb and soil was degraded below O.Olmg/kg after 30 days, so the recommended safe interval was at least 30 days.