Tolerance of carrot and red beet to s-metolachlor at three application timings—pre-emergence to crop (PRE), early postemergence (crop at two to four leaf stage-EPOST), and late postemergence (crop at five to seven le...Tolerance of carrot and red beet to s-metolachlor at three application timings—pre-emergence to crop (PRE), early postemergence (crop at two to four leaf stage-EPOST), and late postemergence (crop at five to seven leaf stage-LPOST) —was determined from 2008 to 2010. LPOST applications of s-metolachlor reduced carrot above ground plant dry weight, marketable yield and grower payment, but did not affect carrot length. PRE and LPOST applications of s-metolachlor reduced red beet above ground plant dry weight, total marketable yield, yield of No. 2 and No. 3 red beet, and grower payment. Our findings indicate that while carrot may be tolerant to PRE applications of s-metolachlor, applications made after the 5 leaf stage reduced plant dry weight enough to impact marketable yield and grower payment. In red beet, the potential reduction in growth, yield and grade would not justify the utility of a PRE or LPOST applica- tion timing.展开更多
The fate of the herbicide metolachlor in aerobic and anaerobic soils with repeated applications of the metolachlor over a period of 5 years was studied. After 12 weeks incubation, cumulative 14CO2 evolution from the s...The fate of the herbicide metolachlor in aerobic and anaerobic soils with repeated applications of the metolachlor over a period of 5 years was studied. After 12 weeks incubation, cumulative 14CO2 evolution from the soil accounts for 8.01% in aerobic condition versus 1.5% of 14CO2 in the soil had not been treated with metolachlor. The total 14C recovery in the methanol-water extract and in the non-extractable portion of this aerobic soil accounted for 73.1% and the total metolachlor recovery in the methanol-water extract was 46.7% but 86.9% of 14C was accounted for in the γ-irradiated control soil. There axe no differences in the recovery of 14C between non-sterile and γ-irradiated control soil under anaerobic conditions. The results show that there was some active metolachlor-degrading population in the Virginia soil which had been previously received repeated applications of the metolachlor but only under aerobic condition.展开更多
A preliminary study conducted in the central USA near Colby and Hays, Kansas (KS) in 2010 indicated a premix of S-metolachlor & sulfentrazone codenamed F7583 (Broadaxe?) had good potential for use in sunflower (He...A preliminary study conducted in the central USA near Colby and Hays, Kansas (KS) in 2010 indicated a premix of S-metolachlor & sulfentrazone codenamed F7583 (Broadaxe?) had good potential for use in sunflower (Helianthus annuus L.). Additional studies were conducted in 2011 at Colby, Hays, Manhattan, KS to refine rate and application timing of F7583 for weed control and crop safety. Four rates of F7583 (860, 1100, 1350 and 1840 g·ha-1) were compared to single rates of S-metolachlor and pendimethalin, and applied 21 days preplant versus preemergence (PRE). F7583 at ≥1100 g·ha-1 applied preplant or PRE controlled Palmer amaranth (Amaranthus palmeri S. Wats.) and kochia [Kochia scoparia (L.) Schrad.] ≥95% and 100%, respectively in neutral pH soils. In slightly acidic soils, PRE application of F7583 was more effective against Palmer amaranth and grass weeds compared to preplant application. No benefit was gained by increasing the rate of F7583 from 1100 to 1350 g·ha-1 at either application timing. Puncturevine (Tribulus terrestris L.) control was not commercially satisfactory with F7583 at any rate or time of application. Both S-metolachlor at 1070 g·ha-1 and pendimethalin at 1600 g·ha-1 applied either preplant or PRE were considerably less effective on all three broadleaf weeds compared to F7583 treatments. Individually, S-metolachlor and pendimethalin were more effective when applied PRE compared to preplant application. F7583 did not reduce sunflower plant population or visibly injure sunflower anytime during the season.展开更多
The S-metolachlor is used to control/suppress yellow nutsedge, annual grasses, and several broadleaf weeds in sweetpotato. However, when used under adverse environmental conditions, it may lead to crop injury. Informa...The S-metolachlor is used to control/suppress yellow nutsedge, annual grasses, and several broadleaf weeds in sweetpotato. However, when used under adverse environmental conditions, it may lead to crop injury. Information is limited on the effect of S-metolachlor application followed immediately by rainfall on sweetpotato growth and development under different temperature regimes. The objective of this study was to determine sweetpotato response to S-metolachlor under low, optimum, and high temperatures with no rainfall and rainfall immediately after application. Sweetpotato slips were transplanted to sandy loam soil-filled pots. Half of the pots were subjected to 38 mm rainfall at 50.8 mm·h-1 intensity within the first 24 h after POST-transplant S-metolachlor application at 0, 0.86, 1.72, 2.58 and 3.44 kg·ha-1. The pots were moved into sunlit, computer-controlled plant growth chambers that were maintained at their respective temperatures for 61 days. Plant growth, development and plant-component dry weights and quantity of storage roots were recorded at harvest. Storage root yield was highest at the optimum temperature and declined at low and high temperature conditions. Shoot, root, and total plant biomass yield declined with increasing concentration of S-metolachlor across temperature conditions. In addition, storage root yield decline was S-metolachlor rate-dependent and aggravated by a rainfall event immediately after herbicide treatment across temperatures tested. These results can be used to weigh the risk of potential crop injury against the benefits of S-metolachlor when making management decisions as well as considering weather forecast information to avoid herbicide application coinciding with adverse weather conditions such as excessive rainfall event.展开更多
Separation of chiral enantiomers and the dissipation of rac-metolachlor and S-metolachlor in soil were evaluated using achiral high-performance liquid chromatography (HPLC) and chiral gas chromatography (GC) methods. ...Separation of chiral enantiomers and the dissipation of rac-metolachlor and S-metolachlor in soil were evaluated using achiral high-performance liquid chromatography (HPLC) and chiral gas chromatography (GC) methods. Under the experimental conditions the possible metabolite was considered to be N-(2-ethyl-6-methyl-phenyl)-2-hydroxy-acetamide. Because of the presence of two chiral elements (asymmetrically substituted carbon and chiral axis), the baseline separation of metolachlor enantiomers was not achieved. S-metolachlor degraded faster in soil than rac-metolachlor. After a 42-day incubation, 73.4% of rac-metolachlor and 90.0% of S-metolachlor were degraded. However, due to the absence of biological processes the degradation process in sterilized soil showed no enantioselectivity. The results indicated that enantioselective degradations could greatly affect the environmental fate of metolachlor and should be considered when the environmental behavior of these compounds was assessed.展开更多
Field studies were conducted to determine the dissipation and movement of metribuzin and metolachlor applied at conventional rates to a Verndale sandy loam (Udic Argiboroll) in north-central Minnesota under irrigated ...Field studies were conducted to determine the dissipation and movement of metribuzin and metolachlor applied at conventional rates to a Verndale sandy loam (Udic Argiboroll) in north-central Minnesota under irrigated potato production in two years. The rapid dissipation of both metribuzin and metolachlor was found during the initial 10 to 15 days in both years) and more than 70% of the applied herbicide dissipated during this period. From 10 to 15 days after application up to the end of growing season in both years, the levels of both herbicides decreased slowly with time. Metolachlor dissipated at a slower rate than metribuzin in surface soil and could carry over to the next cropping season. Metribuzin and metolachlor were detected in only 6 and 1 of 154 soil samples in the first year and in 3 and 4 of 225 soil samples in the second year, taken from 15 to 75cm, respectively. Fifty to 67% of water samples from suction samplers at 135-cm depth contained detectable levels (>0.4μg L-1 ) of herbicides in both years. Under laboratory conditions degradation of both herbicides was much slower than their dissipation in field. Therefore, it appeared that leaching might be an important dissipation pathway for metribuzin and metolachlor under irrigated potato production.展开更多
Metolachlor retention on a Sharkey clay soil was quantified using a kinetic batch method for different initial solution concentrations. Time-dependent adsorption was carried out by monitoring solution concentration at...Metolachlor retention on a Sharkey clay soil was quantified using a kinetic batch method for different initial solution concentrations. Time-dependent adsorption was carried out by monitoring solution concentration at different reaction times. Adsorption was found to be highly kinetic in nature. Attempts were made to describe metolachlor retention based on a kinetic multireaction model which includes reversible and irreversible retention processes of the equilibrium and kinetic types. The predictive capability of the model for the description of experimental results for metolachlor retention was examined and proved to be adequate.展开更多
文摘Tolerance of carrot and red beet to s-metolachlor at three application timings—pre-emergence to crop (PRE), early postemergence (crop at two to four leaf stage-EPOST), and late postemergence (crop at five to seven leaf stage-LPOST) —was determined from 2008 to 2010. LPOST applications of s-metolachlor reduced carrot above ground plant dry weight, marketable yield and grower payment, but did not affect carrot length. PRE and LPOST applications of s-metolachlor reduced red beet above ground plant dry weight, total marketable yield, yield of No. 2 and No. 3 red beet, and grower payment. Our findings indicate that while carrot may be tolerant to PRE applications of s-metolachlor, applications made after the 5 leaf stage reduced plant dry weight enough to impact marketable yield and grower payment. In red beet, the potential reduction in growth, yield and grade would not justify the utility of a PRE or LPOST applica- tion timing.
文摘The fate of the herbicide metolachlor in aerobic and anaerobic soils with repeated applications of the metolachlor over a period of 5 years was studied. After 12 weeks incubation, cumulative 14CO2 evolution from the soil accounts for 8.01% in aerobic condition versus 1.5% of 14CO2 in the soil had not been treated with metolachlor. The total 14C recovery in the methanol-water extract and in the non-extractable portion of this aerobic soil accounted for 73.1% and the total metolachlor recovery in the methanol-water extract was 46.7% but 86.9% of 14C was accounted for in the γ-irradiated control soil. There axe no differences in the recovery of 14C between non-sterile and γ-irradiated control soil under anaerobic conditions. The results show that there was some active metolachlor-degrading population in the Virginia soil which had been previously received repeated applications of the metolachlor but only under aerobic condition.
文摘A preliminary study conducted in the central USA near Colby and Hays, Kansas (KS) in 2010 indicated a premix of S-metolachlor & sulfentrazone codenamed F7583 (Broadaxe?) had good potential for use in sunflower (Helianthus annuus L.). Additional studies were conducted in 2011 at Colby, Hays, Manhattan, KS to refine rate and application timing of F7583 for weed control and crop safety. Four rates of F7583 (860, 1100, 1350 and 1840 g·ha-1) were compared to single rates of S-metolachlor and pendimethalin, and applied 21 days preplant versus preemergence (PRE). F7583 at ≥1100 g·ha-1 applied preplant or PRE controlled Palmer amaranth (Amaranthus palmeri S. Wats.) and kochia [Kochia scoparia (L.) Schrad.] ≥95% and 100%, respectively in neutral pH soils. In slightly acidic soils, PRE application of F7583 was more effective against Palmer amaranth and grass weeds compared to preplant application. No benefit was gained by increasing the rate of F7583 from 1100 to 1350 g·ha-1 at either application timing. Puncturevine (Tribulus terrestris L.) control was not commercially satisfactory with F7583 at any rate or time of application. Both S-metolachlor at 1070 g·ha-1 and pendimethalin at 1600 g·ha-1 applied either preplant or PRE were considerably less effective on all three broadleaf weeds compared to F7583 treatments. Individually, S-metolachlor and pendimethalin were more effective when applied PRE compared to preplant application. F7583 did not reduce sunflower plant population or visibly injure sunflower anytime during the season.
文摘The S-metolachlor is used to control/suppress yellow nutsedge, annual grasses, and several broadleaf weeds in sweetpotato. However, when used under adverse environmental conditions, it may lead to crop injury. Information is limited on the effect of S-metolachlor application followed immediately by rainfall on sweetpotato growth and development under different temperature regimes. The objective of this study was to determine sweetpotato response to S-metolachlor under low, optimum, and high temperatures with no rainfall and rainfall immediately after application. Sweetpotato slips were transplanted to sandy loam soil-filled pots. Half of the pots were subjected to 38 mm rainfall at 50.8 mm·h-1 intensity within the first 24 h after POST-transplant S-metolachlor application at 0, 0.86, 1.72, 2.58 and 3.44 kg·ha-1. The pots were moved into sunlit, computer-controlled plant growth chambers that were maintained at their respective temperatures for 61 days. Plant growth, development and plant-component dry weights and quantity of storage roots were recorded at harvest. Storage root yield was highest at the optimum temperature and declined at low and high temperature conditions. Shoot, root, and total plant biomass yield declined with increasing concentration of S-metolachlor across temperature conditions. In addition, storage root yield decline was S-metolachlor rate-dependent and aggravated by a rainfall event immediately after herbicide treatment across temperatures tested. These results can be used to weigh the risk of potential crop injury against the benefits of S-metolachlor when making management decisions as well as considering weather forecast information to avoid herbicide application coinciding with adverse weather conditions such as excessive rainfall event.
基金Supported by the National Science Fund for Distinguished Young Scholars (No. 20225721) and the National Natural Science Foundation of China (No. 30270767).
文摘Separation of chiral enantiomers and the dissipation of rac-metolachlor and S-metolachlor in soil were evaluated using achiral high-performance liquid chromatography (HPLC) and chiral gas chromatography (GC) methods. Under the experimental conditions the possible metabolite was considered to be N-(2-ethyl-6-methyl-phenyl)-2-hydroxy-acetamide. Because of the presence of two chiral elements (asymmetrically substituted carbon and chiral axis), the baseline separation of metolachlor enantiomers was not achieved. S-metolachlor degraded faster in soil than rac-metolachlor. After a 42-day incubation, 73.4% of rac-metolachlor and 90.0% of S-metolachlor were degraded. However, due to the absence of biological processes the degradation process in sterilized soil showed no enantioselectivity. The results indicated that enantioselective degradations could greatly affect the environmental fate of metolachlor and should be considered when the environmental behavior of these compounds was assessed.
基金Project supported by the Legislative Commission on Minnesota Resources, USA the Teaching and ResearchAward Program for Outsta
文摘Field studies were conducted to determine the dissipation and movement of metribuzin and metolachlor applied at conventional rates to a Verndale sandy loam (Udic Argiboroll) in north-central Minnesota under irrigated potato production in two years. The rapid dissipation of both metribuzin and metolachlor was found during the initial 10 to 15 days in both years) and more than 70% of the applied herbicide dissipated during this period. From 10 to 15 days after application up to the end of growing season in both years, the levels of both herbicides decreased slowly with time. Metolachlor dissipated at a slower rate than metribuzin in surface soil and could carry over to the next cropping season. Metribuzin and metolachlor were detected in only 6 and 1 of 154 soil samples in the first year and in 3 and 4 of 225 soil samples in the second year, taken from 15 to 75cm, respectively. Fifty to 67% of water samples from suction samplers at 135-cm depth contained detectable levels (>0.4μg L-1 ) of herbicides in both years. Under laboratory conditions degradation of both herbicides was much slower than their dissipation in field. Therefore, it appeared that leaching might be an important dissipation pathway for metribuzin and metolachlor under irrigated potato production.
文摘Metolachlor retention on a Sharkey clay soil was quantified using a kinetic batch method for different initial solution concentrations. Time-dependent adsorption was carried out by monitoring solution concentration at different reaction times. Adsorption was found to be highly kinetic in nature. Attempts were made to describe metolachlor retention based on a kinetic multireaction model which includes reversible and irreversible retention processes of the equilibrium and kinetic types. The predictive capability of the model for the description of experimental results for metolachlor retention was examined and proved to be adequate.
