Tillage management to mitigate herbicide loss in runoff under simulated rainfall conditions

Conservation tillage mitigates soil loss in cropland because plant residues help protect the soil, but effects on pesticide movement in surface runoff are not as straightforward. Effects of soil disturbance on surface runoff loss of chlorimuron and alachlor were evaluated utilizing runoff trays. Soil in the trays was either disturbed (tilled) and kept bare or was not tilled, and existing decomposed plant residue was left on the surface. Rainfall (25mm, 20min) was simulated 1d after alachlor (2.8kg ha(-1)) or chlorimuron (54g ha(-1)) application, and runoff was collected. Runoff fractions were analyzed for herbicide and sediment. Total alachlor loss from bare plots was greater than that in no-tillage plots (4.5% vs. 2.3%, respectively). More than one-third of total alachlor lost from bare plots occurred in the first l of runoff, while no-tillage plots had less runoff volume with a more even distribution of alachlor concentration in the runoff during the rainfall simulation and subsequent runoff period. In contrast, more chlorimuron was lost from no-tillage plots than bare plots (12% vs. 1.5%) even though total runoff volume was lower in the no-tillage plots (10.6mm vs. 13.6mm). This was attributed to dense coverage with partially decomposed plant residue in no-tillage plots (1652kg ha(-1)) that intercepted chlorimuron. It was likely that chlorimuron, a polar compound, was more easily washed off surface plant residues and transported in runoff.     

Dissipation of epoxiconazole in the paddy field under subtropical conditions of Taiwan

The environmental fate and distribution of fungicide epoxiconazole were studied by a rice paddy field model ecosystem. One week before the head-sprouting stage, rice plant was treated separately once with OPUS (tradename of epoxiconazole) 12% SC 2.1 kg ha(-1) and 1.4 kg ha(-1), respectively. Soil, water and rice plant were sampled seven days intervals nine times after application. The bioconcentration factor of epoxiconazole on mosquito fish in the ecosystem was also determined, based on the amounts of epoxiconazole content both in fish and water. This was initiated one day after the fungicide treatment, and continued for four days. In addition, the residue of epoxiconazole in rice grains was analyzed after harvest. After harvest, both planted water spinach (Ipomoea aquatica Forsk) and edible amaranth (Amaranthus mangostanüs L.) were analyzed. The results showed that epoxiconazole degraded in the local environment under the experimental conditions described. The degradation equations were in accordance with the first order kinetics. The DT50 of soil, field water and rice plant were 20-69 days, 11-20 days and 14-39 days, respectively. The bioconcentration factors of epoxiconazole on mosquito fish were 12.9 and 10.6 from 2.1 kg ha(-1) and 1.4 kg ha(-1) treatment, respectively. Residues of epoxiconazole in both rice and harvest vegetables were non-detectable. This indicates that epoxiconazole applied to rice at the recommended rates and application frequencies will not accumulate on rice grain and successive cropping vegetables.     

Fate of anilide and aniline herbicides in plant-materials-amended soils

The fate of herbicides trifluralin, pendimethalin, alachlor and metolachlor in paddy field soils amended with plant materials was investigated. The plant materials were purple sesbania, vegetable soybean and rice straw. The investigation was performed at two temperatures (25 and 40 degrees C) and two soil water moistures (60 and 90% water-holding capacity). The results showed linear and Freudlich equations described the adsorption of amide compound to soil. Adsorption coefficient (K(d)) fit to linear equation were in general greater in plant material-amended soils than in non-amended soil, especially in soil amending with rice straw. Increasing temperature and soil water moisture content shortened the half-lives of compounds in various treated soils. The movement of compounds in the soil columns showed the maximum distribution of aniline type compound, trifluralin and pendimethalin, appeared at the upper top of 0 to 5 and 0 to 10 cm of soil column, respectively, and of anilide type, alachlor and metolachlor, were distributed at 0 to 25 cm of the soil column. The mobility of chemicals in the different treated soils was simulated by the behavior assessment model (BAM). There was no significant difference among different plant material incubated soils on dissipation and mobility of compounds in soils.     

Behavior of bensulfuron-methyl in an agricultural alkaline soil

A field experiment to determine the available bensulfuron-methyl (BSM) in the upper soil layer was conducted in an agricultural area in the South of Spain. To facilitate herbicide analysis, two application rates were employed, 200 g ha^?1 and 5 kg ha^?1. Samples of upper soil and soil solution were collected. Soil solution was sampled by means of metallic samplers, placed at a depth of 35 cm. In the plots receiving the lower dose ceramic suction, porous cups were also installed. Results from soil solution samples showed that the maximum BSM concentration was found after 8-10 days for the high irrigation supply (945 mm) and after 18-25 days for the lower irrigation regime (405 mm). The mathematical model FOCUSPELMO 1.1.1 was applied to interpret the data obtained in the field experiments. In general, there was a reasonable agreement between experimental and simulated data for soil samples, although the model did not acceptably predict herbicide concentrations in water soil samples. Ceramic cups sampled a higher soil water volume and more frequently than did the metallic samplers. However some variable results were attributed to preferential flow.     

Behavior of bensulfuron-methyl in an agricultural alkaline soil

A field experiment to determine the available bensulfuron-methyl (BSM) in the upper soil layer was conducted in an agricultural area in the South of Spain. To facilitate herbicide analysis, two application rates were employed, 200 g ha(-1) and 5 kg ha(-1). Samples of upper soil and soil solution were collected. Soil solution was sampled by means of metallic samplers, placed at a depth of 35 cm. In the plots receiving the lower dose ceramic suction, porous cups were also installed. Results from soil solution samples showed that the maximum BSM concentration was found after 8-10 days for the high irrigation supply (945 mm) and after 18-25 days for the lower irrigation regime (405 mm). The mathematical model FOCUSPELMO 1.1.1 was applied to interpret the data obtained in the field experiments. In general, there was a reasonable agreement between experimental and simulated data for soil samples, although the model did not acceptably predict herbicide concentrations in water soil samples. Ceramic cups sampled a higher soil water volume and more frequently than did the metallic samplers. However some variable results were attributed to preferential flow.     

Determination of sulfosulfuron residues in soil under wheat crop by a novel and cost-effective method and evaluation of its carryover effect

A novel and cost-effective method of sulfosulfuron extraction has been developed using distilled water as an extraction solvent. Using this method, the environmental fate of sulfosulfuron was investigated in soil under wheat crop. Studies were conducted under natural field conditions in randomized block design and herbicide (75% water dispersible granules (WG)) was applied after 24 days of sowing. The rates of applications were 25 and 50 g of active ingredient (a.i.) per hectare. Soil samples were collected at predetermined intervals and analyzed by high performance liquid chromatography (HPLC). The minimum detection limit was found to be 0.001 micro g g(-1). The dissipation of sulfosulfuron followed first-order rate kinetics and dissipated with a half-life of 5.4-6.3 days. After harvest, field soil was used for conducting a pot experiment with bottle gourd (Lagenaria siceraria) as test plants to study the carry over effect of sulfosulfuron. No phytotoxicity was observed to bottle gourd in pot experiment with harvest soil.     

Persistence,mobility, efficacy and activity of chloroacetanilide herbicide formulation under greenhouse and field experiments

Persistence, stability, mobility and activity characteristics of organoclay and commercial formulation of alachlor were evaluated in soil columns and field plots in Gaza, Palestine. Relative concentrations of alachlor were accumulated in the top soil as determined by bioassay and consequently its mobility was retarded in soil treated with organoclay formulation. Alachlor applied as commercial EC formulation readily distributed through the soil media to a deeper depth. The herbicidal activity of alachlor applied as organoclay formulation was limited to the top soil whereas it disappeared from the top soil in plots treated with EC commercial formulation. Greenhouse and field experiments showed persistence, reduced mobility, safe and effective herbicide formulation at a significantly reduced applied rate when alachlor was applied as organoclay formulation.     

Determination of sulfosulfuron residues in soil under wheat crop by a novel and cost-effective method and evaluation of its carryover effect

A novel and cost-effective method of sulfosulfuron extraction has been developed using distilled water as an extraction solvent. Using this method, the environmental fate of sulfosulfuron was investigated in soil under wheat crop. Studies were conducted under natural field conditions in randomized block design and herbicide (75% water dispersible granules (WG)) was applied after 24 days of sowing. The rates of applications were 25 and 50 g of active ingredient (a.i.) per hectare. Soil samples were collected at predetermined intervals and analyzed by high performance liquid chromatography (HPLC). The minimum detection limit was found to be 0.001 μ g g^{? 1}. The dissipation of sulfosulfuron followed first-order rate kinetics and dissipated with a half-life of 5.4–6.3 days. After harvest, field soil was used for conducting a pot experiment with bottle gourd (Lagenaria siceraria) as test plants to study the carry over effect of sulfosulfuron. No phytotoxicity was observed to bottle gourd in pot experiment with harvest soil.     

Fate of anilide and aniline herbicides in plant-materials-amended soils

The fate of herbicides trifluralin, pendimethalin, alachlor and metolachlor in paddy field soils amended with plant materials was investigated. The plant materials were purple sesbania, vegetable soybean and rice straw. The investigation was performed at two temperatures (25 and 40°C) and two soil water moistures (60 and 90% water-holding capacity). The results showed linear and Freudlich equations described the adsorption of amide compound to soil. Adsorption coefficient (K _d ) fit to linear equation were in general greater in plant material-amended soils than in non-amended soil, especially in soil amending with rice straw. Increasing temperature and soil water moisture content shortened the half-lives of compounds in various treated soils. The movement of compounds in the soil columns showed the maximum distribution of aniline type compound, trifluralin and pendimethalin, appeared at the upper top of 0 to 5 and 0 to 10 cm of soil column, respectively, and of anilide type, alachlor and metolachlor, were distributed at 0 to 25 cm of the soil column. The mobility of chemicals in the different treated soils was simulated by the behavior assessment model (BAM). There was no significant difference among different plant material incubated soils on dissipation and mobility of compounds in soils.     

Metolachlor persistence in laboratory and field soils under Indian tropical conditions

Metolachlor [2-chloro-N-(2-methoxy-1-methylethyl)-2'-ethyl-6'- methyl acetanilide] dissipation under both field and laboratory conditions were studied during summer season in an Indian soil. Metolachlor was found to have moderate persistence with a half-life of 27 days in field. The herbicide got leached down to 15-30 cm soil layer and residues were found up to harvest day of the sunflower crop in both 0-15 cm and 15-30 cm soil layers. Metolachlor was found to be more persistent in laboratory studies conducted for 190 days. The rate of degradation was faster in soil under flooded partial anaerobic conditions as compared to aerobic soil with a half-life of 44.3 days. In aerobic soil, metolachlor was very stable with only 49% dissipation in 130 days. Residues remained in both the soils up to the end of the experimental period of 190 days.     

Runoff and leaching of atrazine and alachlor on a sandy soil as affected by application in sprinkler irrigation

Rainfall simulation was used with small packed boxes of soil to compare runoff of herbicides applied by conventional spray and injection into sprinkler-irrigation (chemigation), under severe rainfall conditions. It was hypothesized that the larger water volumes used in chemigation would leach some of the chemicals out of the soil surface rainfall interaction zone, and thus reduce the amounts of herbicides available for runoff. A 47-mm rain falling in a 2-hour event 24 hours after application of alachlor (2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)-acetamide) and atrazine (6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2, 4-diamine) was simulated. The design of the boxes allowed a measurement of pesticide concentrations in splash water throughout the rainfall event. Initial atrazine concentrations exceeding its' solubility were observed. When the herbicides were applied in 64,000 L/ha of water (simulating chemigation in 6.4 mm irrigation water) to the surface of a Tifton loamy sand, subsequent herbicide losses in runoff water were decreased by 90% for atrazine and 91% for alachlor, as compared to losses from applications in typical carrier water volumes of 187 L/ha. However, this difference was not due to an herbicide leaching effect but to a 96% decrease in the amount of runoff from the chemigated plots. Only 0.3 mm of runoff occurred from the chemigated boxes while 7.4 mm runoff occurred from the conventionally-treated boxes, even though antecedent moisture was higher in the former. Two possible explanations for this unexpected result are (a) increased aggregate stability in the more moist condition, leading to less surface sealing during subsequent rainfall, or (b) a hydrophobic effect in the drier boxes. In the majority of these pans herbicide loss was much less in runoff than in leachate water. Thus, in this soil, application of these herbicides by chemigation would decrease their potential for pollution only in situations where runoff is a greater potential threat than leaching.     

Atrazine and metolachlor residues in brookston Cl following conventional and conservation tillage culture

Atrazine and metolachlor are extensively used in Ontario, Canada for control of broadleaf weeds and annual grasses in corn. Conservation tillage may alter the physical and biological environment of soil affecting herbicide dissipation. The rate of dissipation of these two herbicides in soil from conventional, ridge and no-tillage culture was followed. Herbicide dissipation was best described by first order reaction kinetics. Half life, the time for herbicide residues to dissipate to half their initial concentration, was unaffected by tillage. Half life for atrazine and metolachlor was similar and ranged from 31 to 66 d. The rate of dissipation decreased in dry years when soil moisture content was low. In a dry year, herbicide residues during the growing season were significantly greater on ridge tops than in the other tillage treatments. However, after harvest no differences in herbicide residues were detected among tillage treatments. Residues of atrazine (6 to 9% of applied) and metolachlor (4 to 6%) were detected in soil before planting a year after application. De-ethyl atrazine, the primary degradation product of atrazine, increased in concentration during the growing season with the greatest concentrations measured at harvest and in years when atrazine dissipated fastest. De-ethyl atrazine one year after application accounted for about 12% of the remaining triazine residue. These herbicide residues would not be phytotoxic to subsequent crops but are a potential source for leaching to ground and surface waters.     

Runoff and leaching of atrazine and alachlor on a sandy soil as affected by application in sprinkler irrigation

Abstract

Rainfall simulation was used with small packed boxes of soil to compare runoff of herbicides applied by conventional spray and injection into sprinkler‐irrigation (chemigation), under severe rainfall conditions. It was hypothesized that the larger water volumes used in chemigation would leach some of the chemicals out of the soil surface rainfall interaction zone, and thus reduce the amounts of herbicides available for runoff. A 47‐mm rain falling in a 2‐hour event 24 hours after application of alachlor (2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)‐acetamide) and atrazine (6‐chloro‐N‐ethyl‐N‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine) was simulated. The design of the boxes allowed a measurement of pesticide concentrations in splash water throughout the rainfall event. Initial atrazine concentrations exceeding its’ solubility were observed. When the herbicides were applied in 64000 L/ha of water (simulating chemigation in 6.4 mm irrigation water) to the surface of a Tifton loamy sand, subsequent herbicide losses in runoff water were decreased by 90% for atrazine and 91% for alachlor, as compared to losses from applications in typical carrier water volumes of 187 L/ha. However, this difference was not due to an herbicide leaching effect but to a 96% decrease in the amount of runoff from the chemigated plots. Only 0.3 mm of runoff occurred from the chemigated boxes while 7.4 mm runoff occurred from the conventionally‐treated boxes, even though antecedent moisture was higher in the former. Two possible explanations for this unexpected result are (a) increased aggregate stability in the more moist condition, leading to less surface sealing during subsequent rainfall, or (b) a hydrophobic effect in the drier boxes. In the majority of these pans herbicide loss was much less in runoff than in leachate water. Thus, in this soil, application of these herbicides by chemigation would decrease their potential for pollution only in situations where runoff is a greater potential threat than leaching.     

Occurrence and distribution of trifluralin,ethalfluralin, and pendimethalin in soils used for long-term intensive cotton cultivation in central Greece

In the present study, a soil monitoring program was undertaken in Greek cotton cultivated areas in 2012. Twenty-seven soil samples were collected from the entire Thessaly plain in early summer of 2012, corresponding to approximately three months (current use of pendimethalin), up to one year (for the banned ethalfluralin), and three years (for the also banned trifluralin), after the last dinitroaniline application. Low but not negligible levels of dinitroanilines were detected, ranging from 0.01 to 0.21 μg g^?1 d.w. for trifluralin and 0.01–0.048 μg g^?1 d.w. for pendimethalin, respectively. Trifluralin was the herbicide most frequently detected (44.4%). The high historic application of trifluralin and its high persistence and accumulation potential is in line with the abundance of the detected residues. The present data indicate that soil samples contain extractable residues of banned trifluralin, but based on the comparison of the theoretical PECplateau for trifluralin (0.277 µg g^?1) and the maximum Measured Environmental Concentration, it was concluded that the detected residues should be attributed to previous years’ application. The latter suggested the need for continual monitoring of the dinitroaniline family of pesticides, including the banned substances, aiming thus to an improved environmental profile for agricultural areas.     

Metolachlor persistence in laboratory and field soils under Indian tropical conditions

Abstract

Metolachlor [2‐chloro‐N‐(2‐methoxy‐1‐methylethyl)‐2'‐ethyl‐6'‐methyl acetanilide] dissipation under both field and laboratory conditions were studied during summer season in an Indian soil. Metolachlor was found to have moderate persistence with a half‐life of 27 days in field. The herbicide got leached down to 15–30 cm soil layer and residues were found up to harvest day of the sunflower crop in both 0–15 cm and 15–30 cm soil layers. Metolachlor was found to be more persistent in laboratory studies conducted for 190 days. The rate of degradation was faster in soil under flooded partial anaerobic conditions as compared to aerobic soil with a half‐life of 44.3 days. In aerobic soil, metolachlor was very stable with only 49% dissipation in 130 days. Residues remained in both the soils up to the end of the experimental period of 190 days.     

Assessment of metolachlor and diuron leaching in a tropical soil using undisturbed soil columns under laboratory conditions

In the present study, diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-metoxi-1-methylethyl)acetamide] leaching was studied in undisturbed soil columns collected in a cotton crop area in Mato Grosso State, Brazil. The pesticides were applied to the soil surface in dosages similar to those used in a cotton plantation. To assess the leaching process, soil columns were submitted to simulated rain under laboratory conditions at 25 ± 3°C, in the absence of wind and direct solar radiation. During the rain simulations, leachate solutions were collected and herbicide concentrations were determined. At the end of the experiment, the soil columns were cut into 10 cm sections to determine the remaining herbicide concentrations through the soil profile. Metolachlor was detected in all soil sections, and approximately 4% of the applied mass was leached. Diuron was detected only in the upper two soil sections and was not detected in the leachate. A linear correlation (r > 0.94) between the metolachlor soil concentrations and the organic contents of the soil sections was observed. Mass balance suggests that around 56% of diuron and 40% of metolachlor were degraded during the experiments. Measurements of the water table depth in the area where the samples were collected showed that it varied from 2 to 6 m and is therefore vulnerable to contamination by the studied herbicides, particularly metolachlor, which demonstrated a higher leaching potential.     

Organo-chlorine pesticide (DDT and HCH) residues in the Taihu Lake Region and its movement in soil-water system I. Field survey of DDT and HCH residues in ecosystem of the region

The use of organo-chlorine (DDT and HCH) has been banned in China for 20 years. A field survey was carried out during 1999-2000 in the Taihu Lake Region. Organo-chlorine pesticide (OCP) residues in soil, water, fish and sediment samples were investigated. DDT was detected in 5 out of 10 samples with concentration ranging from 0.3 to 5.3 microg/kg in the surface (0-15 cm) layer, 6 out of 10 with 0.5 to 4.0 microg/kg in the subsoil layer (16-30 cm), and 4 of 10 with 0 to 2.7 microg/ kg in the deep soil layer (31-50 cm). Results for HCH residues in soil samples were similar to those of DDT. These results indicate that OCP residues in 0-50 cm profile had been leached out or degraded to safe level. In river water DDT was detected in 10 out of 13 samples ranging from 0.2 to 9.3 microg/l, with an average of 1.0 microg/l. While HCH was detected in 12 out of 13 samples ranging from 0.02 to 36.1 microg/l, with an average 5.6 microg/l. DDT residues in sediment ranged from 0.1 to 8.8 microg/kg, while HCH ranged from 0.3 to 66.5 microg/kg. DDT residues in fish body ranged from 3.7 to 23.5 microg/kg and HCH ranged from 3.7 to 132 microg/kg. These results demonstrate an accumulation through food chain (from soil-water-sediment-microbes-crop-fish-... etc.), also that HCH residues are generally more persistent than DDT residues. However, all these data are well below than the state warning standard limit.     

Sorption and predicted mobility of herbicides in Baltic soils

This study was undertaken to determine sorption coefficients of eight herbicides (alachlor, amitrole, atrazine, simazine, dicamba, imazamox, imazethapyr, and pendimethalin) to seven agricultural soils from sites throughout Lithuania. The measured sorption coefficients were used to predict the susceptibility of these herbicides to leach to groundwater. Soil-water partitioning coefficients were measured in batch equilibrium studies using radiolabeled herbicides. In most soils, sorption followed the general trend pendimethalin > alachlor > atrazine approximately amitrole approximately simazine > imazethapyr > imazamox > dicamba, consistent with the trends in hydrophobicity (log K(ow)) except in the case of amitrole. For several herbicides, sorption coefficients and calculated retardation factors were lowest (predicted to be most susceptible to leaching) in a soil of intermediate organic carbon content and sand content. Calculated herbicide retardation factors were high for soils with high organic carbon contents. Estimated leaching times under saturated conditions, assuming no herbicide degradation and no preferential water flow, were more strongly affected by soil textural effects on predicted water flow than by herbicide sorption effects. All herbicides were predicted to be slowest to leach in soils with high clay and low sand contents, and fastest to leach in soils with high sand content and low organic matter content. Herbicide management is important to the continued increase in agricultural production and profitability in the Baltic region, and these results will be useful in identifying critical areas requiring improved management practices to reduce water contamination by pesticides.     

Abbauverhalten von triadimefon und seinem metaboliten triadimenol in einer weizenmonokultur

Summary

In a 4‐year study, the behaviour of the residues of triadimefon and its metabolite triadimenol in different plant parts of winter wheat and in soil was investigated. The fungicide Bayleton DF (triadimefon + captafol) was applied at the beginning of earing. Triadimefon residues were quickly degraded in the great majority of the examined samples (more than 90% within the first 2 weeks after application in all aerial parts of the plant). Triadimenol residues were considerably more persistent. No residues either of triadimefon or triadimenol were found in grain at harvest time (detection limit 0.01 mg/kg).