Atmospheric flux of agricultural fumigants from raised-bed,plastic-mulch crop production systems

Atmospheric emission of methyl isothiocyanate (MITC), chloropicrin (CP), 1,3-dichloropropene (1,3-D), and dimethyl disulfide (DMDS) were measured in the field under fumigant application scenarios representative of raised bed–plastic-mulched crop production systems. For three fumigation sites located in Florida, cumulative emissions of 1,3-D, MITC and CP were less than 11%, 6% and 2%, respectively. For three fumigation sites in located in Georgia, cumulative emissions of MITC and CP were <13% and 12%, respectively while DMDS emissions varied from 37% to 95%. In the Florida sites, emission peak flux of CP occurred within the first 6 h after application. Peak emission of 1,3-D and MITC occurred between 100 and 144 h after application. In the Georgia sites where fumigated soil was covered by low density polyethylene (LDPE) plastic, emission peak flux of DMDS and MITC occurred between 12and 48 h after application. Key factors affecting atmospheric emissions were soil moisture, soil tilth and the resistance to fumigant diffusion of the plastic film used to cover soil following application. This study demonstrated reduced atmospheric emissions of agricultural fumigants under commercial production conditions when applied using good agricultural practices including soil water contents above field capacity, uniform soil tilth in the fumigation zone and the use of metalized or virtually impermeable films to further reduce fumigant emissions. The results of this study show a need for regional flux studies due to the various interactions of soil and climate with local agricultural land management practices.     

Relative effect of soil moisture on emissions and distribution of 1,3-dichloro-propene and chloropicrin in soil columns

Emissions of soil fumigants are regulated to protect air quality in California. Irrigation prior to fumigation can reduce fumigant emissions at relatively low costs; however, the optimum range of soil water content that reduces emissions without reducing efficacy is not clearly defined. The objective of this study was to determine the effects of soil water content [at 30, 45, 60, 75, 90 and 100% field capacity (FC)] on the emission and distribution of fumigants 1,3-dichloropropene (1,3-D) and chloropicrin (CP) in columns packed with a sandy loam soil. After injecting equal amounts of cis-1,3-D, trans-1,3-D, and CP, fumigant emissions and distribution in soil were monitored for 14 days. Emissions of all three compounds showed similar response to soil water content except that CP emissions were lower than both isomers of 1,3-D. The emission peak flux was highest and occurred earliest in the driest soil while it was reduced and delayed as soil water content increased. After the peak, emission flux decreased rapidly in the driest soil but more slowly in higher water content treatments. Initially, higher soil water content resulted in substantially lower cumulative emissions among the treatments, but as time progressed, the differences in cumulative emissions decreased or even disappeared. These trends were likely due to the effect of the closed-bottom short soil columns which allowed fumigants to only move upward and contribute to emission. Higher fumigant concentrations in the soil–gas phase were observed in high soil water content treatments, due to less emission loss and more fumigant retained in the soil.     

Effect of plastic tarps over raised-beds and potassium thiosulfate in furrows on chloropicrin emissions from drip fumigated fields

Plastic tarps are commonly used in raised bed strawberry production to minimize emissions of preplant soil fumigants and are left in place throughout the growing season as part of the standard cultural practices. Soil amendments with chemicals such as thiosulfate (S2O3(2-)) can reduce fumigant emissions. A field study was conducted near Santa Maria, CA to determine the effects of low density polyethylene (LDPE) and virtually impermeable film (VIF) over raised-beds and applying potassium thiosulfate (KTS) in furrows on reducing chloropicrin (CP) emissions from a strawberry field. Four fields (or treatments) were tested with 224 kg ha(-1) CP drip-applied threecm under the soil surface. The CP flux from bed tops and furrows and gas-phase concentrations under the tarps were monitored for five d. The CP emission flux and concentration under tarp were highest immediately following application. Diurnal temperature change affected CP concentration and emission fluxes (higher values during the day and lower at night). Slightly higher CP cumulative emission occurred using LDPE tarp (19%) compared to VIF (17%). Normalized flux (CP emission flux from the beds divided by CP concentration under the tarp) being estimated from field measurement was slightly higher for LDPE than VIF indicating different tarp permeability in the field. Because of extremely low emissions from the furrows (<0.2% of total emission loss), KTS application to furrow treatments did not show further emission reductions than non-KTS treatments. This indicates that emission reduction should focus on the tarp above raised-beds when fumigant was drip-applied near bed-surface.     

Behavior of 1,3-dichloropropene and methyl isothiocyanate in undisturbed soil columns

To develop alternatives to methyl bromide (MeBr) for soil disinfection under environmental Moroccan conditions, distribution and persistence of 1,3-dichloropropene (1,3-D) and methyl isothiocyanate (MITC) were tested in undisturbed soil columns (12 cm internal diameter, 1 m length). 1,3-D was injected at a 15 cm depth and directly followed by metam-sodium (a precursor of MITC), which was applied at the soil surface of the same column using a peristaltic pump. Concerning the distribution of these fumigants in the soil profiles, our results showed that 24 h after treatment, 1,3-D and MITC were concentrated at the 0-40 cm soil layers, and reached the deeper layers 48 h later. MITC and 1,3-D dissipation was studied and the half-life (DT50) measured were 6.5 and 8 days, respectively. Total volatilization losses reached 9% for MITC and 28% for 1,3-D. MITC and 1,3-D volatilization was found to be influence by soil water contents.The results show that by reducing volatilization, photodegradation and leaching of these fumigants a suitable alternative to MeBr use is offered.     

Effects of soil fumigants on methanotrophic activity

Negative impacts on methane (CH₄) oxidation capacity have already been observed for a variety of agronomic practices, but the effect of soil fumigation on CH₄ oxidation has not been investigated. Fumigation is a common practice in agricultural crop and nursery seedling protection. Soils from various agricultural experiment stations, forest nurseries, and a landfill were evaluated for effects of 1,3-dichloropropene (1,3-D), methyl isothiocyanate (MITC), and chloropicrin (CP) on CH₄ oxidation capacities. All three fumigants significantly reduced CH₄ oxidation rates in historically non-fumigated soils (>50%). 1,3-D enhanced CH₄ oxidation in 3 out of 5 previously fumigated soils and MITC increased CH₄ oxidation rates in all historically MITC-fumigated soils compared to controls. CP universally decreased oxidation capacity regardless of fumigation history. These results support the conclusion that CH₄ oxidation effects are fumigant specific and that prior fumigation history plays a vital role in determining the impact on CH₄ oxidizer community functionality, which may have implications on the global CH₄ cycle.     

Emissions from soil fumigation in two raised bed production systems tarped with low permeability films

Raised beds are used to produce some high-value annual fruit and vegetable crops such as strawberry in California (CA) and tomato in Florida (FL), USA. Pre-plant soil fumigation is an important tool to control soil-borne pests in the raised beds. However, fumigant emissions have detrimental environmental consequences. Field trials were conducted to evaluate emissions of 1,3-dichloropropene (1,3-D) and chloropicrin (CP) in two different production systems with raised beds covered by different tarps. In the CA trial, InLine (60.8% 1,3-D and 33.3% CP) was drip-applied at 340 kg ha⁻¹ to 5 cm deep in the beds (30 cm high and 107 cm wide) tarped with polyethylene (PE) or virtually impermeable film (VIF). In the FL trial, carbonated Telone C35 (63.4% 1,3-D and 34.7% CP) was shank-applied at 151 kg ha⁻¹ to 20 cm deep in the beds (22 cm high and 76 cm wide) tarped with totally impermeable film (TIF). Emissions from tarped beds relative to furrows were contrary between the two trials. For the CA trial, the emission was 47% of applied 1,3-D and 27% of applied CP from PE tarped beds and 31% of applied 1,3-D and 15% of applied CP from VIF tarped beds, while that from uncovered furrows was <0.4% for both chemicals in both fields. In the FL trial, only 0.1% 1,3-D was emitted from the TIF tarped beds, but 27% was measured from the uncovered furrows. Factors contributing to the differences in emissions were chiefly raised-bed configuration, tarp permeability, fumigant application method, soil properties, soil water content, and fumigant carbonation. The results indicate that strategies for emission reduction must consider the differences in agronomic production systems. Modifying raised bed configuration and fumigant application technique in coarse textured soils with TIF tarping can maximize fumigation efficiency and emission reduction.     

Effects of SO2, NO2, and O3 on population development and morphological and physiological parameters of native herb layer species in a beech forest

The native ground vegetation of a beech forest was fumigated with moderate doses of SO(2), NO(2), and O(3) in open-top chambers. The effects of fumigants on growth and above-ground development were dependent on species. The treatments caused early senescence in several of the species present. The epicuticular waxes were attacked by fumigation, which was shown by higher wettability of the leaf surfaces and by leaching of ions. Interspecific differences were observed in the responses of transpiration and photosynthesis to fumigation. Similar patterns of effects on transpiration and photosynthesis, however, were found in the same species. Carbohydrate metabolism was altered by fumigation, leading to starch accumulation in the leaves. Besides effects on higher plants, fumigations also resulted in alterations of the soil microflora. The bacteria/fungi ratio was depressed at the fumigation plots.     

Behavior of methyl isothiocyanate in soils under field conditions in Morocco

The behavior of methyl isothiocyanate (MITC), active metabolite of metam-sodium (MS), was studied under field conditions in Morocco. MS was applied through drip irrigation in: (i) uncovered soil, (ii) soil covered with transparent polyethylene, and (iii) soil covered with virtual impermeable film. Concentrations of MITC were determined at different soil depths to determine the distribution of MITC and the concentration-time product (CTP). Six hours after MS application, in a sandy soil, MITC reaches the 20-30 cm soil layer, but remains highly concentrated in the upper 10-20 cm soil layer. In a silty clay soil, MITC was concentrated in the upper 0-10 cm soil layer. The dissipation of MITC under different conditions of application was fast and complete after seven days. However, MITC dissipation time (DT(50)) was <24 h in sandy soil treated, but 63 h in silty clay soil. Under these application conditions of MS, the plastic film reduced MITC loss to the atmosphere but the plastic film quality did not affect the behavior of MITC. The use of plastic film maintained high MITC concentrations and appropriate CTP at different soil depths.     

Pesticide contamination of ground water in the United States--a review

Over 70 pesticides have been detected in ground water. Aldicarb and atrazine along with the soil fumigants EDB and DCP and DBCP have been the pesticides most frequently detected in ground water. Atrazine concentrations have been correlated with high nitrate concentrations. The triazine herbicides, simazine and cyanazine, have also been detected in ground water. The annual amount of recharge, soil type, depth of aquifer from the surface, nitrate contamination and soil pH are important field parameters in determining ground-water contamination potential by pesticides. Pesticide leaching is reduced by proper choice of crop rotation, increasing pesticide application efficiency, and integrated pest management.     

Use of composted animal manures to reduce 1,3-dichloropropene emissions

Atmospheric emission of the soil fumigant 1,3-dichloropropene (1,3-D) has been associated with the deterioration of air quality in certain fumigation areas. To minimize the environmental impacts of 1,3-D, feasible and cost-effective control strategies are in need of investigation. One approach to reduce emissions is to enhance the surface layer of a soil to degrade 1,3-D. A field study was conducted to determine the effectiveness of composted steer manure (SM) and composted chicken manure (CKM) to reduce 1,3-D emissions. SM or CKM were applied to the top 5-cm soil layer at a rate of 3.3 or 6.5 kg m(-2). An emulsified formulation of 1,3-D was applied through drip tape at 130.6 kg ha(-1) into raised beds. The drip tape was placed in the center of each bed (102 cm wide) and 15 cm below the surface. Passive flux chambers were used to measure the loss of 1,3-D for 170 h after fumigant application. Results indicated that the cumulative loss of 1,3-D was about 48% and 28% lower in SM- and CKM-amended beds, respectively, than in the unamended beds. Overall, both isomers of 1,3-D behaved similarly in all treatments. The cumulative loss of 1,3-D, however, was not significantly different between the two manure application rates for either SM or CKM. The results of this study demonstrate the feasibility of using composted animal manures to control 1,3-D emissions.     

Use of Composted Animal Manures to Reduce 1,3-Dichloropropene Emissions

Atmospheric emission of the soil fumigant 1,3-dichloropropene (1,3-D) has been associated with the deterioration of air quality in certain fumigation areas. To minimize the environmental impacts of 1,3-D, feasible and cost-effective control strategies are in need of investigation. One approach to reduce emissions is to enhance the surface layer of a soil to degrade 1,3-D. A field study was conducted to determine the effectiveness of composted steer manure (SM) and composted chicken manure (CKM) to reduce 1,3-D emissions. SM or CKM were applied to the top 5-cm soil layer at a rate of 3.3 or 6.5 kg m^?2. An emulsified formulation of 1,3-D was applied through drip tape at 130.6 kg ha^?1 into raised beds. The drip tape was placed in the center of each bed (102 cm wide) and 15 cm below the surface. Passive flux chambers were used to measure the loss of 1,3-D for 170 h after fumigant application. Results indicated that the cumulative loss of 1,3-D was about 48% and 28% lower in SM- and CKM-amended beds, respectively, than in the unamended beds. Overall, both isomers of 1,3-D behaved similarly in all treatments. The cumulative loss of 1,3-D, however, was not significantly different between the two manure application rates for either SM or CKM. The results of this study demonstrate the feasibility of using composted animal manures to control 1,3-D emissions.     

Persistence, distribution, and emission of Telone C35 injected into a Florida sandy soil as affected by moisture, organic matter, and plastic film cover

With the phase-out of methyl bromide scheduled for 2005, alternative fumigants are being sought. This study of Telone C35, a mixture of (Z)- and (E)-1,3-dichloropropene (1,3-D) with chloropicirin (CP), focuses on its emissions, distribution, and persistence in Florida sandy soil in microplots with different soil-water and organic matter carbon (C) content with and without two different plastic film mulches. The addition of CP did not affect the physical behavior of the isomers of 1,3-D. Slower subsurface dispersion and longer residence time of the mixed fumigant occurred at higher water content. An increase in the percent organic carbon in the soil led to a more rapid decrease for chloropicirin than for 1,3-dichloropene isomers. The use of a virtually impermeable film (VIF) for soil cover provided a more even distribution and longer persistence under all the conditions studied in comparison to polyethylene (PE) film cover or no cover. The conditions of near field capacity water content, low organic matter, and a virtually impermeable film cover yielded optimum conditions for the distribution, emission control, and persistence of Telone C35 in a Florida sandy soil.     

Persistence,Distribution, and Emission of Telone C35 Injected into a Florida Sandy Soil as Affected by Moisture,Organic Matter,and Plastic Film Cover

Abstract

With the phase-out of methyl bromide scheduled for 2005, alternative fumigants are being sought. This study of Telone C35, a mixture of (Z)- and (E)-1,3-dichloropropene (1,3-D) with chloropicirin (CP), focuses on its emissions, distribution, and persistence in Florida sandy soil in microplots with different soil–water and organic matter carbon (C) content with and without two different plastic film mulches. The addition of CP did not affect the physical behavior of the isomers of 1,3-D. Slower subsurface dispersion and longer residence time of the mixed fumigant occurred at higher water content. An increase in the percent organic carbon in the soil led to a more rapid decrease for chloropicirin than for 1,3-dichloropene isomers. The use of a virtually impermeable film (VIF) for soil cover provided a more even distribution and longer persistence under all the conditions studied in comparison to polyethylene (PE) film cover or no cover. The conditions of near field capacity water content, low organic matter, and a virtually impermeable film cover yielded optimum conditions for the distribution, emission control, and persistence of Telone C35 in a Florida sandy soil.     

Leaching and degradation of corn and soybean pesticides in an Oxisol of the Brazilian Cerrados

Pesticide pollution of ground and surface water is of growing concern in tropical countries. The objective of this pilot study was to evaluate the leaching potential of eight pesticides in a Brazilian Oxisol. In a field experiment near Cuiabá, Mato Grosso, atrazine, chlorpyrifos, lambda-cyhalothrin, endosulfane alpha, metolachlor, monocrotofos, simazine, and trifluraline were applied onto a Typic Haplustox. Dissipation in the topsoil, mobility within the soil profile and leaching of pesticides were studied for a period of 28 days after application. The dissipation half-life of pesticides in the topsoil ranged from 0.9 to 14 d for trifluraline and metolachlor, respectively. Dissipation curves were described by exponential functions for polar pesticides (atrazine, metolachlor, monocrotofos, simazine) and bi-exponential ones for apolar substances (chlorpyrifos, lambda-cyhalothrin, endosulfane alpha, trifluraline). Atrazine, simazine and metolachlor were moderately leached beyond 15 cm soil depth, whereas all other compounds remained within the top 15 cm of the soil. In lysimeter percolates (at 35 cm soil depth), 0.8-2.0% of the applied amounts of atrazine, simazine, and metolachlor were measured within 28 days after application. Of the other compounds less than 0.03% of the applied amounts was detected in the soil water percolates. The relative contamination potentials of pesticides, according to the lysimeter study, were ranked as follows: metolachlor > atrazine = simazine > monocrotofos > endsulfane alpha > chlorpyrifos > trifluraline > lambda-cyhalothrin. This order of the pesticides was also achieved by ranking them according to their effective sorption coefficient Ke, which is the ratio of Koc to field-dissipation half-life.     

Combined use of open-air and indoor fumigation systems to study effects of SO2 on leaching processes in Scots pine litter

Both an open-air fumigation system and a laboratory-based system were used to expose decomposing Scots pine (Pinus sylvestris L.) needles to controlled concentrations of SO(2) (arithmetic mean 相似文献   

Leaching of glyphosate and AMPA under two soil management practices in Burgundy vineyards (Vosne-Romanée, 21-France)

Some drinking water reservoirs under the vineyards of Burgundy are contaminated with herbicides. Thus the effectiveness of alternative soil management practices, such as grass cover, for reducing the leaching of glyphosate and its metabolite, AMPA, through soils was studied. The leaching of both molecules was studied in structured soil columns under outdoor conditions for 1 year. The soil was managed under two vineyard soil practices: a chemically treated bare calcosol, and a vegetated calcosol. After 680 mm of rainfall, the vegetated calcosol leachates contained lower amounts of glyphosate and AMPA (0.02% and 0.03%, respectively) than the bare calcosol leachates (0.06% and 0.15%, respectively). No glyphosate and only low amounts of AMPA (<0.01%) were extracted from the soil. Glyphosate, and to a greater extent, AMPA, leach through the soils; thus, both molecules may be potential contaminants of groundwater. However, the alternative soil management practice of grass cover could reduce groundwater contamination by the pesticide.     

Temporal changes in kerosene content and composition in field soil as a result of leaching

A field experiment was designed to determine the combined effect of leaching and natural attenuation on the redistribution dynamics of kerosene--a volatile petroleum hydrocarbon mixture (VPHM)--and of its selected individual components in the soil subsurface. Variables included the composition of contaminant spilled, the soil water content before contamination and the leaching pattern. Temporal changes in the residual kerosene concentration and composition in the soil subsurface of the experimental field during 39 days and leaching by 500 mm of irrigation water were determined to a depth of 100 cm. The main processes controlling contaminant attenuation were volatilization and redistribution with depth. Soil hydration status was found to affect the attenuation, redistribution and composition of VPHM in the porous media. An initial relative increase of n-alkanes in the subsurface compared with the total VPHM in the first leaching period was a result of the volatilization of low vapor pressure compounds. The redistribution of individual components in the soil profile during leaching was in accordance with their physico-chemical properties.     

Effects of sewage sludge amendments on pesticide sorption and leaching through undisturbed Mediterranean soils

The Gharb region in Morocco is an important agricultural zone where soils receive pesticide treatments and organic amendments to increase yields. The groundwater aquifer in the Gharb region is relatively shallow and thus vulnerable. The objective of this work was to study the influence of organic amendments on diuron, cyhalofop-butyl and procymidone leaching through undisturbed soil columns. Two soils were sampled from the Gharb region, a Dehs (sandy soil) and a R’mel (loamy clay soil). Following elution (124.5 mm), the amount of pesticide residues in the leachates of the sandy soil (0.06–0.21 %) was lower than in those of the loamy clay soil (0.20–0.36 %), which was probably due to preferential flow through the loamy clay soil. The amount of procymidone leached through the amended soil columns was greater than the control for the sandy soil only. The organic amendments did not significantly influence diuron and cyhalofop-butyl leaching in either of the soils. The application of organic amendments affected the amounts of dissolved organic matter (DOM) eluted and thus pesticide leaching as a function of soil-type. Nevertheless, in some case, the formation of pesticide-DOM complexes appeared to promote pesticide leaching, thus increasing groundwater contamination risks.     

Effects of sewage sludge amendments on pesticide sorption and leaching through undisturbed Mediterranean soils

The Gharb region in Morocco is an important agricultural zone where soils receive pesticide treatments and organic amendments to increase yields. The groundwater aquifer in the Gharb region is relatively shallow and thus vulnerable. The objective of this work was to study the influence of organic amendments on diuron, cyhalofop-butyl and procymidone leaching through undisturbed soil columns. Two soils were sampled from the Gharb region, a Dehs (sandy soil) and a R'mel (loamy clay soil). Following elution (124.5 mm), the amount of pesticide residues in the leachates of the sandy soil (0.06-0.21 %) was lower than in those of the loamy clay soil (0.20-0.36 %), which was probably due to preferential flow through the loamy clay soil. The amount of procymidone leached through the amended soil columns was greater than the control for the sandy soil only. The organic amendments did not significantly influence diuron and cyhalofop-butyl leaching in either of the soils. The application of organic amendments affected the amounts of dissolved organic matter (DOM) eluted and thus pesticide leaching as a function of soil-type. Nevertheless, in some case, the formation of pesticide-DOM complexes appeared to promote pesticide leaching, thus increasing groundwater contamination risks.     

Calibration and testing of a dynamic flow-through chamber for field determination of methyl bromide volatilization flux

Accurate emission measurement of highly volatile chemicals such as methyl bromide (MeBr) is a crucial step in assessing their potential for environmental contamination. Use of flux chambers is a simple method for measuring emission rate under field conditions. To validate the applicability of a dynamic flow-through chamber for measuring MeBr emission, we provide a complete presentation of calibration and testing of the chamber. The calibration was made under a controlled system subject to ambient temperature changes. Two field experiments were conducted to test the chamber for measuring MeBr flux under conditions similar to commercial soil fumigation practices. In both the calibration and the two field experiments, the chamber provided accurate emission estimates. The maximum mass balance error was < 10% which is comparable to the micrometerological method. Because of its simplicity, we believe this dynamic flux chamber can be used reliably in quantifying the emission dynamics of highly volatile chemicals such as MeBr.