Location: Contaminant Fate and Transport Research2012 Annual Report
1a. Objectives (from AD-416):
Objective 1: Measure and model mechanisms and processes that affect exchange of pesticides between soil, water, plants and air; and that improve prediction of atmospheric emissions. Objective 1a. Conduct Laboratory Experiments and Modeling Studies to Test Accuracy of Simplified Approaches for Estimating Fumigant Emissions. Objective 1b. Determine the Effect of Fumigant Exposure and Soil Temperature on Survival of Nematodes, Fungi, and Weed Seeds. Objective 1c. Develop and Test a Model to Predict Fumigant Fate and Transport and Survival of Nematodes, Fungi, and Weed Seeds after Soil Fumigation. Objective 2: Develop and test new management practices to reduce contamination while controlling plant pests in strawberry and vegetable production.
1b. Approach (from AD-416):
Research will be conducted to 1) develop and test simple, low-cost, and accurate methods to obtain fumigant emissions estimates, primarily cumulative emissions. A series of laboratory chamber experiments and mathematical simulations of fumigant fate and transport will be conducted and compared directly to data collected from several field experiments completed during the previous research project. A direct comparison will be made between the existing field measurements of cumulative emissions and the results from the planned laboratory and simulation experiments. Agreement indicates that the simplified methodology provides equivalent information. 2) Laboratory incubation experiments will be conducted to obtain information on the relationship between concentration, temperature and exposure time on several important plant pest organisms (i.e., a nematode, fungi, and weed). 3) Experiments will be conducted and a mathematical model will be used to determine if the control of plant pests can be predicted after soil fumigation based on fumigant concentration and organism mortality relationships. 4) Experiments will be conducted to test a new pest-control approach that uses recirculated irrigation water and a solar collector to increase soil heating.
3. Progress Report:
Progress was made on all research project objectives. Under objective 1A, we completed laboratory experiments measuring total emissions for selected soil fumigants and used mathematical models to compare measurements to predicted emission rates. We found that complex, time consuming, and very expensive field experimentation was not required to obtain useful estimates of total fumigant emissions appropriate for in-field conditions. The results show that fumigant simulation models, laboratory fumigation experiments, and large-scale field fumigation experiments provide essentially the same information on total fumigant emissions. For objective 1b, experiments were conducted as needed to provide survival data for use in interpreting the field and laboratory experiments. For objective 1c, a process-based mathematical model was used to assess the effects of plastic film type, application depth, bed width, and furrow treatment on emission reduction and pest control using the experimental configuration from the FY11 field study. The simulations were carried out using Hydrus-2D, modified to include various fumigant-related processes; such as temperature dependent properties of the surface tarp, tarp removal at a specified time, and different surface conditions. A comparison between the simulated and experimentally measured results was made for the period-averaged emission rates and cumulative emissions under high density polyethylene film (HDPE) and virtually impermeable film (VIF). Next, the model was extended to simulate other scenarios including different application depths (5, 10, 15, and 20 cm), bed widths (50, 100 and 150 cm), and furrow treatments (depths of buried film, and with and without a reagent). The concentration-time values were also calculated to assess pest control efficacy. These findings will be further analyzed to help in optimizing the fumigant application to maintain efficient pest control and minimizing negative environmental effects. For objective 2, The field data collected in the previous (FY11) experiment was analyzed to determine the effectiveness of combining soil heating and reduced application of soil fumigants (Telone Inline) for controlling soil pests and pathogens. Three treatments were studied: a reduced application rate (70% of standard rate) of Telone Inline was applied to raised soil beds covered with high-density polyethylene film (HDPE), thermic film (Thermic), or virtually impermeable film (VIF). The results show that the Thermic treatment had the highest emission rate and the VIF treatment the lowest (<5% of Thermic). Soil pests were best controlled using VIF film, since soil heating was similar to the other treatments and fumigant concentrations (i.e., exposure) were highest under VIF. The findings demonstrate that both the film permeability and entrapped heat synergistically affect soil organism survival and should be considered together when developing new improved fumigation methods.
1. Developing an American Society of Testing and Materials (ASTM) Standard Method for Measuring Film Permeability; The Round-Robin Study. Scientists at USDA-ARS-Riverside, California, have developed and tested a method to measure the permeability of agricultural films to fumigant gases. The method has been demonstrated and accepted by many stakeholder groups, including United States Environmental Protection Agency (USEPA), which has requested that the methodology be standardized by the ASTM. Standardization requires conducting a round-robin laboratory test to demonstrate the accuracy, reliability and robustness of the measurement method. The results show that the method performed well for both experienced and first-time film testers across a wide range of film materials and film permeability values (i.e., 4 orders of magnitude). This technology-transfer effort helps stakeholders and growers to reduce atmospheric emissions of soil fumigants and helps growers to obtain emission credits that reduce the size of buffer zones surrounding treated fields; which would increase agricultural production and profit.
2. New mathematical model accurately predicts pest control and emissions of soil fumigants to the atmosphere. The use of soil fumigants is an important component of U.S. Agriculture but fumigants have the potential to pollute the atmosphere. New methods are needed to ensure crop protection while minimizing atmospheric emissions. Experiments conducted at U.S. Salinity Laboratory by ARS scientists in Riverside, California, demonstrate that a predictive model could be used to simultaneously estimate fumigant emissions and the control of plant pest organisms in field soil. The results show that the model accurately predicted both emissions and pest control and provides a new approach to optimize fumigant applications that ensure crop protection while minimizing atmospheric emissions. This methodology could be very valuable to growers in need of tools to manage soil fumigants and plant pests.
Zheng, W., Li, X., Yates, S.R., Bradford, S.A. 2012. Anaerobic transformation kinetics and mechanism of steroid estrogenic hormones in dairy lagoon water. Environmental Science and Technology. 46(10):5471-5478.