Location: Contaminant Fate and Transport Research2011 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 project objectives. Under Objective 1A, we have made significant progress in determining whether total fumigant emission estimates obtained from mathematical modeling, laboratory experiments and small field-plot experiments could be used as a surrogate for estimates from large-scale field experiments. A major goal of this research was to develop new methods for obtaining emission estimates that do not require complex, time consuming and very expensive field experimentation. The data collected, to date, indicate that mathematical modeling and laboratory experiments provide essentially the same information on total fumigant emissions as large-scale field experiments. Further research is needed to develop suitable methods to estimate short-term emission rates. For Objective 1b, experiments have been conducted to determine the survival of plant pests and diseases when exposed to various levels of soil fumigants. Other experiments have been conducted to determine survival of pests when exposed to high temperatures. A database has been created to organize the response of plant pests to chemical and temperature stresses. The survival data has been analyzed using concentration-time and temperature threshold-time approaches. For Objective 1c, an experiment has been conducted to provide quantitative information on fumigant movement (methyl iodide), emissions and pest control efficacy for a citrus nematode, a weed seed and a fungus using a 2-D laboratory chamber system. The experimental conditions were simulated using a 2-D soil diffusion model coupled to a concentration-time plant-pest mortality model. Comparing experimental and predicted pest control provided a demonstration of the accuracy and viability of this approach to obtain simultaneous pest control and fumigant emissions information. For Objective 2, an experiment was conducted to determine the effectiveness of combining soil solarization (including active solarization) and reduced application of soil fumigants (Telone Inline). This study included a bare-soil control, covering the surface with high-density polyethylene film, a thermic film or a virtually impermeable film. Fumigant application rates included the standard rate (i.e., 100% application rate); a 70% and 40% reduced application rates. Each of these treatments was replicated 3 times. The experiment was conducted in September to determine if solarization could be used after the warm summer months. Preliminary results demonstrate that soil heating coupled with reduced application rate of fumigant (70%) may be an effective method to control plant pests, especially when a virtually impermeable film is used to cover the soil beds which limits fumigant losses to the atmosphere. A future experiment will be conducted during the summer to determine if warmer conditions improve the efficacy for the non-virtually impermeable film treatments.
1. 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 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.
Luo, L., Yates, S.R., Ashworth, D.J. 2011. Predicting methyl iodide emission, soil concentration, and pest control in a two-dimensional chamber system. Journal of Environmental Quality. 40(1):109-117.