2013 Annual Report
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.
For Objective 1b, the data from field experiments conducted in FY2012 were analyzed to provide measurements of plant pest survival under fumigant and temperature stresses. Additional laboratory experiments of pest survival are needed for comparison to the field measurements. This will be completed early in FY2014.
For Objective 1c, a comprehensive process-based mathematical model was developed to assess herbicide (i.e., diazinon) emissions to the atmosphere. The mathematical model allows simulation of the diurnal variation of pesticide volatilization as affected by soil-water content, the air-solid interface partitioning coefficient (i.e. vapor sorption), soil-water retention function and soil surface resistance processes which coupled soil-based processes to atmospheric conditions.
The model was initially tested by conducting simulations of diazinon emissions for ten successive days of drying under typical semi-arid summer conditions following application to either a loam or sand soil. Results showed that the temporal variation and magnitude of diazinon emission were strongly affected by the air-solid interface partition coefficient, soil-water content and the surface resistance function. Additional testing involved comparison of model predictions and field measurement of diazinon emissions from Yolo silt loam soil from the San Joaquin Valley. In general, the model over predicted the emission rate but was able to describe a range of observed emission patterns: (a) for wet soil, the timing of emission peaks occurred during the afternoon, (b) for dry soil, the timing of the emission peaks occurred at night. This behavior cannot be predicted using traditional pesticide emission models.
For Objective 2, a field experiment was completed and the data were analyzed to determine the effectiveness of combining soil heating and reduced application of soil fumigants for controlling soil pests and pathogens. 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.
Luo, L., Ashworth, D.J., Simunek, J., Xuan, R., Yates, S.R. 2013. Assessment of methods for methyl iodide emission reduction and pest control using a simulation model. Atmospheric Environment. 66(2013):33-40.
Ashworth, D.J., Yates, S.R., Luo, L., Xuan, R. 2012. Phase partitioning, retention kinetics, and leaching of fumigant methyl iodide in agricultural soils. Science of the Total Environment. 432:122-127.
Xuan, R., Yates, S.R., Ashworth, D.J., Luo, L. 2012. Mitigating 1,3-dichloropropene, chloropicrin, and methyl iodide emissions from fumigated soil with reactive film. Environmental Science and Technology. 46:6143-6149.
Lee, S.R., Yates, S.R., Robarge, W.P., Walker, J.T., Bradford, S.A. 2013. Synergistic ammonia losses from animal wastewater. Atmospheric Environment. 17:245-250.
Wang, D., Yates, S.R., Ernst, F.F., Knuteson, J.A. 2001. Volatilization of 1,3-dichloropropene under different application methods. Journal Of Water Air And Soil Pollution. 127:109-123.
Ashworth, D.J., Luo, L., Yates, S.R. 2013. Pesticide emissions from soil – fate and predictability. Outlooks on Pest Management. 24:4-7.
Luo, L., Yates, S.R., Ashworth, D.J., Xuan, R., Becker, O. 2013. Effect of films on 1,3-dichloropropene and chloropicrin emission, soil concentration, and root-knot nematode control in a raised bed. Journal of Agricultural and Food Chemistry. 61:2400-2406.