Location: Crops Pathology and Genetics Research
Project Number: 0500-00044-030-08-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Aug 13, 2010
End Date: Sep 30, 2012
This project is designed to provide data that will facilitate effective use of “totally impermeable” film (TIF) to reduce fumigant emissions from soil. Air and soil concentrations of fumigant will be examined and modeled spatially and temporally to formulate appropriate tarp cutting times after application of fumigants. The specific objectives are: 1) Determine the best tarp cutting time for fields fumigated with 1,3-dichloropropene and chloropicrin under TIF. 2) Determine fumigant concentration change and distribution in soil profiles down to 1 m depth under the TIF. 3) Generate data on the fumigant emissions using dynamic flux chambers. 4) Determine residual fumigant concentration in soil at the time of tarp cutting to facilitate estimation of potential VOC loss thereafter. 5)Generate the data on the permeability of the plastic film (VaporSafeTM) used in this study for the active ingredients 1,3-dichloropropene and chloropicrin.
Objective 1-accumulate fumigant emissions data from ambient air around three large fields treated by broadcast shank fumigation in Ventura County. The test system will use methods preferred by California Department of Pesticide Regulation (CDPR) for assessing potential chloropicrin and 1,3-dichloropropene emissions from field applications. Objective 2-Fumigant concentration changes and movement in soil profile will be monitored throughout the study. A total of four soil-gas sampling probes will be installed in each field: two at the shank line and two between shank lines. Objective 3-Soil samples for residual fumigants by the time of tarp-cutting will be collected for evaluation of fumigant fate. Soil water content and temperature will be measured in the soil samples to facilitate required concentration calculations. Objective 4-The mass transfer coefficient (MTC) will be determined for the TIF using the standardized method (Papiernik et al. 2001; Yates et al., 2008). This method uses static sealed cells, where fumigant vapor is spiked to one side of the film and the concentrations on both side of the film are monitored until equilibrium, or, in the case of very-low-permeability films, at least until valid regression curves can be estimated based on adequate sampling at various pre-determined intervals.