Location: Water Management Research2012 Annual Report
1a. Objectives (from AD-416):
To develop efficient and cost-effective field management practices to minimize emissions of methyl bromide alternative fumigants from pre-plant soil fumigation while achieving effective pest control.
1b. Approach (from AD-416):
Field management methods that have potential to reduce fumigant emissions and improve efficacy will be tested. Methods including fumigant application (new shank design, and drip. vs. shank application), low permeable tarps, irrigation, and soil amendment with organics as well as combination of these methods will be determined for their effectiveness and feasibility. Field trials will be conducted in air-quality non-attainment areas in California including Ventura County and the San Joaquin Valley. Data on emission rates, total emission losses, distribution of fumigants in soil profile and efficacy on soil pest control will be collected. Monitored data will be summarized to identify good and effective practices that can be adopted in growers’ fields.
3. Progress Report:
This project supports objective 3 of the parent project. The primary goal of the project is to examine a new totally impermeable film (TIF), and to assist regulatory agencies in decision-making required to adopt TIF tarping technology in soil fumigation. Determination of safe tarp-cutting time, quantification of off-tarp edge emissions, and evaluation of fumigant fate and movement in soil are all critical to assist in the development of safe practices, policies, and/or regulations for using TIF to reduce emission (volatilization) of soil fumigants. This research was to collect field data that are scientifically sound and acceptable to regulatory agencies for use in development of regulations since no clear guidelines on low permeability tarps are available for use in California due to concerns stated above. A large field trial was carried out from June 4 – June 22, 2011 at Lost Hills, in Kern County, CA. Participants in this trial included ARS, UCD, state regulatory agency, industry (TriCal), and consulting firm (Sullivan Environmental). The 2011 trial was a three-field trial to determine tarp-cutting time for TIF tarping. The three fields had different tarp-cutting times: 5, 10, and 16 days post fumigation. All fields were monitored using the ambient (off-field) air monitoring method. ARS researchers measured emissions continuously and directly from the ground field and collected data on soil fumigant fate and distribution or transport in an 8-acre fumigated field as well as along tarp edge areas. Emissions measured directly from the tarped ground agreed very well with ambient monitoring that increase confidence in the field data collected. Soil fumigant data were collected to examine fumigant fate and movement in soil. All data were provided to support California Department of Pesticide Regulation modeling effort on emission predictions to assist in regulation development on TIF use in soil fumigation to protect people from exposure. In an earlier trial conducted in 2009 by the same team, the TIF showed effective emission control during 6 days of tarp covering, but with a significant surge of emissions after the tarp was cut. There was no difference in total emission loss between a TIF tarped field and a standard film tarped field. In the 2011 field trial, TIF was again proven to effectively control emissions in large field applications with significantly less emissions (reduced exposure risks) after the tarp was cut 16 days post fumigation compared to that in 2009 trial (6-day tarp duration) and the 5- or 10-day tarp duration in the same trial. Emissions measured at the tarp-edge areas decreased substantially with time and distance from the tarp edge with less than 1% emissions of total applied to the field. This study demonstrated the ability of TIF to significantly reduce fumigant emissions and illustrated safe tarp-cutting times for using TIF. In addition to presentations to stakeholders and research communities, all data collected in this study have been provided to California Department of Pesticide Regulation to assist in regulation development on the use of TIF in soil fumigation. These data help maintain the availability of soil fumigants in the short to medium term and sustain the production of high value cash crops currently dependent on soil fumigants.