2013 Annual Report
The 2011 field trial included three large fields that were fumigated with a mixture of 40:60 1,3-D:CP at ~590 lb/acre using the same fumigant application method as in the 2009 trial. All fields were tarped with TIF immediately following fumigant injection, but with different tarp-cutting times (5, 10, and 16 days for the 2, 2, and 8 acre field size, respectively). The 2011 trial was to collect information on how TIF tarp can be safely used to avoid emission spikes following tarp-cutting. For both field trials, emission was monitored continuously with dynamic flux chamber method as well as aerodynamic modeling approach. ARS researchers were in charge of collecting data on emissions directly from the tarped field and also on soil fumigant fate and distribution or transport in soil. Collaborators were in charge of collecting data for aerodynamic modeling on emission estimates from the whole field. This project was monitored by regular site visits and regular phone calls or e-mails between ARS and the University investigators on this project.
Results from the 2009 field trial show that TIF can be extremely effective in reducing fumigant emissions compared to the PE tarp. Much higher concentrations and more uniform distribution of fumigants were observed under TIF, which can lead to improved efficacy and/or using reduced fumigant rates in comparison with the standard PE film. Upon tarp-cutting after a 6-d covering period, however, surges of emissions occurred with much higher emission rates from the TIF-tarped field than the PE-covered field. Thus, a longer waiting period for the tarp-cutting is required to reduce potential exposure risks. This research provided first-hand information on emission reduction using the TIF tarp in large field applications.
The 2011 trial data show that with a TIF tarp on the field low emission flux was continuously measured throughout 16 days of tarp-covering period with a total emission loss <10% from the tarped field and < 1% at the tarp edges. Emission flux upon tarp-cutting after 16 days of fumigant application increased, but was substantially lower than the 6 days of tarp covering determined in the 2009 field trial. Data on fumigant distribution and changes over time in soil were used by the regulatory agency, California Department of Pesticide Regulation, to develop modeling methodology for estimates of fumigant emissions under various fumigation conditions. This study demonstrated the ability of TIF to significantly reduce fumigant peak flux, decrease total emission loss, and the required longer tarp-covering periods. In 2013, results from 2009 field trial and 2011 field trial were summarized. Two manuscripts were submitted to California Agriculture and both manuscripts were accepted for publication.