Monitoring in large field trials to assist in regulatory decisions
Surge of emission from TIF tarp-cutting is a concern and the problem can be resolved by extending tarp-covering and/or using reduced rates. In two large field trials conducted with UC Davis, Calif. Dept. of Pesticide Regulation, Sullivan Environmental, and TriCal, emission and soil fumigant data were collected to provide growers, policy makers and regulatory agencies with critical information for assisting in the adoption of low permeable tarp technology in soil fumigation with alternatives to methyl bromide. In the 2009 Oxnard field trial (Qin et al., 2011), emission flux of 1,3-D and chloropicrin from the TIF field (2% for 1,3-D and <1% from chloropicrin of totally applied ) was substantially lower than the PE tarped field (43% for 1,3-D and 12% for chloropicrin) during the 6-d film covering period.
However, upon film-cutting, greater retention of 1,3-D in the TIF field resulted in a much higher surge of emissions compared to the PE field, which resulted in similar total emission loss that included before and after tarp-cutting between the TIF and PE tarped fields. The data indicated clearly that a longer tarp-covering period is needed to reduce the surge of emissions upon tarp-cutting. To determine the safe TIF tarp-cutting time, another large field trial was conducted in Lost Hills in 2011. In addition to ambient monitoring for 3 fields with different tarp-cutting time, emissions directly from the field ground and fumigant concentration changes under tarp and in soil profile across an 8-acre field were monitored through the 16-d tarp covering period. Surge of emissions were significantly reduced from the extending tarp covering. Soil data confirmed the role of TIF tarp in retaining fumigants and improving concentration and distribution in soil. These trials demonstrated the ability of TIF to significantly reduce fumigant peak and total emissions and determined safe tarp-cutting time for TIF.
Relevant Publications and Links: