Field Tests on Biochar to Reduce Emissions from Soil Fumigation.

Soil fumigation continues to be one of the most important strategies for pest management in orchards. Although low permeability tarp such as totally impermeable film (TIF) has shown to be the most effective in reducing fumigant emissions, costs are high and tarp disposal is needed after use. The objective of this study was to evaluate if soil amendment with biochar can facilitate emission reduction.  A field trial was conducted in an almond orchard with a sandy loam soil that was to be replanted back to almonds. Two amendment rates (20 and 40 ton/ha) of biochar (Cool Terra^TM) were compared to TIF for emission reduction potential following shank injection of Telone® C35 (35% chloropicrin, 63% 1,3-dichloropropene). The fumigant was applied to 66 cm soil depth at 405 kg ha^-1. Fumigant emission and distribution in soil profile were monitored. The TIF tarped plots gave the lowest emission rates only for the first five days following fumigant application. Biochar at 40 ton/ha with deep injection at 2/3 fumigant rate gave the lowest emission rates throughout a 30-d monitoring period, suggesting a great potential to use biochar as a mitigation strategy. More field tests are needed to determine more effective materials and rates of biochar towards adoption of the practice and determining the feasibility for use in orchards.