|Qin, Ruijun - UC DAVIS|
|Ajwa, Husein - UC DAVIS|
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 18, 2007
Publication Date: September 12, 2007
Citation: Qin, R., Gao, S., Hanson, B.D., Mcdonald, J.A., Trout, T.J., Ajwa, H.A. 2007. The Effect of Drip Application of Ammonium Thiosulfate on Fumigation Degradation in Soil Columns. Journal of Agricultural and Food Chemistry. 55:81 93-8199 Interpretive Summary: Tarping with low permeable films can effectively minimize fumigant emissions and improve fumigation efficacy. However, the accumulated fumigants under the tarp may present high risks to workers, bystanders and the environment when the tarps are removed or cut for planting. This research tested the effect of various rates of subsurface drip-application of ammonium thiosulfate (ATS) on the degradation of 1,3-dichloropropene and chloropicrin under low permeable tarps. Fumigant degradation in soils was accelerated with the increasing rate of ATS. The results indicate that applying ATS to soil can be used in field applications to minimize fumigation risks and benefit crop productions especially for strawberry fields with raised beds and drip-irrigation systems.
Technical Abstract: Low permeability tarps can effectively minimize fumigant emissions while improving fumigation efficacy by retaining fumigants under the tarp. However, when planting holes are cut through the tarps, high-concentration fumigants may be released and result in environmental and worker safety hazards. In a 11-d column study, we explored the effect of subsurface dripping ammonium thiosulfate (ATS) on 1,3-dichloropropene (1,3-D) and chloropicrin (CP) degradation in soil. Decrease of 1,3-D and CP concentrations in soil-gas phase followed a 3-parameter logistic equation for all treatments. It was slowest in the control with a half-life (t1/2) of 86.0 h for 1,3-D and of 16.3 for CP and most rapid when ATS was applied at 4:1 ATS:fumigant molar ratio with a half-life of 9.5 h for 1,3-D and of 5.5 h for CP. A 100% efficacy on controlling selected nematodes and weeds was achieved in all treatments. Our results indicate that applying ATS via the drip-irrigation systems to soil can accelerate fumigant degradation in soil and thus reduce emissions. This technique may be applicable in raised-bed production of strawberry where drip-application of fumigants has become common.