Location: Contaminant Fate and Transport ResearchTitle: Coupling of soil solarization and reduced rate fumigation: Effects on methyl iodide emissions from raised beds under field conditions Author
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2013
Publication Date: 12/5/2013
Citation: Ashworth, D.J., Yates, S.R., Luo, L., Lee, S.R., Xuan, R. 2013. Coupling of soil solarization and reduced rate fumigation: Effects on methyl iodide emissions from raised beds under field conditions. Journal of Agricultural and Food Chemistry. 61:12510-12515. Interpretive Summary: Methyl iodide is an agricultural fumigant used to kill pests in soil prior to planting crops. However, it can be emitted from the soil into the air and negatively impact air quality. One way to reduce the amount of emissions is to use less methyl iodide during application but this may reduce the level of pest control. Therefore, one option is to couple the reduced rate of fumigation with a second approach that still allows for effective pest control. In this study we coupled soil solarization (heating the soil using solar energy and/or hot water) with a 70% rate methyl iodide application to determine the effect on methyl iodide emissions from soil to air. Basic solarization (covering the raised soil bed with plastic film) did not reduce emissions compared to 100% rate fumigation only (also under plastic film) because the majority of the methyl iodide moved through the soil to the furrow which is not covered by plastic film; and where it was emitted into the air. Also, the plastic film in the solarized treatment became less able to prevent methyl iodide passing through it due to its longer period of exposure. In the solarized treatment using hot water addition, the added water very effectively reduced methyl iodide emissions by blocking soil pores and thereby limiting gas diffusion. This research will help growers to meet future regulations on fumigant and VOC emissions while maintaining pest control.
Technical Abstract: Using field plots, we studied the effect on methyl iodide (MeI) emissions of coupling soil solarization (passive and active) and reduced rate fumigation (70% of a standard fumigation) in raised beds under virtually impermeable film (VIF). The results showed that for the standard fumigation and the passive solarization+fumigation treatments, emissions from the non-tarped furrow were very high (~50%). Emissions from the bed top and sidewall of these treatments were relatively low but were increased in the latter due to the longer environmental exposure of the VIF covering with the coupled approach (increased tarp permeability). Overall, this approach offered no advantage over fumigation-only in terms of emission reduction. With active solarization+fumigation, the large application of hot water during solarization apparently led to severely limited diffusion causing very low total emissions (<1%). Although this suggests a benefit in terms of air quality, a lack of diffusion could limit the pesticidal efficacy of the treatment.