Soil Chamber Method for Determination of Drip-Applied Fumigant Behavior in Bed-Furrow Agriculture: Application to Chloropicrin

Authors: Ashworth, Daniel; ERNST, FRED - UC RIVERSIDE; Yates, Scott

Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/28/2008
Publication Date: 5/14/2008
Citation: Ashworth, D.J., Ernst, F.F., Yates, S.R. 2008. Soil Chamber Method for Determination of Drip-Applied Fumigant Behavior in Bed-Furrow Agriculture: Application to Chloropicrin. Environmental Science and Technology. Vol 42:4434-4439

Interpretive Summary: Fumigant pesticides allow growers of high cash crops, such as strawberries and carrots, to maximize their economic return due to high crop yield. However, because such fumigants are gaseous in nature, they are easily lost from soil to the atmosphere where they negatively impact air quality. Commonly, growers use a bed-furrow production system that includes drip application of the fumigant pesticide and a covering of the bed surface with a plastic tarp (in an attempt to reduce emissions). There is a need to quantify the extent of these emissions. Unfortunately, undertaking this work in the field is expensive and time consuming. Therefore, this work aimed to design a laboratory system to test such strategies and carry out preliminary quantification of the emissions of the soil fumigant chloropicrin. As far as possible, field conditions were maintained in the experiments. The data showed very good reproducibility between replicates allowing confidence in the experimental design. High total emissions of around 60 % (of the total added) were observed in the absence of any emission reduction strategy. When the soil beds were covered with plastic tarps, emissions were reduced to around 40 %, due to an observed accumulation of chloropicrin gas below the tarp. The use of potassium thiosulfate, shown previously to reduce fumigant emissions by increasing their degradation within the soil, in the furrow had no effect on overall emissions due to the low level of emissions from this region. The reported approach offers an inexpensive alternative to studying fumigant emissions from bed-furrow systems in the field, and suggests that more highly impermeable tarps would be required to drastically reduce emissions.

Technical Abstract: To overcome the environmental impacts of soil fumigant use, emission reduction strategies, such as tarping, can be adopted by growers. There is a need to experimentally quantify the effectiveness of such strategies, preferably in a low-cost manner. In this paper we report the design and initial testing of a laboratory soil chamber approach for quantifying the soil distribution and emissions of fumigants from bed-furrow agricultural systems. As far as possible, field conditions were maintained in the experiments. In studying the drip application of chloropicrin using this system, very good data reproducibility was observed between replicates allowing confidence in the experimental design. High total emissions of around 60 % (of the total added) were observed due to the near-surface (5 cm soil depth) application. When the soil beds were tarped using high density polyethylene (HDPE) or semi-impermeable film (SIF), emissions were reduced to around 40 %, due to an observed accumulation of chloropicrin gas below the tarp. The use of potassium thiosulfate (KTS) in the furrow had no effect on overall emissions due to the low importance of this region in terms of emissions. The reported approach offers an inexpensive alternative to studying fumigant emissions from bed-furrow systems in the field, and suggests that more highly impermeable tarps would be required to drastically reduce emissions.