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Title: EFFECT OF APPLICATION VARIABLES ON EMISSIONS AND DISTRIBUTION OF FUMIGANTS APPLIED VIA SUBSURFACE DRIP IRRIGATION

Author
item Schneider, Sharon
item Dungan, Robert - Rob
item ZHENG, WEI - UC RIVERSIDE, CA
item GUO, MINGXIN - UC RIVERSIDE, CA
item LESCH, SCOTT - UC RIVERSIDE, CA
item Yates, Scott

Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2004
Publication Date: 11/1/2004
Citation: Papiernik, S.K., Dungan, R.S., Zheng, W., Guo, M., Lesch, S.M., Yates, S.R. 2004. Effect of application variables on emissions of fumigants applied via subsurface drip irrigation. Environmental Science and Technology. 38(21):5489-5496.

Interpretive Summary: Soil fumigation is useful for controlling soil-borne pests and diseases in high-cash-value crops. Fumigants are highly volatile, and methods to reduce atmospheric emissions are required to protect human and environmental health. Application of fumigants through drip irrigation has been proposed as a means to decrease fumigant emissions, improve fumigant distribution in soil, and minimize worker exposure. These experiments were conducted to investigate the effect of the configuration of the drip system on the volatilization and distribution of fumigants in bedded systems. Results indicated that changing the drip emitter spacing and using multiple drip lines in each bed had little effect on the emissions and distribution of any fumigant. Increasing the depth of application from 15 to 30 cm decreased cumulative emissions by up to 40 percent. The decrease in emissions with increasing application depth was accompanied by a small increase in the concentration of fumigants in the soil, indicating the potential for some improvement in pest-control efficacy with deeper application. These results will be useful in developing management practices for soil fumigation that result in adequate pest-control efficacy and minimize contamination of air and water by these pesticides.

Technical Abstract: Soil fumigation is useful for controlling soil-borne pests and diseases in high-cash-value crops. Fumigants are highly volatile, and approaches to reduce atmospheric emissions are required to protect human and environmental health. Application of fumigants through drip irrigation has been proposed as a means to decrease fumigant emissions, improve fumigant distribution in soil, and minimize worker exposure. These experiments were conducted to investigate the effect of the configuration of the drip system on the volatilization and distribution of the fumigants 1,3-dichloropropene (1,3-D), propargyl bromide (PrBr), and methyl isothiocyanate (MITC) in bedded systems. Results indicated that changing the drip emitter spacing and using multiple drip lines in each bed had little effect on the emissions and distribution of any fumigant. Increasing the depth of application from 15 to 30 cm decreased cumulative emissions of 1,3-D and PrBr by <10 to 20 percent. Volatilization of MITC was reduced by ~20 to 40 percent by increasing the depth of application. Emissions were reduced due to a decrease in the flux from the bed top, and deeper injection did not change the amount of fumigant volatilized from the bed side slope and furrow. The decrease in emissions with increasing application depth was accompanied by a small increase in the concentration of fumigants in the soil, indicating the potential for some improvement in pest-control efficacy with deeper application. However, deep application of fumigants with water may result in fumigant leaching below the root zone, decreasing efficacy and increasing the potential for groundwater contamination.