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ARS Home » Pacific West Area » Parlier, California » San Joaquin Valley Agricultural Sciences Center » Water Management Research » Research » Publications at this Location » Publication #158275
Title: WATER AND METHYL ISOTHIOCYANATE DISTRIBUTION IN SOIL AFTER DRIP FUMIGATION WITH METAM SODIUM.

Author
item AJWA, HUSEIN - UC DAVIS
item NELSON, S - TEXAS A&M UNIV
item Trout, Thomas

Submitted to: International Conference on Methyl Bromide Alternatives and Emissions Reductions
Publication Type: Abstract Only
Publication Acceptance Date: 9/14/2003
Publication Date: 11/3/2003
Citation: AJWA, H.A., NELSON, S.D., TROUT, T.J. WATER AND METHYL ISOTHIOCYANATE DISTRIBUTION IN SOIL AFTER DRIP FUMIGATION WITH METAM SODIUM.. INTERNATIONAL CONFERENCE ON METHYL BROMIDE ALTERNATIVES AND EMISSIONS REDUCTIONS. 2003.

Interpretive Summary: Alternative soil fumigants to methyl bromide do not distribute as readily in the soil. Application methods and soil conditions are important to their efficacy. Metam sodium degrades in the soil to a fumigant, methyl isothiocyanate (MITC). It is soluble and can be applied with irrigation water. Effective use of metam sodium has been hampered by difficulty achieving good distribution of the fumigant in the soil. This study attempted to determine the best drip irrigation application rates and amounts for application of metam sodium. Soil air concentrations of MITC were measured following drip application at 3 rates and in 3 amounts of water. The largest water amount, 75 L per square meter, produced the highest soil levels of MITC, even though the metam sodium concentration in the water was lowest. Because MITC is very volatile in the soil, the high water amount slows movement of the material through the air-filled pores and increases resident time in the soil. However, high irrigation water amounts increase costs and may result in sloughing of planting beds. The effect of application rate was not clear. Recommendation is to use at least 50 L per square meter of irrigation water and apply the fumigant and water through drip tubing appropriate for the soil.

Technical Abstract: Alternative soil fumigants to methyl bromide do not distribute as readily in the soil. Application methods and soil conditions are important to their efficacy. Metam sodium degrades in the soil to a fumigant, methyl isothiocyanate (MITC). It is soluble and can be applied with irrigation water. Effective use of metam sodium has been hampered by difficulty achieving good distribution of the fumigant in the soil. This study attempted to determine the best drip irrigation application rates and amounts for application of metam sodium. Soil air concentrations of MITC were measured following drip application at 3 rates and in 3 amounts of water. The largest water amount, 75 L per square meter, produced the highest soil levels of MITC, even though the metam sodium concentration in the water was lowest. Because MITC is very volatile in the soil, the high water amount slows movement of the material through the air-filled pores and increases resident time in the soil. However, high irrigation water amounts increase costs and may result in sloughing of planting beds. The effect of application rate was not clear. Recommendation is to use at least 50 L per square meter of irrigation water and apply the fumigant and water through drip tubing appropriate for the soil.