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This article in JEQ

  1. Vol. 42 No. 5, p. 1555-1564
    Received: Mar 01, 2013
    Published: June 25, 2014

    * Corresponding author(s): haajwa@ucdavis.edu
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Water and Methyl Isothiocyanate Distribution in Soil after Drip Fumigation

  1. Shad D. Nelsona,
  2. Husein A. Ajwa *b,
  3. Tom Troutc,
  4. Mary Strombergerd,
  5. Scott R. Yatese and
  6. Shankar Sharmab
  1. a Dep. of Agronomy & Resource Sciences, Texas A&M Univ.-Kingsville, MSC 228, Kingsville, TX 78363
    b Dep. of Plant Sciences, Univ. of California-Davis, 1636 E. Alisal St., Salinas, CA 93905
    c USDA–ARS, Water Management Research Unit, Fort Collins, CO 80526-8119
    d Dep. of Soil and Crop Sciences, Colorado State Univ., C127 Plant Sciences Bldg., Ft. Collins, CO 80523
    e USDA–ARS, U.S. Salinity Lab., Riverside, CA 92507


Methyl isothiocyanate (MITC) generators, such as metam sodium (Met-Na), are used for soil fumigation of agricultural land. The ban on the fumigant methyl bromide has resulted in greater use of MITC generators. To understand the efficacy of MITC, it is necessary to assess its generation and disappearance kinetics when Met-Na is applied to soil. This study evaluated the movement of water and distribution and dissipation of MITC in soil after application of Met-Na through surface drip irrigation systems. The effects of varying water application volume (25, 50, and 75 mm) and rate (1.9, 5.0, and 7.5 L h−1 m−1) were evaluated in a sandy loam soil. Good fumigant distribution within the sandy loam soil was observed under medium water application amount (50 mm) with slow to intermediate drip application rates (1.9–5.0 L h−1 m−1). Low water application amount (25 mm) or high application rate (7.5 L h−1 m−1) did not provide adequate MITC distribution throughout the soil bed width and rooting depth. Dissipation patterns of MITC in soil in all water application amounts and rates followed first-order kinetics, with a rate constant of 0.025 ± 0.004 h−1 and a half-life of 27 ± 3 h. Simulated water distribution through the soil profile using HYDRUS 2D/3D fitted measured field data well, and the model accurately simulated MITC fumigant distribution in the soil.

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Copyright © 2013. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.