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This article in JEQ

  1. Vol. 36 No. 5, p. 1331-1337
     
    Received: Dec 19, 2006


    * Corresponding author(s): Jason.krutz@ars.usda.gov
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doi:10.2134/jeq2006.0548

Reduced Surface Runoff Losses of Metolachlor in Narrow-Row Compared to Wide-Row Soybean

  1. L. Jason Krutz *a,
  2. Clifford H. Kogerb,
  3. Martin A. Lockec and
  4. Robert W. Steinriedec
  1. a USDA-ARS, Southern Weed Science Research Unit, P.O. Box 350, Stoneville, MS 38776
    b USDA-ARS, Crop Genetics and Production Research Unit, P.O. Box 350, Stoneville, MS 38776
    c USDA-ARS, National Sedimentation Lab., P.O. Box 1157, Oxford, MS 38655

Abstract

Cultural management practices that reduce the off-site transport of herbicides applied to row crops are needed to protect surface water quality. A soybean [Glycine max (L.) Merr.] field study was conducted near Stoneville, MS on Sharkey clay to evaluate row spacing (50 cm vs. 100 cm) effects on metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(methoxy-1-methylethyl) acetamide] transport. One day after the foliar application of metolachlor to 2.03 m wide by 2.43 m long plots, 60 mm h−1 of simulated rainfall was applied until 25 min of runoff was generated per plot. The calculated mass of metolachlor intercepted by the soybean foliage was greater in narrow-row than wide-row soybean, 0.39 kg ha−1 vs. 0.23 kg ha−1, respectively. Field and laboratory studies indicated that less than 2% of the metolachlor intercepted by the soybean foliage was available for foliar wash-off 1 d after application. Antecedent soil water content at the start of the simulations was lower in narrow-row soybean. In turn, there was a 1.7-fold greater time to runoff on narrow-row plots. The greater time to runoff likely contributed to lower metolachlor concentration in runoff from narrow-row plots. Cumulative metolachlor losses were significantly greater in wide-row than narrow-row soybean, 3.7% vs. 2.2%, respectively. Findings indicate that narrow-row planting systems may reduce metolachlor runoff following a post-emergence application.

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Copyright © 2007. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyAmerican Society of Agronomy, Crop Science Society of America, and Soil Science Society of America