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This article in JEQ

  1. Vol. 38 No. 2, p. 393-401
    OPEN ACCESS
     
    Received: June 18, 2008


    * Corresponding author(s): cvankessel@ucdavis.edu
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doi:10.2134/jeq2008.0277

Dissolved Organic Nitrogen: An Overlooked Pathway of Nitrogen Loss from Agricultural Systems?

  1. Chris van Kessel *a,
  2. Tim Cloughb and
  3. Jan Willem van Groenigenc
  1. a Dep. of Plant Sciences, Univ. of California-Davis, Davis, CA 95616
    b Soil & Physical Sciences Group, Agriculture & Life Sciences Division, Lincoln Univ., PO Box 84, Lincoln 7647, New Zealand
    c Wageningen Univ., Dep. of Soil Quality, P.O. Box 47, 6700 AA, Wageningen, the Netherlands

Abstract

Conventional wisdom postulates that leaching losses of N from agriculture systems are dominated by NO3 Although the export of dissolved organic nitrogen (DON) into the groundwater has been recognized for more than 100 yr, it is often ignored when total N budgets are constructed. Leaching of DON into stream and drinking water reservoirs leads to eutrophication and acidification, and can pose a potential risk to human health. The main objective of this review was to determine whether DON losses from agricultural systems are significant, and to what extent they pose a risk to human health and the environment. Dissolved organic N losses across agricultural systems varied widely with minimum losses of 0.3 kg DON ha−1yr−1 in a pasture to a maximum loss of 127 kg DON ha−1yr−1 in a grassland following the application of urine. The mean and median values for DON leaching losses were found to be 12.7 and 4.0 kg N ha−1yr−1, respectively. On average, DON losses accounted for 26% of the total soluble N (NO3 plus DON) losses, with a median value of 19%. With a few exceptions, DON concentrations exceeded the criteria recommendations for drinking water quality. The extent of DON losses increased with increasing precipitation/irrigation, higher total inputs of N, and increasing sand content. It is concluded that DON leaching can be an important N loss pathway from agricultural systems. Models used to simulate and predict N losses from agricultural systems should include DON losses.

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Copyright © 2009. 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