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This article in AJ

  1. Vol. 94 No. 2, p. 373-380
     

    * Corresponding author(s): villar@rectorat.udl.es
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doi:10.2134/agronj2002.3730

On-Farm Monitoring of Soil Nitrate-Nitrogen in Irrigated Cornfields in the Ebro Valley (Northeast Spain)

  1. Josep M. Villar-Mir *a,
  2. Pere Villar-Mira,
  3. Claudio O. Stockleb,
  4. Francesc Ferrera and
  5. Miquel Aranc
  1. a Dep. of Environ. and Soil Sci., Univ. of Lleida, Rovira Roure 177, 25198 Lleida, Spain
    b Dep. of Biol. Syst. Eng., Washington State Univ., Pullman, WA 99164-6420
    c Soil Fertil. and Analysis Lab., Sidamon, Lleida, Spain

Abstract

The irrigated area served by the Canal d'Urgell, a semiarid region in the Ebro Valley (northeast Spain), presents problems of ground water pollution by nitrates. Corn (Zea mays L.) is widely grown in this area, and N fertilization in corn production is the major source of N input in the area, with application rates in excess of crop requirements. In this study, we monitored several commercial cornfields for soil NO3–N levels, crop N uptake, and crop productivity over a 2-yr period to quantify the relationship among soil NO3–N, N fertilizer rates, crop N use, and N loss through leaching. Monitoring soil NO3–N profiles showed that in some fields, soil NO3–N was transported to deeper layers in the soil during the growing season. In many cases, important accumulation of NO3–N was observed at the bottom of the soil at physiological maturity, increasing the risk of winter leaching. Soil N availability, calculated as preplanting soil nitrate test + N fertilizer, was neither related to plant N uptake nor final biomass and grain yield. In some plots, the occurrence of drought during the growing season was more decisive than soil-available N in explaining crop N uptake and grain yield differences. Available N levels found in the soil were above 370 kg ha−1 in all cases. Apparently, these levels were enough to satisfy the crop N requirements to achieve yields above 11 to 12 Mg ha−1 Overall data showed that there is an excess of N in the system.

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Copyright © 2002. American Society of AgronomyPublished in Agron. J.94:373–380.