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This article in SSSAJ

  1. Vol. 70 No. 3, p. 909-919
     
    Received: July 11, 2005
    Published: May, 2006


    * Corresponding author(s): griffits@onid.orst.edu
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doi:10.2136/sssaj2005.0223

Fate of Nitrogen-15 in a Perennial Ryegrass Seed Field and Herbaceous Riparian Area

  1. J. H. Davisa,
  2. S. M. Griffith *b,
  3. W. R. Horwathc,
  4. J. J. Steinerd and
  5. D. D. Myrolde
  1. a USDA–ARS, Corvallis, OR 97331
    b USDA-ARS, NFSPRC, Corvallis, OR 97331
    c Plant and Environmental Sci., Univ. of California, Davis, CA 95616-8627
    d USDA-ARS, National Program Staff, Beltsville, MD 20705
    e Crop and Soil Sci., Oregon State Univ., Corvallis, OR 97331-7306

Abstract

Intensive management of grass seed fields in the poorly drained soils of the Willamette Valley, Oregon, has prompted concern in the capacity of these landscapes and their associated minimally managed riparian areas to process and retain fertilizer N. Our goal was to determine the extent of N losses and effectiveness of a riparian area and an adjacent perennial ryegrass seed field to retain N. The fate of fertilizer 15NH4 and 15NO3 was determined with a 15N tracer experiment. During the second year of the study, 15N recovery in the plant and soil (0–30 cm) from the cropping system was 51% for 15NH4 and 43% for 15NO3 whereas recovery in the riparian area was only 20% of 15NH4 and 31% of 15NO3 Greater cropping system retention of 15N resulted from both greater uptake by the crop and greater retention of 15N in the soil. Low recovery of 15N in the riparian area was possibly the result of two significant spring flood events saturating the surface soil of the riparian area but not the cropping system. The prolonged seasonal saturated conditions significantly reduced riparian plant biomass production and N uptake and increased the potential of N loss through overland flow and denitrification. Results indicate that the cropping system had larger available N pools and a larger potential to retain fertilizer N than the riparian zone. However, both areas were prone to substantial loss of applied N.

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