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This article in SSSAJ

  1. Vol. 63 No. 5, p. 1237-1243
     
    Received: June 5, 1998
    Published: Sept, 1999


    * Corresponding author(s): wrr@agr.okstate.edu
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doi:10.2136/sssaj1999.6351237x

Alfalfa Yield Response to Nitrogen Applied After Each Cutting

  1. W. R. Raun *a,
  2. G. V. Johnsona,
  3. S. B. Phillipsa,
  4. W. E. Thomasona,
  5. J. L. Dennisa and
  6. D. A. Cosseya
  1.  aDep. of Plant and Soil Sciences, Oklahoma State Univ., Stillwater, OK 74078 USA

Abstract

Although alfalfa (Medicago sativa L.) usually obtains a high percentage of its required N via symbiotic N fixation, additional fertilizer N applied once in the spring can increase forage yields. However, little is known about alfalfa yield response to low N rates (<50 kg N ha−1) immediately following each cutting. Low N rates (immediately following each cutting) were evaluated for total alfalfa dry matter production on a Grant silt loam (fine-silty, mixed, thermic, Udic Argiustoll). This nonirrigated experiment was initiated on a 2-yr-old alfalfa stand where sufficient P and K had been applied. Nitrogen rates of 11, 22, and 44 kg N ha−1 were applied immediately following each cutting for 5 yr (4–5 cuttings yr−1). After 5 yr of continuous N application, no differences in soil NH4–N or NO3–N were found at depths >15 cm (0- to 240-cm sampling depth). In 1994, total alfalfa dry matter yield (sum of five harvests) increased 1.29 Mg ha−1 from a total annual N application of 110 kg N ha−1 (22 kg N ha−1 following each cutting). Total forage N decreased from the second to the fifth harvest in most years. By-harvest dry matter yield increases due to applied N were only found in late-season harvests, consistent with late-season decreased N2-fixing capacity in alfalfa documented by others.

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