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This article in AJ

  1. Vol. 98 No. 2, p. 327-338
     
    Received: May 19, 2005
    Published: Mar, 2006


    * Corresponding author(s): jeff_white@ncsu.edu
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doi:10.2134/agronj2005.0154

Remote Sensing-Informed Variable-Rate Nitrogen Management of Wheat and Corn

  1. Nan Honga,
  2. Jeffrey G. White *b,
  3. Randy Weiszc,
  4. Carl R. Crozierb,
  5. Marcia L. Gumpertzd and
  6. D. Keith Casselb
  1. a Dep. of Agron., 209A Waters Hall, Univ. of Missouri, Columbia, MO 65211
    b Dep. of Soil Science, North Carolina State Univ., Raleigh, NC 27695-7619
    c Dep. of Crop Science, North Carolina State Univ., Raleigh, NC 27695-7620
    d Dep. of Statistics, North Carolina State Univ., Raleigh, NC 27695-8203

Abstract

In-season, site-specific, variable-rate (SS) N management based on remote sensing (RS) may reduce N losses to groundwater while maintaining or increasing yield and N fertilizer-use efficiency. We compared in-season, RS-informed N management applied on a uniform, field-average (FA) or SS basis with the current uniform best management practice (BMP) based on “Realistic Yield Expectations” (RYE) in a typical 2-yr southeastern U.S. coastal plain rotation: winter wheat (Triticum aestivum L.)–double-crop soybean [Glycine max (L.) Merr.]–corn (Zea mays L.). Compared with the RYE-based BMP, RS-informed SS management achieved: (i) a maximum of 2.3 mg L−1 less groundwater NO3–N after 2001 wheat due to 39 kg ha−1 less fertilizer N and a 25% greater harvest N ratio (N in grain or forage/total N applied); (ii) 370 kg ha−1 more 2002 corn grain with 32 kg ha−1 greater N applied, similar harvest N ratio, and 37 kg ha−1 greater surplus N; (iii) 670 kg ha−1 more 2003 wheat grain associated with 14 kg ha−1 greater fertilizer N, 27% greater harvest N ratio, and 9 kg ha−1 less surplus N. Excepting one corn FA treatment that received excessive N, RS-informed management produced equal or greater economic returns to N than RYE, and less surplus N for wheat. Treatments produced enduring effects on groundwater [NO3–N] consistent with agronomic results, but small relative to temporal [NO3–N] fluctuations that were positively correlated with water table elevation. To assess N management in leaching-prone soils, frequent, periodic groundwater monitoring during and after the cropping season appears essential.

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