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This article in AJ

  1. Vol. 96 No. 1, p. 124-134
     
    Received: Dec 5, 2002
    Published: Jan, 2004


    * Corresponding author(s): mike_flowers@ncsu.edu
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doi:10.2134/agronj2004.1240

In-Season Optimization and Site-Specific Nitrogen Management for Soft Red Winter Wheat

  1. Michael Flowers *a,
  2. Randall Weiszb,
  3. Ronnie Heinigerc,
  4. Deanna Osmondd and
  5. Carl Croziere
  1. a USDA-ARS, Air Quality–Plant Growth and Dev. Res. Unit, 3908 Inwood Rd., Raleigh, NC 27603
    b Dep. of Crop Sci., North Carolina State Univ., Box 7620, Raleigh, NC 27695-7620
    c Dep. of Crop Sci, North Carolina State Univ., Vernon James Res. and Ext. Cent., 207 Research Rd., Plymouth, NC 27692
    d Dep. of Soil Sci., North Carolina State Univ., Box 7619, Raleigh, NC 27695-7619
    e Dep. of Soil Sci., North Carolina State Univ., Vernon James Res. and Ext. Cent., 207 Research Rd., Plymouth, NC 27692

Abstract

Site-specific N management based on an in-season assessment of crop N status may offer producers increased grain yield, profitability, and spring N fertilizer use efficiency (SNUE). The goal of this study was to determine the distinct contributions of (i) in-season N rate optimization and (ii) site-specific N management. Our objective was to compare site-specific and field-specific N management with typical growers' practices to determine if site-specific N management (i) increased soft red winter wheat (Triticum aestivum L.) grain yield, (ii) reduced N inputs, (iii) increased SNUE, and (iv) reduced within-field grain yield variability. Research was conducted at eight sites in 2000, 2001, and 2002. A randomized complete block design with two or five N management systems was used at two and six sites, respectively. Site-specific management did not improve grain yield compared with field-specific management when based on the same in-season estimation of optimum N rates. At sites where site-specific or field-specific systems were compared with typical growers' practices, grain yield benefits of in-season N optimization (up to 2267 kg ha−1) were apparent. For grain yield, in-season optimization of N rate was more important than site-specific management. A large reduction in N inputs (up to 48.6%) was also attributed to in-season N rate optimization. After incorporating in-season optimization, a further reduction in N inputs (up to 19.6%) was possible through site-specific application. Site-specific N application maximized SNUE compared with either field-specific or typical growers' practices at all sites and reduced within-field grain yield variance at four sites.

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