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This article in AJ

  1. Vol. 101 No. 4, p. 916-924
    Received: Dec 18, 2008

    * Corresponding author(s): john.schmidt@ars.usda.gov
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Nitrogen Recommendations for Corn: An On-The-Go Sensor Compared with Current Recommendation Methods

  1. John P. Schmidt *a,
  2. Adam E. Dellingerb and
  3. Doug B. Beeglec
  1. a USDA-ARS, Bldg. 3702, Curtin Rd., University Park, PA 16802
    b USDA-NRCS, 478 Jeffers St., Bldg. 3, Ste. D, Dubois, PA 15801
    c Dep. of Crop and Soil Sci., Pennsylvania State Univ., 116 ASI Bldg., University Park, PA 16802


Precision agriculture technologies provide the capability to spatially vary N fertilizer applied to corn (Zea mays L.), potentially improving N use efficiency. The focus of this study was to evaluate the potential of improving N recommendations based on crop canopy reflectance. Corn was grown at four field sites in each of 2 yr in Centre County, Pennsylvania. Preplant treatments included: zero fertilizer, 56 kg N ha−1, and manure. Split-plot treatments included the following N sidedress rates as NH4NO3: 0, 22, 45, 90, 135, 180, and 280 kg N ha−1, and one at-planting N rate of 280 kg N ha−1 Light energy reflectance (590 and 880 nm), chlorophyll meter (SPAD) measurements, and the presidedress NO3 test (PSNT) results were obtained at sidedress. The late-season stalk NO3 (LSSN) test was determined. The economic optimum nitrogen rate (EONR) was determined based on grain yield response to sidedress N rates. Relative green normalized difference vegetation index (GNDVI) and relative SPAD were based on relative measurements from the zero sidedress treatment to the 280 kg N ha−1 at-planting treatment. The EONR from 24 preplant treatment–site combinations was related to relative GNDVI (R 2 = 0.76), the PSNT (R 2 = 0.78), relative SPAD (R 2 = 0.72), and the LSSN test (R 2 = 0.64), suggesting that relative GNDVI was as good an indicator of EONR as these other, more conventional tests. Because relative GNDVI can be obtained simultaneously with a sidedress N fertilizer application, the potential to accommodate within-field spatial and season-to-season temporal variability in N availability should improve N management decisions for corn production.

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Copyright © 2009. American Society of AgronomyCopyright © 2009 by the American Society of Agronomy