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This article in AJ

  1. Vol. 99 No. 6, p. 1424-1435
     
    Received: Sept 11, 2006


    * Corresponding author(s): rps21@psu.edu
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doi:10.2134/agronj2006.0258

Aerial Color Infrared Photography to Optimize In-Season Nitrogen Fertilizer Recommendations in Winter Wheat

  1. Ravi P. Sripada *a,
  2. Dianne C. Farrerb,
  3. Randy Weiszc,
  4. Ronnie W. Heinigerd and
  5. Jeffrey G. Whitee
  1. a Canaan Valley Institute, USDA-ARS-PSWMRU, Bldg. 3702, Curtin Rd., University Park, PA 16802
    b NCDA&CS Agronomic Division, Greenville, NC 27858
    c Dep. of Crop Sci., North Carolina State Univ., Raleigh, NC 27695-7620
    d Dep. of Crop Sci., Vernon James Res. and Ext. Cent., 207 Research Rd., Plymouth, NC 27962
    e Dep. of Soil Sci., North Carolina State Univ., Raleigh, NC 27695-7619

Abstract

Remote sensing in the form of aerial color infrared (CIR) photography has been shown to be a useful tool for in-season N management in winter wheat (Triticum aestivum L.). The objectives of this study were (i) to develop a methodology for predicting in-season optimum fertilizer N rates for winter wheat at growth stage (GS) 30 directly from aerial CIR photography and (ii) to quantify how the relationships between these optimum N rates and spectral indices respond to different levels of biomass of the wheat crop. Field studies were conducted for three winter wheat growing seasons (2002–2004) over a wide range of soil conditions across North Carolina using a split-split plot randomized complete block design. Different planting date–seeding rate (PDSR) combinations were applied to create a range of biomass levels at GS 30. Different levels of N were applied at GS 25 (N25) to create a range of N supply and winter wheat radiance, and at GS 30 (N30) to measure grain yield response to N30 Aerial CIR photographs were obtained at each site at GS 30 before N applications. Significant biomass response to PDSR and yield response to N25 and N30 were observed. Optimum N30 ranged from 0 to 124 kg ha−1 with a mean of 55 kg ha−1 Better prediction of optimum N30 rates were obtained with spectral indices calculated relative to high-N reference strips compared to absolute bands or spectral indices. Biomass measured at GS 30 influenced the strength of the relationship between optimum N30 and spectral indices. When the GS-30 biomass was >1000 kg ha−1, the best predictor of optimum N30 (R 2 = 0.85) was a quadratic model based on measured winter wheat radiance relative to mean radiance in the G band for the high N reference strip (Rel GS).

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Copyright © 2007. American Society of AgronomyAmerican Society of Agronomy