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This article in AJ

  1. Vol. 102 No. 1, p. 71-84
    Received: Mar 19, 2009

    * Corresponding author(s): KitchenN@missouri.edu
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Ground-Based Canopy Reflectance Sensing for Variable-Rate Nitrogen Corn Fertilization

  1. Newell R. Kitchen *a,
  2. Kenneth A. Suddutha,
  3. Scott T. Drummonda,
  4. Peter C. Scharfb,
  5. Harlan L. Palmb,
  6. Darrin F. Robertsc and
  7. Earl D. Voriesa
  1. a USDA-ARS Cropping System and Water Quality Research Unit, 243 Agric. Eng. Blg., Univ. of Missouri, Columbia, MO 65211
    b Plant Sciences Unit, Univ. of Missouri, Columbia, MO 65211
    c Dep. of Plant and Soil Sci., Mississippi State Univ., Mississippi State, MS 39762


Nitrogen available to support corn (Zea mays L.) production can be highly variable within fields. Canopy reflectance sensing for assessing crop N health has been proposed as a technology to base side-dress variable-rate N application. Objectives of this research were to evaluate the use of active-light crop-canopy reflectance sensors for assessing corn N need, and derive the N fertilizer rate that would return the maximum profit relative to a single producer-selected N application rate. A total of 16 field-scale experiments were conducted over four seasons (2004–2007) in three major soil areas. Multiple blocks of randomized N rate response plots traversed the length of the field. Each block consisted of eight treatments from 0 to 235 kg N ha−1 on 34 kg N ha−1 increments, side-dressed between the V7–V11 vegetative growth stages. Canopy sensor measurements were obtained from these blocks and adjacent N-rich reference strips at the time of side-dressing. Within fields, the range of optimal N rate varied by >100 kg N ha−1 in 13 of 16 fields. A sufficiency index (SI) calculated from the sensor readings correlated with optimal N rate, but only in 50% of the fields. As fertilizer cost increased relative to grain price, so did the value of using canopy sensors. While soil type, fertilizer cost, and corn price all affected our analysis, a modest ($25 to $50 ha−1) profit using canopy sensing was found. These results affirm that, for many fields, crop-canopy reflectance sensing has potential for improving N management over conventional single-rate applications.

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Copyright © 2010. American Society of AgronomyCopyright © 2010 by the American Society of Agronomy