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This article in AJ

  1. Vol. 101 No. 2, p. 269-277
     
    Received: May 16, 2008
    Published: Mar, 2009


    * Corresponding author(s): pkyveryga@iasoybeans.com
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doi:10.2134/agronj2008.0168

Characterizing and Classifying Variability in Corn Yield Response to Nitrogen Fertilization on Subfield and Field Scales

  1. P. M. Kyveryga *a,
  2. A. M. Blackmerb and
  3. J. Zhangc
  1. a On-Farm Network, Iowa Soybean Association, 4554 114th Street, Urbandale, IA 50322
    b Dep. of. Agronomy, Iowa State Univ., Ames, IA 50011
    c Statistical Consulting Center, Wright State Univ., 130 MM Bldg., 3640 Colonel Glenn HWY, Dayton, OH 45435

Abstract

Marked spatial and temporal variability in yield response to N fertilizer observed in individual yield response trials creates a high degree of uncertainty when estimating economic optimum rates (EORs) of N for a group of trials and when extrapolating these rates from one location to another. A survey was conducted to characterize and classify variability in yield response to N on subfield and field scales. Fertilizer N was applied at five rates (56, 84, 112, 140, and 168 kg N ha−1) in many (6–12) replicated strips within three 18- to 24-ha no-till fields during two corn (Zea mays L.) growing seasons. Yield responses or yield differences between two adjacent strips were measured in 22 to 25 grid cells ha−1 within each field. Cumulative probability distributions (CPDs) were used to estimate the probability that a given N rate produces a yield response less or equal to a specified quantity. The yield responses were classified into potential categories with different N fertilizer requirements using apparent soil electrical conductivity (ECa), digital soil map units, and relative elevation. Analysis indicated that the classifications explained <3% variability in yield response to N applied in the near-optimal range, where probabilities of receiving positive and negative marginal returns were the same. Presenting probabilities of yield response observed at different ranges of N fertilization may provide the basis for assessing the uncertainty associated with the variable effects of weather and variable supply of N when assessing economic risk and benefits of N fertilization in large-scale on-farm studies.

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