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This article in AJ

  1. Vol. 86 No. 6, p. 1026-1032
    Received: Aug 12, 1993

    * Corresponding author(s): millerbc@wsuvml.csc.wsu.edu
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Winter Wheat Yield and Grain Protein across Varied Landscape Positions

  1. Timothy E. Fiez,
  2. Baird C. Miller  and
  3. William L. Pan
  1. Dep. of Crop and Soil Sciences, Washington State Univ., Pullman, WA 99164-6420



Winter wheat (Triticum aestivum L.) yield varies greatly among landscape positions in the Palouse region of eastern Washington, yet N fertilizer is typically applied uniformly. Varying N fertilizer rates within fields to match site-specific N requirements can increase fertilizer use efficiency; however, spatially variable N management programs are limited by their ability to predict site-specific yield potentials and the resultant N requirements. The objective of this study was to ascertain the role of yield components and soil properties in determining soft white winter wheat grain yield and protein when N application rates are varied among landscape positions. Nitrogen fertilizer (0 to 140 kg N ha−1) was fall-applied on footslope, south-backslope, shoulder, and north-backslope landscape positions at each of two farms in 1989 and in 1990. Grain yield among landscapes varied by up to 55% in 1990 and by up to .33% in 1991. Landscape position grain yields increased by 199 kg ha−1/(cm precipitation + soil water reduction) (r2 = 0.51) and by 706 kg ha−1 per 100 spikes m-2 (r2 = 0.76). Grain protein concentration among landscapes increased by 2.7 g kg−1 per each increase of 10 kg residual soil NO3−N ha−1 (r2 ~ = 0.82). The large differences in grain yield among landscape positions may justify spatially variable N application. Improved N management should favorably reduce soft white winter wheat protein concentrations by minimizing high residual N levels as well as improve net returns and reduce environmental degradation. The basis for this improved N management may be site-specific yield estimates calculated from soil water availability and spike density.

WSU Crop and Soil Sciences Dep. Paper no. 9301-37.

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