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This article in AJ

  1. Vol. 105 No. 4, p. 1167-1175
     
    Received: Nov 20, 2012
    Published: May 31, 2013


    * Corresponding author(s): ellen.mallory@maine.edu
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doi:10.2134/agronj2012.0447

In-Season Nitrogen Effects on Organic Hard Red Winter Wheat Yield and Quality

  1. Ellen B. Mallory *a and
  2. Heather Darbyb
  1. a Dep. of Plant, Soil and Environ. Sciences, Univ. of Maine, 495 College Ave., Orono, ME 04473
    b Dep. of Plant and Soil Science, Univ. of Vermont, 63 Carrigan Dr., Burlington, VT 05405

Abstract

Ensuring adequate available N for grain protein development is a primary challenge for organic production of winter bread wheat (Triticum aestivum L.). Topdressing organic wheat in-season may improve grain yield and quality. The objective of this study was to determine if supplemental N topdressing at key wheat developmental stages would improve organic hard red winter wheat yield and protein concentrations. Field experiments were conducted over 4 site-years from 2009 to 2011 in Maine and Vermont, using the variety Harvard. Treatments were a factorial arrangement of two organic-approved N sources (Chilean nitrate, CN, and dehydrated poultry litter, DPL) and three times of application (tillering, flag leaf, and boot stages). Plant N uptake, grain yield, and grain protein concentration were determined. Plant-accumulated N was always higher in the CN treatments than in the DPL and manure-only treatments. The CN topdress treatments yielded on average 11% more than the manure-only treatment and 6% more than DPL treatments. Topdressing increased grain protein concentration in all cases, although none of the treatments reached the 120 g kg–1 milling standard, due in part to variety Harvard being a low-protein, high-yielding variety. Chilean nitrate was more effective at increasing grain protein levels than DPL, and for both N sources, later applications were more effective than earlier ones. Topdressing could be a cost-effective strategy to boost grain protein levels for organic winter wheat production, but further work is needed to evaluate topdressing with higher protein varieties and identify additional rapidly-available and economical organic approved N sources.

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