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Effect of N Fertilizer on Protein Content of Grain, Straw, and Chaff Tissues in Soft White Winter Wheat

Glenn, D. M., Carey, A., Bolton, F. E., Vavra, M.
Agronomy journal 1985 v.77 no.2 pp. 229-232
Triticum aestivum, nitrogen fertilizers, protein composition, straw, chaff
Nitrogen management programs of soft white winter wheat (Triticum aestivum L.) in semiarid regions are generally based upon soil tests of available water and residual N levels. The purpose of this work was to develop postharvest criteria for N-sufficiency and N-insufficiency based on tissue protein levels as it relates to maximum grain yield in a fallow-wheat rotation. Yield-protein relationships in grain, straw, and chaff tissues were examined in field trials from 4 harvest years on a Walla Walla silt loam (coarse-silty, mixed, mesic, Typic Haploxeroll). Grain protein content was a better postharvest indicator of N sufficiency for maximum grain yield than straw or chaff protein levels. Excessive weed growth confounded this relationship in 1 year. Using a chi-square interaction procedure, a critical level of 8.8% grain protein was determined necessary for N sufficiency in ‘Stephens’ soft white winter wheat when weed growth was not a management problem. The transition zone between N sufficient and N insufficient responses was between 8.3 and 9.1% grain protein. The amount of relative yield lost to N insufficiency was related to grain protein content. There was a 9.8% yield reduction for each grain protein percentage below 9.1. Critical protein values indicative of N insufficiency could not be determined for straw and chaff tissues. Straw and chaff protein levels greater than 2.6 and 3.5%, respectively, were exclusively associated with N sufficiency.