The effects of a single intense March grazing by sheep, on the components of biomass yield in 'Yamhill' soft white winter wheat (Triticum aestivum) were evaluated in Oregon during the 1979 to 1981 harvest years. Grazing increased total plant biomass yield each year. Grazing had little impact on the date of grain maturity. Differences in total grain yield between grazed and ungrazed plots reflected an increased number of seeds per head on grazed plots. Grazed plants produced an average of six more seeds per head than did ungrazed plants, an increase of 16%. Increased seed production per head resulted from a larger number of spikelets produced per head rather than from increased set of seed per spikelet. Tiller number, heads per square meter, plants per square meter, and heads per plant were not affected by grazing. The authors believe that the effects of spring grazing on the component of wheat yield in this study are related to both phenological state of the plant at grazing and to the growing conditions following defoliation.
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