Spring Grazing Effects on Components of Winter Wheat Yield
1987
Sharrow, S. H. | Motazedian, I.
Livestock grazing of cereal grain crops during the early portion of their growing cycle is practiced to some degree in many parts of the world. While a substantial body of literature relating grain yields to defoliation practices has been accumulated, most of this work lacks detail concerning the effects of grazing on individual components of plant yield. Reports of grazing effects on grain yield have been quite variable, ranging from substantial decreases to modest increases in grain yield. Understandably, many grain producers are confused about the exact impact that livestock grazing has on their grain crop. The effects of a single intense March-grazing by sheep, on the components of biomass yield in 'Yamhill' soft white winter wheat (Triticum aestivum L. em Thell.) were evaluated near Corvallis, OR, during the 1979-to-1981 harvest years. Grazing increased total plant biomass yield each year. The greatest increase was in the grain component, which averaged 16% greater on grazed than on ungrazed plots 'during the 3 yr of the study. Contrary to widely held opinion, grazing had no effect on the number of fertile flower heads produced by the crop. Likewise, grazing did not affect either the number of seeds produced per spikelet or the average seed weight. Increased grain yield on grazed plots largely resulted from an increased number of fertile spikelets produced per wheat head on those plots. These data suggest that components of wheat grain yield that are determined prior to tiller elongation may respond to grazing management.
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