Effect of Simulated Stocking Densities On Dual-Purpose Winter Wheat Growth.

Dual-purpose winter wheat growth and yield in Oklahoma are influenced by cattle stocking density and variety selection. We evaluated the effect of simulated grazing intensity on wheat canopy closure of two varieties of wheat with different growth habits (prostrate and upright).  Percent canopy closure corresponds to total leaf area. Leaf area influences the ability of wheat to recover after grazing. Canopy closure was determined using a handheld NDVI sensor and digital photography. Grazing intensity was simulated by mowing wheat to heights of approximately 3, 7.5, and 12 centimeters at approximately four week intervals. Mowing was initiated in late October, which is a typical date for initiation of grazing on wheat pasture in the Southern Great Plains. Digital photographs and NDVI measurements were taken before and after each mowing treatment. Percent coverage calculated by digital photography and NDVI measurements from the Greenseeker Sensor are closely correlated, indicating that NDVI measurements can be used as a sufficient means of determining canopy closure in winter wheat. Canopy closure for the 3 centimeter mowing height never increased above 70 percent, while the 7.5 centimeter mowing height had canopy closure as high as 79 percent. Initial results from this study indicate that canopy closure measurements can be used in a model to establish optimal cattle stocking densities for dual purpose winter wheat.