The Effect of Herbicide Application During the Winter on Forage Production,Animal Performance,and Grain Yield of Winter Wheat

Winter wheat (Triticum aestivum L.) is used for both forage and grain production throughout the U.S. Southern Great Plains region. Management practices to increase grain yield may affect winter forage production and as a result, animal performance. The objective of this study was to determine the effect of applying herbicides in the winter to control broad leaf weeds on winter and spring forage production, animal performance, and subsequent grain yield. Four 8-ha wheat pastures at each of two locations were established under no-till practices each fall, then randomly assigned within location to receive one of the following four treatments: 1) no winter herbicides, 2) chlorsulfuron, 3) chlorsulfuron plus metsulfuron, or 4) triasulfuron. Herbicides were applied in December (yr 1) or January (yr 2) combined with 2,4-dichlorophenoxyacetic acid (2,4-D). Stocker steers were used as grazers to determine animal performance during winter (December to March) and spring (March to May) grazing periods. Animal performance and beef production per ha were not (P>0.10) affected by the application of herbicides. Animal productivity was related to climatic conditions, which affected both the energy required by the animal for maintenance and the amount of forage produced. Winter and spring forage production was not affected (P>0.10) by herbicide application. The amount of nonwheat biomass present at grain harvest was lower (P<0.03), the harvest index was higher (P<0.01), and the number of seed head was higher (P<0.01) for herbicide-treated plots than for control plots. Among the herbicides used, triasulfuron increased the number of seed heads and grain yield. Applying herbicides to winter wheat in the winter to control broadleaf weeds did not affect forage or animal production but did increase harvest index.