TILLAGE AND CROPPING SYSTEM EFFECTS ON WINTER-WHEAT AND GRAIN-SORGHUM

Grain yields of dryland winter wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] are affected by cropping system and tillage. A study was conducted at Garden City, KS, in 1989 and 1990 to determine the effect of cropping system and tillage on soil water, yield components, and grain yield of these crops. Cropping systems compared were wheat-fallow (WF), sorghum-fallow (SF), wheat-sorghum-fallow (WSF), continuous sorghum (SS), and continuous wheat (WW). Conventional (CT) and no-tillage (NT) were compared in all but the SF and SS systems, which were CT. Wheat-fallow and WSF yielded more than WW in both years and WF yielded more than WSF in 1989. No-tillage increased the yield of WF and WSF in 1989, but cold temperatures reduced the number of spikes per square foot and yield of WSF-NT in 1990. Tillage did not affect WW yields. Sorghum-fallow and WSF yielded more than SS in both years. Sorghum-fallow yielded less than WSF in 1989 because of lack of maturity before frost. Tillage did not affect WSF yield. Yield increases of both crops were often accompanied by improved water-use-efficiencies. Yield components most responsible for variations in yield were the number of spikes per square foot and kernels per spike for wheat, and the number of kernels per panicle and kernel weight for grain sorghum. Soil water at wheat planting affected spikes per square foot in both years and kernels per spike and yield in 1989. Soil water at sorghum planting affected kernels per panicle, kernel weight, and yield in 1990. Thus, water-conserving practices, such as fallow and no-tillage, improve water storage and use, resulting in increases in yield components and grain yield of grain sorghum and wheat.