TILLAGE EFFECTS ON DRYLAND WHEAT AND SORGHUM PRODUCTION IN THE SOUTHERN GREAT-PLAINS

Winter wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] are important, well-adapted grain crops for the semiarid southern Great Plains. They often are grown in rotation on dryland to reduce the risk of failure associated with annual cropping and to overcome the low precipitation-use efficiencies associated with crop-fallow systems. This study on Pullman soil (Torrertic Paleustoll) determined the effects of 12 tillage systems ranging from no-tillage (herbicides only) to sweep tillage (no herbicides) on water storage and use, crop growth, yields, and yield components for dryland wheat and sorghum grown in rotation. Tillage systems did not affect mean water storage during fallow nor mean water use by either crop. All yield, growth, and yield component factors differed among growing seasons. Wheat grain and straw yields were not affected by tillage. Mean wheat grain yield was 2.92 Mg ha-1. Mean sorghum grain yield was greatest (3.91 Mg ha-1) for the system of reduced tillage after sorghum and no-tillage after wheat, and least (3.48 Mg ha-1) for the system of reduced tillage after each crop. Sorghum stover yields were not affected by-tillage. Number of panicles harvested was greatest (233 000 ha-1) and least (212 000 ha-1) for the same treatments that resulted in the greatest and least grain yields. Sorghum seed weights and test weights were not affected by tillage. This study showed that a wide range of tillage systems is adaptable for a dryland wheat-grain sorghum cropping system for the semiarid southern Great Plains.