Grain yields of dryland (nonirrigated) grain sorghum [Sorghum bicolor (L.) Moench], a major crop in the southern Great Plains, more than tripled in studies at the USDA-ARS Conservation and Production Research Lab., Bushland. TSI during the period from 1939 to 1997. Our objectives were to document the yield increases that occurred and to determine factors primarily responsible for the yield increases. Factors evaluated were annual precipitation, growing-season rainfall, soil water content at planting, soil water use, growing-season evapotranspiration, and pm of record. For the report, we assembled 502 treatment-years of grain yield data from 37 studies. For the 1939-1997 period, grain yields increased about 50 kg ha(-1) annually. Yields increased 139% during the 1956-1997 period, with 46 of those percentage units resulting from use of improved hybrids, based on results of a uniformly managed 40-year study, The remaining 93 percentage units for that period were attributed to of her factors. primarily to soil water at planting. increases in soil water at planting resulted from changes in management practices with time, mainly the adoption of improved crop residue management practices after about 1970.
