SOIL-WATER CONSERVATION AND WINTER-WHEAT YIELD IN 3 FALLOW SYSTEMS

Interest in chemical or chemical plus tillage fallow systems has increased dramatically in Wyoming during the last 10 years. However, little information is available on their effects on available soil water or subsequent winter wheat (Triticum aestivum L.) production. Research was initiated at two locations to determine available soil water from May to October, grain yield, grain protein, and crop residue at planting with three fallow systems. Available soil water contents were highest in late May or early june and then declined until early September, regardless of fallow system. These declines in soil water content resulted because evapotranspiration exceeded precipitation. Chemical and chemical-plus tillage fallow systems resulted in similar amounts of total available soil water as conventional tillage following. Grain yields did not differ among fallow systems at Archer; while at Chugwater conventional tillage was the highest yielding one out of two years. Surface cover was greatest on the chemical fallow plots, however it was not sufficient to reduce evapotranspiration and increase soil water content.