Effect of Crop Residue Management and Tillage on Water Use Efficiency and Yield of Winter Wheat 1

Direct drilling of winter wheat ( Triticum aestivum L.) into surface cereal residues reduces soil erosion but frequently has resulted in stunted plants and lower grain yields than conventional planting methods. Phytotoxins produced during decomposition of surface crop residues have been implicated as the cause of these reduced yields. Field plots were established on spring and winter wheat stubble to compare plant stands, water storage, grain yields, and water‐use efficiency between direct drill seeded and conventionally seeded winter wheat. Residue management treatments included: standing stubble, complete residue removal, moving the crop residue from the seed row, and residue incorporation. New sites were used each year with the spring and winter wheat stubble maintained on Naff silt loam (fine‐silty, mixed, mesic Ultic Argixerolls) and Palouse silt loam (finesilty, mixed, mesic pachic Ultic Haploxerolls), respectively. Water soluble phytotoxins from the surface crop residues were not found during the 3‐year study. Furthermore, moving the crop residues from the seed row did not affect yields, but did alleviate the high crown node set which in turn reduced visual injury from soil active herbicides. Surface crop residues significantly improved water storage during the one season with a major runoff event, which increased grain yields and water use efficiencies, but had no effect when soil profiles were filled by spring. During the 3‐year study, winter wheat yields from plots direct drilled into surface cereal residues were equal to those from plots tilled and seeded conventionally.