Sustainable Semiarid Dryland Production in Relation to Tillage Effects on Hydrology: 1983-2013.

Semiarid dryland crop yields with no-till, NT, residue management are often greater than stubble-mulch tillage, SM, as a result of improved soil conditions or water conservation, but knowledge of long-term tillage effects on the comprehensive field hydrology and sustained crop production is needed. Our objective was to quantify the effects of SM or NT on water conservation factors including deep drainage through a Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll) and crop growth and yield. Wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] were grown using the 3-year wheat-sorghum-fallow (WSF) rotation from 1983 to 2013. We measured crop growth and yield, precipitation, runoff, and chloride (Cl) concentration to depths of 10-20m. Runoff did not reflect improved infiltration due to residue cover during fallow, with NT totaling 57 mm or significantly more than the 33 mm for SM tillage. Annual deep drainage averaged approximately 2 mm for SM and 14 mm for NT dryland crop production based on CL displacement, but native rangeland did not drain beyond the rooting depth. Despite greater runoff and drainage, available soil water for the 1.8 m profile at wheat and sorghum planting averaged 166 mm for SM compared with 194 mm for NT. Although wheat growth and grain yield did not vary with tillage, NT significantly (P<0.05) increased sorghum grain yield 17% to 3420 kg/ha over the lower 2920 kg/ha for SM tillage. We attributed the greater sorghum yield with NT to increased crop water use.