Long‐Term Conventional and No‐Tillage Effects on Field Hydrology and Yields of a Dryland Crop Rotation

Core Ideas No‐till residue management during fallow consistently increased storage of precipitation as available soil water. The annualized storm water runoff during our 30‐yr experimental record was greater for no‐till residue management than for stubble‐mulch tillage. Sustainable semiarid dryland cropping systems are critically dependent on evaporation control to provide water for crop production that is increased through no‐till residue management. Semiarid dryland crop yields with no‐till (NT) residue management are often greater than stubble‐mulch tillage (SM) because of improved soil conditions and water conservation, but information on long‐term tillage effects on field hydrology and sustained crop production are needed. Our objective was to quantify the effects of NT and SM on stored soil water, runoff, and deep drainage through a clay loam soil in relation to crop growth and yield. Wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] were grown in paired tillage treatments using a 3‐yr wheat–sorghum–fallow (WSF) rotation from 1983 to 2013. We measured crop growth and yield factors, precipitation, runoff, and Cl concentration in variable increments to a 14.0‐m depth. Cumulative runoff during the fallow periods after wheat and sorghum averaged 57 mm for NT compared with 33 mm under SM. Annual deep drainage averaged ∼ 2 mm for SM and 14 mm for NT dryland crop production based on Cl displacement compared with no drainage below the root zone of adjacent native rangeland. Despite greater runoff and drainage, plant available soil water for the 1.8‐m profile at wheat and sorghum planting averaged 194 mm for NT compared with 166 mm for SM because of reduced evaporation. Although wheat growth and grain yield did not vary with tillage, sorghum grain yield was 17% greater under NT, averaging 3420 versus 2920 kg ha–¹ under SM. We attributed the greater sorghum yield with NT to increased crop water use.