Residue Management Increases Fallow Water Conservation and Yield of Deficit Irrigated Crops Grown in Rotation with Wheat.

No-tillage (NT) residue management provides cover to increase precipitation capture compared with disk tillage (DT) or in the absence of a cover crop. Therefore, NT has the potential to reduce irrigation withdrawals from the declining Ogallala Aquifer. In a 4-year study, we quantified DT and NT effects on water conservation during fallow and the subsequent yield of deficit irrigated corn (Zea mays L.) or cotton (Gossypium hirsutum L.) grown in rotation with wheat (Triticum aestivum L.). On a Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll) at the USDA-ARS Conservation and Production Research Laboratory, Bushland, TX (35.183° N, 102.1° W), blocks of cotton and corn were seeded in 0.76 m rows at 12 and 9 plants m^-2, respectively, after a 10-month fallow. To mimic limited well capacities of the region, crops were irrigated 25 or 50 mm every 10 days using a lateral move sprinkler system with mid-elevation nozzles. Soil water stored during fallow with NT residue was ~50 mm greater than for bare DT soil. Evapotranspiration (ET) increased with increasing irrigation for both crops, but only the shorter cotton crop realized consistently greater ET with NT, which retained residue. NT residue management increased mean corn yield compared with DT by 1.25 Mg ha^-1 or 86% greater at the 2.5 mm d^-1 irrigation rate and 25% from 3.86 to 4.82 Mg ha^-1 greater for the 5.0 mm d^-1 irrigation rate. Cotton lint yields did not vary by irrigation rate, but NT increased 4-year mean lint yield 0.35 Mg ha^-1 or nearly 40% greater than DT. We conclude that NT residue management increased soil water storage during fallow compared with DT. The greater corn and cotton yield with NT residue management was attributed to increased crop transpiration and less soil water evaporation.