Crop Response to Limited Irrigation in No-till Cropping Systems.

Declining ground water concerns in the High Plains Aquifer has been complicated by drought the last eight years. The producer’s dilemma is whether to fully irrigate fewer acres versus irrigating all acres with less water. Under limited irrigation, less water is applied than is required to meet full evapotranspiration demand and the crop will be stressed. The goal is to manage cultural practices, crop residues, soil moisture and irrigation timing so resulting water stress has less impact on yield. The research objective was to determine the yield potential of winter wheat, corn, dry edible beans and canola with 100, 200 or 300 mm of irrigation and for corn with 125, 250 and 375 mm irrigation. No-till rotations were initiated in 2005 with each crop present each year. Irrigation scheduling was based on soil moisture, ET demand and crop phenology. Yearly precipitation for 2005 to 2008 was 494, 308, 238 and 305 mm (30-year average is 390mm) which represent above average moisture to extreme drought conditions. Relative yields for the three irrigation levels were 61, 79 and 95% for wheat, 66, 83 and 96% for corn, 64, 82 and 94% for dry bean and 83, 93, and 99% for canola. Data show that even low water allocations (150 to 250 mm) in this dry climate can produce from 60%to 85% of fully irrigated yields. Production functions and yield data will be used to help producers decide how to allocate water on the basis of crop productivity and potential economic return.