Limited Irrigation for Managing Declining Water Resources in the US High Plains

The US High Plains region has a semiarid climate receiving between 330 and 455 mm of rainfall annually. In the Nebraska Panhandle of the High Plains, 30-year average rainfall is 394 mm, and one-fourth of agriculture is under irrigation. In addition to concerns about water quality, there is a growing concern over water quantity for ground- and surface-water resources that producers use for irrigation. Wisely managing limited water resources for irrigation can help maintain crop productivity and profitability. Deficit irrigation research for 13 years (2005–2017) was conducted in the Nebraska Panhandle to study effects of limited irrigation on maize (Zea mays L.) production. In this study, maize followed dry bean in a four-crop no-till rotation system: spring canola (Brassica napus) – winter wheat (Triticum aestivum L.) – dry bean (Phaseolus vulgaris) – maize. The experimental design was a randomized complete block with four replications and with irrigation levels as the main treatment. Irrigation treatment included 127, 254, and 381 mm of irrigation. This 13-year study period included a wide inter-annual variation in seasonal rainfall. Production functions showed that at the lowest irrigation level, maize yield was in average 72% of maximum yield. At the medium irrigation level, yields were 91% of maximum yield in average. Considering wet and dry years, optimal irrigation required to achieve \u3e90% relative maize yield ranged from 254 to 356 mm. This information is important for producers and regulators in making decisions concerning optimal use of limited water resources in agriculture