Water conservation practices for a river valley irrigated with groundwater

Water conservation strategies for center pivot and furrow irrigation in the Central Platte Valley of Nebraska were evaluated using computer simulation . irrigation requirements, grain yield, return flow and net depletion (gros s irrigation minus return flow) of groundwater were simulated for a period of 29 years for Herd and Wood River sill loam soils. Grain yields were simu lated for a typical corn variety for non-limiting water supplies (maximum a ttainable yield), for two levels of deficit irrigation (irrigation limited to certain growing periods), and for dryland conditions. Additional simulat ions were performed for a short-season corn, grain sorghum, and soybeans. T he impacts of tillage practices on water conservation were also investigate d. Center pivot irrigation on the Herd silt loam required 75-125 mm/year less water application than furrow irrigation. For the Wood River silt loam, wat er applications were the same for both irrigation systems. Applied water de pths were reduced by an additional 75-125 mm using deficit irrigation with only a small reduction in yield. Return flow to the groundwater was small f or well-managed pivots but high for some furrow irrigation systems based on the assumption that all deep percolation returns to the aquifer in the Cen tral Platte Valley. Net depletion (gross irrigation minus return flow) of t he groundwater for a center pivot with LEPA was 50 mm (17%) less than a cen ter pivot with impact sprinklers. Ridge till had a net depletion 50 mm (25% ) less than conventional tillage (double disk, plant) for furrow systems. ( C) 1999 Elsevier Science B.V. All rights reserved.