Sustainable semiarid production of dryland and deficit irrigated forage sorghum in relation to water conservation, yield, and water productivity

Authors: Baumhardt, Roland - Louis; Johnson, Grant; Schwartz, Robert

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/8/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Annual precipitation in the western Great Plains provides from 40% to 80% of crop evapotranspiration (ET), but irrigation often provides the rest. Most irrigation water is supplied from the Ogallala aquifer that, compared with current withdrawal rates, is practically non-recharging south of Nebraska. Continued pumping of the aquifer has drawn down water tables that reduced water availability and pumping capacity, which, in turn, limits deficit irrigation and increases reliance on precipitation to meet the water demand of commonly grown corn (Zea mays L.). Where demand for forage by beef or dairy cattle is sustained, water withdrawals for late-season irrigation to produce grain may be eliminated by growing forage that is “hayed-out.” This more sustainable cropping system could also be enhanced by split pivot management with dryland forage that redirects water to maintain higher pumping capacities, but the semiarid dryland forage production reliance on precipitation is inherently riskier. Scientists from ARS-Bushland initiated a study where the objective was to compare water conservation, yield and water productivity of limited deficit irrigated and dryland forage- and grain -sorghum [Sorghum bicolor (L.) Moench] grown in the three-year wheat-sorghum-fallow (WSF) rotation with conventional or no tillage (NT). Measurements were taken for precipitation, soil water at planting and harvest, grain and biomass yield, and the forage nutrient value. Data show that less precipitation was stored as soil water with NT than SM when producing forage because of the absence of residue or the opposite result for grain crops with residue. Dryland hay, biomass, yields were about half of the grain plus residue yields, but freeze injury and hail damage destroyed two grain crops. Value of irrigated forage exceeded grain in proportion to irrigation applied. In conclusion,compared with grain, forage production may be a more sustainable alternative cropping system.