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Forage sorghum (Sorghum bicolor (L.) Moench) is a suitable alternative for corn silage in water-limited environments due to its similar yield potential as corn but with less water input. Cover cropping could further improve forage sorghum yield and water productivity, making it the best alternative forage crop for arid and semi-arid regions. This two-year study evaluated the effect of fallow and cover crops on soil volumetric water content (VWC), soil water extraction, changes in soil water storage (∆S), seasonal crop evapotranspiration (ET seasonal), cropping system evapotranspiration (ET system), seasonal crop water productivity (CWP seasonal), cropping system water productivity (CWP system) and forage sorghum yield under a no-till semi-arid irrigated condition. Treatments included three winter cover crop mixtures: grasses + brassicas + legumes (GBL), grasses + brassicas (GB), grasses + legumes (GL), and a no-cover crop control (fallow), arranged in a randomized complete block design with four replications. Cover crops significantly reduced soil VWC at the beginning and up to 30 days after sorghum planting (DAP). However, at 60 DAP, the VWC was mostly similar among all treatments, and at 90 DAP, it was 17–21% higher under the cover crop treatments than fallow. The ET seasonal was 22–26% higher under cover crops than fallow during cover crop growth, but it was 12–13% greater under fallow than the cover crops during forage sorghum growth. Total soil water extraction at sorghum harvest was 8–89% higher under fallow than cover crops treatments. Averaged across years, cover crop biomass yield was 11% greater with the GBL mixture than the GB and GL mixtures. Forage sorghum yield was 23%, 32%, and 18% higher under GBL, GB, and GL cover crop mixtures, respectively, than fallow. Compared to fallow, cover crop mixtures improved sorghum CWP by 38–43%. Results indicated that forage sorghum yield and CWP under semi-arid irrigated systems could be substantially improved with winter cover cropping than leaving the land fallow. • We studied cover crop effects on soil water dynamics and forage sorghum yield. • Cover crops decreased soil water content by 26% at sorghum planting. • Cover crop increased sorghum yield by 18–32% and water content at harvest by 17–21%. • System water productivity was 50–56% greater with cover crops than with fallow. [ABSTRACT FROM AUTHOR]

Cover crops can increase crop water productivity (CWP) and succeeding crop yield. However, cover crops adoption in the Southern High Plains of USA is slow due to limited water available for crop production. This study evaluated the effects of winter cover crops on soil water dynamics, corn silage yield and nutritive values, and corn silage CWP in a semi-arid irrigated condition. Three winter cover crop mixtures: grasses + brassicas + legumes (GBL), grasses + brassicas (GB), grasses + legumes (GL), and control or no cover crop (NCC) were evaluated for soil water storage, cover crop biomass, corn silage yield, nutritive values, and crop evapotranspiration (ET), and the cover crop-corn silage system water productivity (SWP) under a no-till irrigated corn silage production system. All cover crop treatments reduced soil water storage before their termination in both years. However, water storage was higher for all cover crop treatments than for NCC during corn growth. Average CWP for corn was improved by 14–29% with cover crop mixtures over the NCC. Corn silage yield among cover crop treatments was 9–26% higher than NCC. Nutritive value components of cover crops such as non-fat carbohydrates, relative forage quality, and Ca and Mg were higher in the GBL and GL mixtures than the GB in one of the two years. This study demonstrated increased corn silage yield and water productivity with cover cropping. Cover crops mixtures with legumes could offer a high-quality alternative forage for crop-cattle integrated systems, including dairy producers in the Southern High Plains region. • Cover crop effects on soil water dynamics and water use was studied. • Soil water depleted during cover crop growth. • Cover crops improved corn yield by 9–26% and CWP for corn by 14–29%. • Cover crop mixtures with legumes produced a higher forage nutritive value. [ABSTRACT FROM AUTHOR]