Simulating cover crops impacts on soil water and nitrogen dynamics and silage yield in the semi-arid Southwestern United States

Efficient water management is critical to sustainable crop production in arid and semi-arid southwestern United States. A study was designed to evaluate the variations in soil water content (SWC) and nitrogen (N) dynamics within the 0–100 cm soil profile and forage maize (Zea mays L.) and sorghum (Sorghum bicolor) yields in winter cover crop integrated crop rotations in a semi-arid environment using a Root Zone Water Quality Model (RZQWM2). The cover cropping treatments were no cover crop (NCC), a mixture of grasses, brassicas, and legumes (GBL), a mixture of grasses and brassicas (GB), and a mixture of grasses and legumes (GL) under maize and sorghum silage production. The root mean square error (RMSE), index of agreement (d), and Nash-Sutcliffe model efficiency coefficient (NSE) were used to evaluate the effectiveness and efficiency of the model. The observations and simulations showed that the soil water content was greater and soil temperature was lower under cover crops than under NCC. Simulated N mineralization in maize and sorghum with cover cropping was 41.1–44.2 % and 41.9–42.3 % greater than NCC. Also, the model simulated that cover crops improved the plant N uptake by 15.4–17.3 % in maize and 13.6–14.7 % in sorghum compared to NCC. Simulated aboveground biomass yields of maize and sorghum were 8.11–24.2 % and 5.68–21.3 % greater with cover crops than with NCC. Integrating cover crops in maize and sorghum silage production systems can conserve soil water and improve N uptake, increasing silage yield under semi-arid irrigated conditions in the southwestern United States.