Cover cropping increased nitrogen use efficiency indices in silage cropping systems

Abstract Excessive and inefficient use of nitrogen (N) fertilizers in cropping systems can harm the environment, soil, and human health. Cover crops can improve soil health over time, but their impact on nitrogen use efficiency (NUE) is not fully understood. This study aimed to evaluate the indices of NUE, including N uptake by cover crops biomass, cash crop yield, and changes in soil inorganic nitrogen (N) levels at 0–80 cm with winter cover cropping of grasses + brassicas + legumes, grasses + brassicas, grasses + legumes, and a no cover crop (NCC) control in irrigated silage corn ( Zea mays L.) and silage sorghum [ Sorghum bicolor (L.) Moench] systems. Cover crop aboveground biomass N ranged between 78 and 106 kg N ha −1 , and followed a decreasing trend from the first year to the fourth year of the study (2018–2022). Silage corn and sorghum yields under cover crops were 14% and 23% greater, respectively, than under NCC. In the 2021–2022 cropping year, soil inorganic N at 0–80 cm at cover crop termination was 78%–89% less under cover crops than under NCC, but resulted in 44%–76% greater N uptake efficiency with cover crops than NCC. Cover crop‐integrated silage cropping systems scavenged soil mineral N, supplemented N to subsequent silage crops, and increased silage yield and NUE indices. Cover cropping can improve soil N retention and recycling and support increased silage production in semiarid irrigated conditions.