Exploring the potential of warm‐season cover crops and nitrogen management for improving corn yield and water use efficiency

Corn ( Zea mays L .) in the United States is predominantly grown as a single crop each year, with fields often left fallow after crop harvest, contributing to soil degradation, erosion, and nutrient loss. Winter cover crops (CCs) are widely promoted to address these issues; however, their effectiveness in the southern United States is limited by short winters and low biomass accumulation. Concerns over water use further hinder CC adoption in rainfed systems. This study evaluated the potential of warm‐season CCs as an alternative to winter CCs in central Texas, aiming to enhance CC biomass production and lengthen the interval between CC termination and corn planting. Two warm‐season CC species, sunn‐hemp ( Crotalaria juncea ) and sorghum‐sudangrass ( Sorghum × drummondii ), were tested under three residue management strategies (mulching, incorporation, and forage harvest) and three nitrogen (N) fertilization levels (0%, 50%, and 100% of recommended rate). Cumulative seasonal evapotranspiration did not differ among treatments during both the CC and the corn‐growing period, suggesting that CC water use was comparable to fallow. However, CC species and residue management significantly influenced corn yield and water use efficiency. Sunn‐hemp with retained (mulching and incorporation) residue produced the highest corn yield, while forage harvest was beneficial following sorghum‐sudangrass. Furthermore, yield trade‐off analysis showed minimal negative impact of CCs on corn yield or biomass. These findings support the integration of warm‐season CCs into rainfed corn systems. Future research should explore multispecies CC mixtures to optimize N cycling and biomass quality, enhancing both agronomic performance and environmental benefits.