Over‐seeded cool‐season annuals for cover crop or forage roles in warm‐season perennial grass pastures

Abstract Over‐seeded annual grasses and legumes, which can provide forage on dormant perennial warm‐season grass pastures, serve as cover crops on fallow cropland. Although erosion control is not a typical need for pastures with perennial grass sod, cover crops functioning as catch crops to reduce cool‐season nutrient loss or legumes for N fixation could contribute to reduced‐cost warm‐season pasture growth. Treatments of over‐seeded cool‐season species and management evaluating effects of cover crop removal as forage versus mulched as a N source were evaluated at three locations in 3 years. Cool‐season legumes produced more biomass N than cool‐season grasses, indicating biological N contributions of the legumes. Nitrogen limitation of the less productive, non‐fertilized grasses indicates that readily available soil N had been depleted, limiting N leaching. Despite mulching of legume biomass with N amounts of 45–89 kg ha −1 , biomass production of bermudagrass [Cynodon dactylon (L) Pers.] in the following growing season was not increased. Lack of benefit of cover crop N contributions to subsequent bermudagrass forage production indicates that the availability of increased soil N was not synchronized with periods of efficient bermudagrass N uptake. These unanticipated results appear to be due to the effect of N mineralization‐immobilization processes on N availability combined with variable rates of bermudagrass growth in response to periodic moisture limitations in this warm, humid, but uncertain environment.