This study evaluated the effects of mixed cover crop (CC) species on biomass production, nitrogen (N) uptake, soil N dynamics, and crop performance in a rainfed corn (Zea mays L.)-soybean (Glycine max L.) and continuous corn system in eastern Nebraska from 2021 to 2023. Four treatments-cereal rye, mixture-1 (cereal rye, winter pea, and triticale), mixture-2 (barley, Kura clover, and canola), and a no-cover control-were fall-seeded each year. Due to below-average precipitation, CC establishment was poor, resulting in low biomass (<0.2 Mg ha(-1)) and modest N uptake (4.1 kg N ha(-1)). Consequently, CC species did not significantly affect spring soil nitrate (NO3-N) or ammonium (NH4-N) concentrations across crop phases. Cropping year showed a strong influence on soil NH4-N, with concentrations markedly higher in 2023 than in 2022. Cereal rye exhibited a higher residue C:N ratio and contributed to increased residual fall soil NO3-N and NH4-N in upper soil layers (0-15 cm), suggesting slow biomass decomposition and potential late-season N release. Neither crop rotation nor CC treatment significantly influenced corn or soybean yields, consistent with limited CC biomass production. Favorable weather in 2023 improved corn N uptake and yield. Corn-soybean rotation enhanced corn vigor (normalized difference vegetation index [NDVI]), and CC mixtures improved soybean NDVI over cereal rye. Grain yields correlated with NDVI but not with CC biomass or N uptake, highlighting the limitations of CCs under dryland conditions. Overall, drought-limited CC growth constrained N scavenging and yield benefits, underscoring the importance of environment-specific CC management in rainfed agroecosystems.