Integrating Winter Cover Crops Did Not Change Cotton Lint Yield Responses to Nitrogen Fertilization in Sandy Soils

A two-year field trial (2021–2023) was conducted to evaluate the impacts of cover crop (CC) inclusion (cereal rye, crimson clover, mixtures of cereal rye and crimson clover, and fallow control) and nitrogen (N) fertilization (0, 22, 45, 90, 135, and 180 kg N ha−1) in cotton production in sandy soils. Cover crops were planted in October and terminated two weeks before cotton planting in May. The N was applied in split applications. Cover crop aboveground biomass was collected, oven dried, and weighed, and then used for C and N analyses. Soils were sampled at CC termination and analyzed for biogeochemical properties. Cotton lint yields and agronomic nutrient use efficiency (aNUE) were estimated. The CC mixtures provided higher organic C and N inputs as residue returns than individual species. Integrating CCs had limited impacts on measured soil properties. Integrating CCs resulted in positive, neutral, and adverse effects on lint yield and aNUE depending on species and growing seasons. Applying N at 22 kg ha−1 increased lint yields in 2022, while higher rates did not improve the yields further. Similar patterns of impacts were observed at the N rate of 45 kg ha−1 in 2023. The results indicated that integrating CC mixtures can favor long-term C and N sequestration in sandy soils. However, optimal management is essential to realize their benefits. Relevant research to better understand the decomposition of their residues would be beneficial in improving the management of desirable outcomes.