One-time basal application of urea blended with controlled-release urea increases cotton yield and nitrogen use efficiency by enhancing mid- to late-season soil mineral nitrogen

Abstract Background The one-time combined application of conventional urea (U) with controlled-release urea (CRU), manure (M), or nitrification inhibitors (NIs) offers sustainable nitrogen (N) management options. However, their comparative performance under equivalent N inputs remains unclear. We conducted a two-year micro-plot field experiment to evaluate their effects on cotton yield, yield stability, nitrogen use efficiency (NUE), and soil mineral nitrogen (N min ) dynamics. Treatments included a control (CK, no N) and four iso-N strategies: U (conventionally split-applied, with 40% applied basally and 60% at the first flowering), U + CRU (30% U + 70% CRU, one-time basal application), U + M (70% U + 30% M, one-time basal application), and U + NI (one-time basal application). Results Both the U + CRU and U + M treatments increased shoot biomass by 53%–155% relative to the CK treatment. The highest biomass was observed in the U + M treatment in 2020 and in the U + CRU treatment in 2021. Under heavy rainfall in 2021, U + CRU enhanced N uptake in reproductive organs by 31.9%–56.1% compared with other treatments, suggesting greater resilience to high-precipitation conditions. Although U + CRU and U + M performed similarly in 2020, U + CRU outperformed all other treatments in 2021, increasing yield by 6.7%–42.3%, largely through a higher boll number, and exhibiting greater yield stability across both years. Soil data revealed consistently higher N min from flowering to boll opening under U + CRU, consistent with increased shoot N uptake and biomass. In contrast, residual N min in the 0–0.6 m soil layer was 10.4%–24.0% lower under U + CRU across both years, indicating a reduced risk of N loss. U + CRU achieved the highest NUE in 2021, exceeding that of other treatments by 43.4%–74.6%. Conclusions Overall, at the evaluated N application rate, the one-time basal application of U with CRU (30% U + 70% CRU) synchronized N supply with crop demand, thereby improving yield and yield stability while reducing residual soil N min . This strategy represents a potential climate-resilient approach for sustainable cotton production under high-precipitation conditions.