Effects of nitrogen, phosphorous, and potassium fertilization on rapeseed yield under freeze stress

Climate variability, particularly freeze stress, poses a substantial challenge to crop yields worldwide. This study examined the impact of early 2024 freeze stress on rapeseed yields in the Yangtze River Basin, China, and assessed yield responses to nitrogen (N), phosphorus (P), and potassium (K) fertilizer rates. Six field experiments with varying N, P, and K fertilizer rates were conducted from 2022 to 2024 at two sites. In 2023–2024, a severe freeze event caused yield losses ranging from 13.4% to 63.3%, depending on nutrient fertilizer rates and sites. The effect of N fertilization on mitigating freeze stress varied across different sites, while high P fertilizer rates were associated with a reduced yield decline under freeze stress. The K fertilizer application also decreased the yield reductions caused by the freeze stress. Freeze stress disproportionately affected yield components, particularly the number of siliques per plant. Membership function values (MFV) were used as a comprehensive indicator of yield-related traits to quantify the combined effects of freeze stress and fertilization on rapeseed yield. The optimal fertilizer rates that maximized MFV were 343 ​kg ​N ​ha−1, 118 ​kg P2O5 ​ha−1, and 166 ​kg K2O ha−1 for 2022–2023 and 239 ​kg ​N ​ha−1, 110 ​kg P2O5 ​ha−1, and 169 ​kg K2O ha−1 for 2023–2024. These results highlight the importance of balanced nutrient management in improving rapeseed resilience to freeze stress and provide practical recommendations for optimizing nutrient management in cold-prone regions.