Optimization of water and fertilizer regime for greenhouse radish using BBD response surface method coupled with NSGA-II algorithm.

Objective: To address the issue of yield-quality imbalance caused by the low water-fertilizer synergy efficiency of white radish in greenhouses in the cold region of northern Xinjiang, this study aimed to reveal the seasonal specific interaction mechanisms of irrigation amount (W), nitrogen application rate (N), and potassium application rate (K), and to construct a multi-objective optimized water-fertilizer management model. Methods: Experiments were conducted in summer and winter based on the Box - Behnken design. The interaction effects of water and fertilizers were analyzed through the response surface model, and the multi - objective collaborative optimization of yield, soluble sugar, and vitamin C was achieved by combining with the NSGA - II algorithm. Results: There were significant seasonal differences. In summer, the available potassium concentration in the 10 - cm soil layer (206.98 mg/kg) under the W2K1N2 treatment was 83.4% higher than that in the deeper layer, and the surface accumulation rate of ammonium nitrogen reached 33.0% in winter. Under the coordinated regulation of water, potassium, and nitrogen, the above - ground dry matter mass under the W2K1N2 treatment in summer increased by 32.0% compared with the control, while the stem diameter in winter decreased by 8.6% due to low - temperature inhibition. The main effect of potassium fertilizer was significant in summer (p < 0.05), and nitrogen was the yield - limiting factor in winter, which confirmed the rule of "potassium promotes quality, nitrogen promotes yield". Season - specific water and fertilizer schemes were optimized based on the BBD - NSGA - II algorithm. In summer (W: 19.96 mm, K: 123.17 kg/hm², N: 198 kg/hm²), the simulated yield reached 151.55 t/hm², an increase of 93.1% compared with the control, and the soluble sugar increased by 18.9%. In winter (W: 28.03 mm, K: 182.51 kg/hm², N: 296.91 kg/hm²), the yield was 153.21 t/hm², an increase of 65.5% compared with the control, and the soluble sugar and vitamin C increased by 69.4% and 314.4% respectively. Conclusions: This optimization scheme provides a scientific basis for the efficient production of greenhouse white radishes, which can significantly improve the physiological indicators, yield, and quality of crops, and optimize the resource utilization efficiency. The cross - season water and fertilizer optimization scheme based on BBD - NSGA - II can achieve the coordinated improvement of yield and quality of greenhouse white radishes and the efficient use of resources, providing a theoretical basis and an intelligent decision - making paradigm for the precise regulation of greenhouse vegetables in cold regions.