Optimizing Nitrogen and Phosphorus Fertilizer Application for Wheat Yield on Alkali Soils: Mechanisms and Effects

Enhancing crop productivity on alkali soils is essential for food security; however, excessive fertilizer use can lead to soil salinization. Wheat, as a key staple crop, requires an appropriate nitrogen-to-phosphorus fertilization ratio to optimize its yield, yet the ideal ratio remains unclear. In this study, alongside the application of potassium and organic fertilizers, we investigated varying nitrogen application rates (100 kg/ha, 180 kg/ha) and phosphorus application rates (40 kg/ha, 80 kg/ha, 120 kg/ha). The results revealed that, under consistent nitrogen application conditions, when phosphorus application increased from 40 kg/ha to 80 kg/ha and 120 kg/ha, average yield increased by 13.6–25.1% and 0.1–12.6%, respectively. In contrast, under the same phosphorus application conditions, increasing nitrogen application from 100 kg/ha to 180 kg/ha resulted in a 2.6–17.6% increase in average yield. Among the factors considered, biomass emerged as the most significant determinant of yield (Standardized Path Coefficient (SPC) = 0.84), with key influences on biomass including soil alkali-hydrolyzable nitrogen, phosphorus uptake, and potassium uptake. The optimal fertilization strategy for wheat production on alkali soils was found to be 180 kg/ha of nitrogen and 80 kg/ha of phosphorus. These findings provide a theoretical foundation for optimizing fertilizer management in wheat cultivation on alkali soils.