Phosphorus Improves Stoichiometric Characteristics of Saline-Sodic Soil and Alfalfa

Background: To optimize saline-sodic soil amelioration strategies, enhance soil fertility and forage productivity, and elucidate aluminum sulfate's regulatory mechanisms on C-N-P stoichiometric characteristics in both saline-sodic soils and alfalfa, we conducted this study at Yinlang Ranch of Daqing City, Heilongjiang Province in China. Results: This study investigated the effects of aluminum sulfate application at different doses (0, 24, 48, and 72 kg·hm ^-2 ) on the distribution of carbon (C), nitrogen (N), and phosphorus (P), as well as stoichiometric ratios and environmental factors of alfalfa and soil layers. The results indicated significant differences in the C-N-P stoichiometric characteristics of soil and alfalfa under different aluminum sulfate applications. An application rate of 48 kg·hm ^-2 significantly increased the C, N, and P contents in both soil and alfalfa while maintaining a relatively stable soil N/P ratio. Soil C and P exhibited significant positive correlations with alfalfa P. During the growth process, alfalfa growth was primarily limited by P. The plants enhanced their growth and development by adjusting the balance between elemental requirements and nutrient absorption, as well as modifying nutrient utilization strategies to adapt to the saline-sodic soil environment. Furthermore, alfalfa P showed significant negative correlations with soil pH and electrical conductivity (EC). Conclusions: The study concludes that aluminum sulfate significantly influences the C-N-P stoichiometric characteristics of the soil-alfalfa system. The optimal application rate of 48 kg·hm ^⁻2 enhanced nutrient content in soil and alfalfa, stabilized the soil N/P ratio, and promoted P uptake of the alfalfa by improving soil environmental conditions. These findings establish a theoretical foundation for precision nutrient management.