Effects of Combined Application of Organic and Chemical Fertilizers on Nutrient Accumulation and Utilization Efficiency of Alfalfa

Global demand for alfalfa, a vital forage resource for ruminants, is growing. Currently, ruminant production is expanding rapidly in parts of Asia and Africa, further driving demand for high-quality alfalfa forage. Nevertheless, long-term indiscriminate fertilization and imbalanced nutrient input ratios in alfalfa production not only lower fertilizer use efficiency and crop productivity but also induce a range of soil degradation and environmental issues, thereby constraining the sustainable development of the forage-livestock industry. In this study, the alfalfa cultivar ‘Xinmu No. 4’ (Medicago sativa cv. ‘Xinmu No. 4’) was used as the experimental material. A two-year field block experiment was performed to investigate the effects of different organic–inorganic fertilizer ratios on the nutrient use efficiency of alfalfa, with six fertilization treatments: CM0 (100% cow manure), CM1 (75% cow manure + 25% chemical fertilizer), CM2 (50% cow manure + 50% chemical fertilizer), CM3 (25% cow manure + 75% chemical fertilizer), CM4 (100% chemical fertilizer), and CK (no fertilization application). The results demonstrated that the CM3 treatment (25% cow manure combined with 75% chemical fertilizer) significantly enhanced nitrogen, phosphorus, and potassium accumulation in alfalfa relative to the CK, sole cow manure (CM0), and sole chemical fertilizer (CM4) treatments (p < 0.05). Additionally, plant nutrient accumulation in 2025 was markedly higher than that in 2024 across treatments (p < 0.05). Combined organic and inorganic fertilization substantially improved the agronomic use efficiency of nitrogen, phosphorus, and potassium in alfalfa, with the CM3 ratio exhibiting the most pronounced beneficial effect. For alfalfa cultivation in Xinjiang, the combined application of 25% cow manure and 75% chemical fertilizer is recommended to optimize nutrient accumulation and utilization efficiency, ultimately boosting alfalfa yield and quality.