Revisiting the effect of fertilizer application on biomass accumulation in alfalfa: roles of fertilizer type, application rate, and environmental condition

An insufficient supply of high-quality forage is a critical factor constraining the development of the livestock industry. Cultivated grasslands, such as alfalfa (<italic>Medicago sativa</italic> L.), play a vital role in addressing this issue. Fertilizer application is an effective strategy for sustaining alfalfa production; however, optimizing management practices is essential for alfalfa to adapt to variable environmental conditions. In this study, 169 published papers encompassing 1,595 pairs of experimental data spanning from 1957 to 2022 were compiled. A meta-analysis was conducted to evaluate the effect of fertilizer application on biomass accumulation in alfalfa at the first cut, considering fertilizer type, application rate, and environmental factors. Compared with no fertilizer application, fertilizer application significantly increased biomass accumulation in the first cut alfalfa by 17.7% overall. The applications of nitrogen, phosphorus, potassium fertilizers, and manure significantly increased biomass accumulation by 12.4%, 24.0%, 13.1%, and 38.0%, respectively, compared to no fertilizer application. Few differences were detected in improving alfalfa production among the application rates of the three chemical fertilizers. The recommended ranges for application rates of the three chemical fertilizers were 100–150 kg·ha⁻¹. Mean annual temperature, and mean annual precipitation had limited effects on increasing biomass accumulation with fertilizer application, which varied among the four fertilizers. Soil conditions exhibited various regulatory effects on biomass accumulation in response to application of the four fertilizers. These findings provide valuable insights to help optimize fertilizer management strategies in alfalfa production by considering environmental conditions. Future research should focus on the prolonged effect of fertilizer application, fertilizer type and/or site-specific variation, and provide guidance for the sustainable utilisation of alfalfa grassland under diverse environments.