Yield and quality properties of alfalfa (Medicago sativa L.) and their influencing factors in China

Alfalfa (Medicago sativa L.) is the most valuable perennial forage crop, and assessing its yield and quality properties is essential to evaluate forage value of livestock production. However, regional patterns and controlling factors of the yield and quality of alfalfa have not been well documented. In this study, using a dataset of 7166 observations from 301 sites across the country collected from 334 publications, we explored the relationships between the yield and quality properties of alfalfa in China and the effects of environmental factors and management practices on them. The average dry matter yield of alfalfa was 11.18 ± 6.69 Mg ha-1, with average crude protein, ether extract, crude fiber, acid detergent fiber, neutral detergent fiber, crude ash, nitrogen-free extract, calcium, phosphorus and relative feed values of 19.05 ± 2.87%, 2.62 ± 0.97%, 27.16 ± 5.21%, 31.29 ± 5.58%, 40.48 ± 6.34%, 9.49 ± 1.59%, 38.67 ± 7.49%, 1.68 ± 0.55%, 0.25 ± 0.12%, and 151 ± 31.94, respectively. Alfalfa quality decreased with increasing yield. Geographically, alfalfa had higher yield and crude protein content in South China than in other regions. Quality was positively correlated with both precipitation and temperature, while yield showed a positive relationship with temperature but no significant relationship with precipitation. High soil nutrient availability (e. g., soil available nitrogen, SAN; soil available phosphorus, SAP; soil available potassium, SAK) improved the yield, while high SAN and SAP contents increased the crude protein content. The alfalfa yield increased and the quality decreased with advancing maturity and age, whereas increasing the number of harvests may benefit the quality. This study documents comprehensive information on the yield and quality of alfalfa and provides insights for policy makers for the effective management and sustainable development of alfalfa production.