Meta-analysis on response of soil moisture, nutrients, and alfalfa yield to fertilization based on location test data

Alfalfa (Medicago sativa) is an important forage crop for livestock feed that contributes nitrogen to succeeding crops in crop-rotation systems. A meta-analysis was conducted to determine how fertilization strategies affected forage yield and soil fertility of alfalfa fields in China. Non-fertilizer was used as control treatments in this research. Based on the published data of relevant location test and the meta-analysis, the quantitative effects on fertilizer application on alfalfa with respect to soil water content, nutrients, yield, and WUE were studied. The results showed that fertilization could improve soil nutrients and alfalfa yield, whereas an increase in alfalfa biomass resulted in a decrease in soil water content. Fertilization increased soil organic matter and nitrogen by 3.1% ~ 33.3% and 4.5% ~ 30.9%, respectively. Similar trends were observed with respect to soil available phosphorus and available potassium, which increased by 3.6% ~ 144.4% and 4.4% ~ 24.8%, respectively. However, owing to the increase in alfalfa biomass, the soil water content decreased by 4.4% ~ 11.8%. As a result, the alfalfa yield and WUE improved by 15.4% ~ 198.2% and 5.9% ~ 169.6%, respectively. Correlation analysis showed that the alfalfa yield was positively correlated with soil water content at 0 – 200 cm, organic matter and available phosphorus; the WUE of alfalfa was positively correlated with soil available phosphorus. In conclusion, fertilization could improve soil nutrients as well as alfalfa yields. The combined application of organic and inorganic fertilizers is an optimum strategy for increasing alfalfa yields, while the combined application of N, P, and K fertilizers is better for WUE. These findings can provide a strategy for farmers to enhance the sustainability of the alfalfa system through fertilization management.