Effects of an arbuscular mycorrhizal fungus and rhizobium on the growth and nutritional value of Medicago sativa

The present research aimed to study the effects of the rhizobium Sinorhizobium medicae (S+) and arbuscular mycorrhizal fungus (AMF) Funneliformis mosseae on the growth and nutritional value of alfalfa (Medicago sativa ‘Longdong’) in a greenhouse. The results showed that the influence of the rhizobium and AMF on alfalfa growth and nutritional value varied with different cuttings. Compared to the NMS (dual inoculation of rhizobium and AMF) treatment, the dual inoculation of AMF and rhizobium significantly increased the shoot, root, and total biomass of alfalfa by 114.17%, 42.10%, and 24.32% (P < 0.05) for the first cutting, respectively. At the same stage, AMF alone increased the phosphorus content of alfalfa by 45.53% (P < 0.05). However, the individual inoculation of rhizobium decreased the stem to leaf ratio by 33.76% (P < 0.05) for the third cutting. AMF + rhizobium increased the neutral detergent fiber (NDF) content of alfalfa for the third cutting (P < 0.05). Except for that mentioned above, the AMF and rhizobium did not affect the growth or nutritional value of alfalfa. Cuttings improved the plant growth. Compared with the first cutting, the plant height, shoot biomass, NDF content, and acid detergent fiber (ADF) content of alfalfa improved by 79.42%, 72.50%, 15.19%, and 26.50% (P < 0.05), respectively, while the nitrogen content and relative feeding value (RFV) decreased by 13.51% and 18.03% (P < 0.05) for the second cutting, respectively. For the third cutting, the plant height, branch numbers, stem to leaf ratio, NDF content, and ADF content of alfalfa were 105.97%, 26.20%, 119.23%, 47.63%, and 58.07% (P < 0.05) higher than those of the first cutting, respectively, while the N content and RFV decreased by 12.67% and 40.92% (P < 0.05), respectively.