Ecological stoichiometry characteristics of soil and plant of alfalfa with different growing years on the Loess Plateau

To investigate the changes inw nutrients in soil-vegetation ecosystems, Medicago sativa at different ages (1, 10, 20, 30 years) was selected to analyze variations in the nutrient content and characteristics of eco-chemical stoichiometry. The results showed that: 1) the content of soil organic carbon (SOC) and total nitrogen (TN) first increased and then decreased as age increased, the vertical distribution of SOC and TN at a soil depth of 0–200 cm was consistent at all alfalfa grasslands, and the content of SOC and TN at a soil depth of 0–30 cm was higher than that at 30–200 cm. However, the content of soil total phosphorus (TP) was stable throughout the soil layer. The ratios of soil C∶N, C∶P, and N∶P showed similar dynamic patterns to soil carbon and nitrogen. 2) The content of C, N, and P in the leaf was similar to that in soil, with maximum values observed at 10 years. The ratios of leaf C∶N, C∶P, and N∶P first decreased and then increased. 3) There was no significant correlation between the stoichiometry characteristics of the soil and plant (P > 0.05). These results indicate that after 10 years, some management measures should be taken to improve the quality of soil and growth of alfalfa.