5. Conclusions

It took nearly 10 years to conduct a field experiment of N addition onL. chinensis in MSSL. Nitrogen addition not only increased the contents of protein and fat, the ratio of K+/Na+ and Ca2+/Na+ of L. chinensisshoot, but also decreased the degree of soil salinization and increased soil fertility and the EMF. The suitable N addition rate of 90-120 kg N ha-1 effectively inhibited the yield, quality and soil degradation of L. chinensis in MSSL. Thus, scientific data once again proved that N addition was an effective and necessary measure to maintain the healthy growth of L. chinensis and inhibit land degradation in saline-sodic grassland of northern China.