3.3 The relationship between L.chinensis quality and soil chemical characteristics
In order to clarify the effects of soil salinity and nutrients on the quality of L. chinensis , RDA was conducted between L. chinensis quality and soil chemical characteristics. The results of RDA revealed that the variance ratio of RDA1 (35.20%) reached a significant level in the biplot (P <0.01), there were some negative correlations between soil salinity (pH, EC and ESP) and most quality indexes of L. chinensis (except for Na+ and coarse fiber content), and there were some positive correlations between SOM, Sucrase, Urease and most quality indexes (Fig.6). RDA also indicated that L. chinensis had higher Na+ and coarse fiber in no N addition or low N addition treatments (N 0-90), which was mainly related to higher salinity in soil, on the contrary,L. chinensis had higher contents of K+, Ca2+, Mg2+, protein and fat in high N addition treatments (N 120-210), which was mainly related to higher SOM contents, urease and sucrose activities. Thus, N addition increased the quality of L. chinensis mainly through improved soil nutrient contents, especially carbon and N contents in saline-sodic soils.