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.