Effect of land use change on soil physical and chemical properties of salinization farmland

In Hexi saline area of Gansu province,taking different salinization stage farmlands under the two land use types(Hordeum vulgare L.and Medicago sativa L.cultivations) as the study object,the effect of land use types on change process of soil physio-chemical characteristics of salinization farmland was studied.Results were as follows:(1) In the depth of 0-10cm,soil organic matter and alkali-hydrolyzable nitrogen content in alfalfa were in the following order: slightly salinized field(S1) non-saline field(S0) moderately salinized field(S2) severely salinized field(S3) very severely salinized field(S4);for barley,it was in the following order: S0 S1 S2 S3 S4,and there had different significant difference between different salinized farmlands under the two land use types.(2) In growing seasons,soil layers of soil water content greatly fluctuating in alfalfa was at 0-80cm,for barley,it was at 0-20cm soil layers.Although seasonal variations of soil water content in the two farmlands were all increased with salinization level reduced,the variations of soil water content in different salinized fields in alfalfa were higher than that of barley.(3) Different salinization level fields had different soil depths of salt accumulation and occuring the peak of average soil salinity under two land use types.In the composition of soil soluble salt ions and ratio,the same salinized level fields under the two land use types were similar;but in barley,the ratios of Cl-and Na++ K+in S0 and S1 were significantly higher than that of S0 and S1 in alfalfa,and the change ranges of different ions from S4 to S0 were lower than that of alfalfa.