Analysis and evaluation of soil salinization in oasis of arid region

Alashan Prefecture pastoral area of Inner Mongolia was atypical arid area,where mineral,land and agricultural resources were very rich.However,a large area of soil was salinized due to irrational development,which resulted in grassland degradation and desertification increasing,and seriously obstructed and constrained sustainable development of local agricultural economy.Soil salinization has become one of the important factors to limit economic sustainable growth.Therefore,it is important to analyze and evaluate soil salinization of this typical arid oasis.In order to find out the distributing characters of soil salinization,the 61 soil profiles were emplaced proportionally in studying area.Soil salinity,pH value and ion contents of 0-10 cm,10-20 cm,20-40 cm,40～70 cm,70～100 cm and 100-150 cm soil layer were analyzed.At the same time total dissolved solid(TDS) of 16 water samples in unconfined aquifer were collected and tested.According to analysis results,the following subjects were studied:soil salinity distribution patterns of plough layer,variety patterns of soil salinity in different seasons, calcium carbonate profile in different layers and mineralization isopleths of unconfined aquifer.Then the influencing factors of soil salinization were analyzed.Prevention measures were provided.The results showed as flows:(1) The area of soil salt content which was higher than 1%accounted for 32%of the whole region,and the salt contents of soil in southwest part were higher than that in northeast part,which was consistent with the distribution of the total dissolved solid(TDS) of water in unconfined aquifer.These indicated the phenomenon of soil salinization was widespread and the main reason of soil salinization is due toirrigation water quality.(2) The primary soluble ions were Na~+ and SO_4~(2-)、Cl~-,it is reputed that the first cause of soil alkalization is created by Na_2SO_4 and NaCl.Testing results of pH value show that the pH value of soil in the majority was higher than 8.5,which illuminated it had the double characteristics of salinization and basification.(3) The soil salinity represents the significantly seasonal varying.On the soil profile strong lime reaction was obvious from top to down,most of calcium carbonate was accumulated in the middle or lower layer,and the accumulated depth of calcium carbonate became deeper and deeper gradually from east to west.(4) In order to amend and develop the saline soil,comprehensive planning and reasonable layout should be needed.Agriculture,forest,and pastures should be developed based on the local conditions. In order to prevent the damage of eco-environment and salinization,in the saline plowland,the soil fertility should be improved.The study results provided a theoretical basis and practical reference for the study region as well as the vast arid area oasis to manage scientifically,use rationally and improve precisely salinized soil.