Abstract:Soil salinization is the main obstacle to agricultural development in arid areas, and groundwater environment is the direct factor affecting soil salinization in shallow groundwater areas. In order to control reasonable groundwater depth and salinity to prevent and control regional salinization, the Yongji Irrigation Area in Hetao Irrigation District was used as the research area, the probability distribution diagram of soil surface salinity and groundwater depth and groundwater salinity under different threshold conditions before spring irrigation period and during growth period was analyzed and compared by using indicator Kriging method. The critical groundwater depth and salinity when soil salinization occurred in different periods were analyzed from the perspective of probability spatial distribution. The results showed as following: the groundwater depth was medium variability, while the surface salinity and groundwater salinity were strong variability. Before spring irrigation, compared with the growth period, the high risk areas of soil surface salinization were increased, the high probability areas of shallow groundwater were decreased, and the high risk areas of groundwater mineralization were decreased. Before spring irrigation, the critical buried depth of groundwater in the soil surface layer of Yongji Irrigation Area when mild and moderate salinization occurred was 2.6 m and 2.2 m, and the critical salinity of groundwater when mild and moderate salinization occurred was 2.0 g/L and 2.5 g/L, respectively. During the growth period, the critical depth of groundwater under mild and moderate salinization was 2.2 m and 1.8 m, and the critical salinity of groundwater under mild and moderate salinization was 2.5 g/L and 3.0 g/L, respectively. Soil salinization was more likely to occur before spring irrigation. Soil salinity before spring irrigation was less affected by external factors (meteorological factors and human factors) than that during the growth period. Moreover, soil surface salinity, groundwater depth and salinity variability before spring irrigation were relatively small, groundwater environment had strong impact on soil salinization. The northern, southeastern and central parts of the study area were areas with high probability that the groundwater was less than the critical burial depth and greater than the critical salinity, which were areas with high risk of soil salt return. It was suggested to further improve the drainage system and reduce the groundwater depth and salinity in local salinization risk areas.
