Aiming at the problem of soil salinization in salinized irrigation area

the Urad irrigation area in the lower reaches of Hetao Irrigation District was taken as the research area

the spatial and temporal distribution and variation of water content and salinity (EC value) in surface soil (0-20 and 20-40 cm) and deep soil (40-100 cm) as well as the influence of groundwater depth on soil salinity were analyzed by the method of field measurement combined with laboratory experiment and statistical method of geostatistics. The results showed that:(1) Except for 0-20 cm in June (9.779%)

the variation coefficient of surface soil water content was 12.384%~19.667%

which was moderate variability

and the variation coefficient of deep soil water content was small (3.513%~9.757%)

which was weak variability. The variation coefficient of EC in surface soil was between 100.845% and 129.279%

which was a strong variability

while that in deep soil was between 83.685% and 98.853%

which was moderate variability. With the increasing of soil depth

the variability of water content and salinity decreased. (2) The soil water content and salinity in different periods had spatial structure characteristics within a certain range

which could be simulated by Gaussian model. The spatial correlation of soil water content in each layer was 0.038%~20.408%

and the spatial correlation of soil salinity in each layer was 0.043%~8.374%

both were less than 25%

indicating a strong spatial correlation

and this could be considered to be mainly caused by structural factors

and the spatial variability caused by autocorrelation was strong. (3) The soil salinity in the research area was mainly concentrated in the north salt wasteland. Due to strong evaporation

the capillary water in the aerated zone raised

and the soluble salts in the deep soil and groundwater were brought to the surface layer of the soil

resulting in the increasing of salinity

which was the typical salt-accumulation type. The immediate control and treatment were needed. At the same time

the soil salinity was greatly affected by the groundwater depth

the soil salinity increased with the decreasing of the groundwater depth. The relationship between the groundwater depth of the wasteland and the soil salinity satisfy was linear

and the relationship between he groundwater depth and soil salinity of the cultivated land was exponential. The soil salinity content in the 0-20 cm soil of the wasteland varied greatly with the depth of groundwater. The change trend of soil salinity with the depth of groundwater was smaller in 20-40 cm and 40-100 cm layers. When the groundwater depth of the cultivated land was 1~1.6 m

the soil salinity content changed greatly with the depth of groundwater. When the groundwater depth was more than 1.6 m

the soil salinity content changed little with the groundwater depth. This study provided an important theoretical basis and reference for the prevention and improvement of salinized soil in the lower reaches of Hetao Irrigation District.