| Soil salinization is the main reason that restricting the sustainable agriculture development of Jiefangzha irrigation field in Hetao Irrigation District,Inner Mongolia.Soil salinization not only affects the crop diversity in this study area,but also reduces the fertility of cultivated land,thus restricting the development of local economy.In recent years,with the cut down of irrigation water diversion,salinization degree relieved with the groundwater level decline,however,the new water and salt dynamic balance has not been formed as the drainage volume(salt excretion)was also reduced,soil salinization is still the main threat to irrigated agricultural production development.Therefore,it is important to analyze the spatial and temporal variability of groundwater depth and salinity as well as discuss their relationship with soil salt content.It is with great significance for water-saving irrigation and preventing soil salinization to determine the critical depth and mineralization that preventing soil desalinization.In order to discuss the effects of groundwater depth and salinity on soil salinization,taking Jiefangzha irrigation field of Hetao irrigation district Inner Mongolia as a study area,the spatial and temporal distribution of groundwater level and mineralization and the spatial distribution of surface soil salinity were analyzed by using the geostatistical method(indicator Kriging)based on the existing data collected and investigated in this paper.The relationship between soil salinization and groundwater depth was discussed in this paper,preliminarily determined the critical value of groundwater depth and mineralization(a certain value of the variable,when the groundwater depth is less than or a value greater than it,the probability of mineralization is large and the surface soil salinity of the risk is greater)for slight soil and medium salinization,thereby providing a basis for prevention and control of local soil salinization.The main research contents and conclusions are as follows:(1)The spatial distribution map of the probability for threshold under different groundwater depth and water mineralization levels were drawn by using the indicator Kriging method,and were compared and verified with the soil salinization risk distribution(i.e.the spatial distribution of probability for soil salinity is greater than 2g/kg or 3g/kg)and the saline soil type distribution map obtained by remote sensing.The results show that:the critical value of groundwater depth is 2m and 2.5 m when the surface soil(0-10cm)occur medium or slight salinization in the end of April,respectively.The surface soil(0-10cm)salinization risk distribution is less fit with the probability distribution of the groundwater depth that less than 2m or 2.5m during March to April than that only consider the groundwater depth in the end of March,which indicating that the soil desalinization in April in mainly rely on the former ground water depth.The groundwater mineralization critical were value 2.5g/L and 3g/L when the surface soil(0-10cm)occur slight and medium salinization in the end of April,respectively.in the end of April,The probability distribution of mineralization that greater than 2.5g/L or 3g/L during March and May is less fit with surface soil(0-10cm)salinization risk distribution than that only consider the mineralization in March,which indicates that the probability distribution of mineralization in the early March is more similar the soil salinization distribution in the end of April.(2)The spatial distribution map of the collaborative probability for groundwater depth under different critical value and water mineralization levels were drawn by using the indicator Kriging method,and were compared and verified with the soil salinization risk distribution(i.e.the spatial distribution of probability for soil salinity is greater than 2g/kg or 3g/kg)and the saline soil type distribution map obtained by remote sensing.The results show that the surface soil is susceptible to slight salinization when the groundwater depth is less than 2.5 m and and mineralization is greater than 2?2.5g/L;the surface soil is susceptible to medium salinization when the groundwater depth is less than 2 m and mineralization is greater than 2.5-3g/L.While,the analysis of groundwater depth during March and mineralization situation of March and May,the spatial distribution map of the collaborative probability that considering the groundwater depth during March to April and mineralization in the early March is similar to that considering the groundwater depth in later March and mineralization in the early March.The probability distribution of late March during the 2009 to 2012(for three years)is similar to that of the later March in 2012 when the groundwater depth is less than 2m,which indicates that the high probability of groundwater depth less than 2m is relatively stable.The probability distribution of early March during the 2009 to 2012(for three years)is similar to that of the early March in 2012 when the mineralization of water is greater than 2.5g/L,which indicates that the high probability of the mineralization of water is greater than 2.5g/L is relatively stable.The probability distribution of groundwater depth in late March and mineralization in early March during the 2009 to 2012(for three years)is similar to that in 2012 when the groundwater depth is less than 2 m and mineralization of water is greater than 2.5g/L,which indicates that the high probability of the groundwater depth is less than 2 m and mineralization of water is greater than 2.5g/L is relatively stable.(3)According to the spatial and temporal distribution of groundwater depth and mineralization in this study area,it is suggested to improve the drainage and irrigation canal lining,combine well and canal,improve field irrigation technology and the management level of irrigation and other water conservancy engineering measures,as well as improve agriculture,biological and chemical prevention measures in the area of serious soil desalinization. |
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