Spatialtemporal Variation of Soil Salinity after Water Saving Transformation in Salinized Irrigation District
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    Abstract:

    After the transformation of water saving, the soil salinity of Shenwu Irrigation Area was redistributed due to the change of groundwater level. Based on regional soil information fixed point monitoring, the classical statistics, spatial interpolation, buffer analysis and spatial autocorrelation analysis methods were used to study the spatial variability, temporal and spatial distribution of soil salinity and the difference of soil salinity change in regions for a fixed number of different transformation years. The results showed that after water saving transformation, the average salt content of the whole soil was decreased by 730% before autumn irrigation, the amount of water poured in autumn irrigation was decreased, and the leaching effect of soil salinity was decreased by 926% after autumn irrigation. In the space domain, the high value of soil salinity (great than 6g/kg) was located in the northeast and southern regions with shallow groundwater depth, and the low value of soil salinity (less than 2g/kg) was located in the southwest and eastern sand areas. After water saving transformation, the average increase amplitude of soil salt global Morans I index before autumn irrigation was 5%, the spatial correlation was enhanced. The water volume of autumn irrigation water quantity was decreased, and the global Morans I index was changed, but it was not significant, and the influence of autumn irrigation on soil salinity spatial autocorrelation was weakened. According to the analysis of LISA cluster map, it was revealed that the high-high spatial pattern in the south before autumn irrigation was changed to nonsignificant and high-low cluster area, and the cluster characteristics in the south after autumn irrigation were still very significant, there was salinization risk zone, and it was still the key area of salinization prevention and control after transformation. For moderately saltresistant crop, the proportion of crop growth safety zone and deep nonsaline soil area in Shenwu Irrigation Area was 4966% and 7157%, respectively, after transformation, the area of crop growth safety zone and deep nonsaline soil was increased by 482 percentage points and 185 percentage points, respectively, before autumn irrigation, and decreased by 502 percentage points after autumn irrigation, but the change in deep layer was not significant. The explanatory capability of the average soil salt content in different distance buffer was strong. The affecting radius of the longterm and shortterm transformation regions was 15km and 07km, respectively. The falling rate of average soil salinity content in the buffer of the longterm transformation region was higher than that in the shortterm transformation region, and the degree of homogenization was higher. In summary, since project of watersaving transformation, the degree of soil salinization was reduced, the area of crop growth safety zone was increased, the surface accumulation was weakened, the amount of autumn watering was reduced, the influence of autumn irrigation on soil salt spatial autocorrelation was weakened, and the soil environment was improved. It was suggested that subsurface pipe drainage and chemical improvement agent should be used in the risk area of local salinization.

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History
  • Received:May 11,2019
  • Revised:
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  • Online: February 10,2020
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