| In this paper, based on the soil data of Shahaoqu irrigation system and Jiefangzha irrigation area at two scales in Hetao irrigation district, used the traditional hydrometer method and laser diffraction method to analyze the consistency of the soil particles; And conducted a study of spatial variability of the soil textures and the organic matter contents at two scales by combinating the classical statistics and geostatistics; Drew and analyzed their spatial distribution patterns with analyzing its scale effects. GSWAP model was used to simulate soil water-salt regime at two scales of Shahaoqu irrigation system and Jiefangzha irrigation area. Results could provide theorical basis and reference for regional management and optimizing water saving strategy. The main research results for this study were as follows:(1) There were many differences of the soil particles measured by laser method and hydrometer method. The clay contents measured by the laser method were lower than those tested by the hydrometer method, while the sand contents measured by the former were higher than those by the later. The silt contents varied with no consistent difference. The transfer equations between the data measured by two methods were: the clay yhydrometer=3.753xlaser+2.8587; the silt yhydrometer=0.9555xlaser+3.388; the sand yhydrometer=1.0733xlaser-18.32. The converted data could effectively improve the consistency of the soil particles.(2) The results of the spatial variability of the soil particles and the soil organic matter at different scales shows that:(a) the coefficients of variation increased with the soil depth increasing under the same scale, and increased with spatial scale increasing at different scales. The values of the coefficient of variation were between10%and100%, all spatial variabilities were moderate variability,(b) Range decreased with soil depth increasing under the same scale, while increased with sampling scale increasing at different scales. Different soil properties showed the different range. The autocorrelation range of the surface clay was the largest. There were similar variation pattern between silt and sand,(c) The value of C/(C+CO) increased as the increase of soil depth under the same scale. The soil structural property and the spatial correlation enhanced. Different soil properties showed the different variation patterns. That of the silt and the sand both had a constant spatial correlation.That of the clay and the organic matter almost not changed. Except the clay and organic matter of the surface soil were moderate spatial correlation, others showed a strong spatial correlation,(d) The0-20cm sampling soil of the clay and the organic matter at large scale could representment that at small scale to show the spatial structure at Shahaoqu and Jiefangzha. As the spatial scale increased, the leading factor of the spatial structure changed.(3) The GSWAP model was used to simulate soil the water and salt regime at different scales and the results showed that:(a) During the whole crop growing period, the groundwater recharged the soil water in spring wheat and corn fields to meet the groupth, while the deep percolation was taken for sunflower. some irrigation water was wasted.(b) Different crop had different response mechanism to salinity and groundwater depth. The water flux and salt flux on the area had a large spatial variability. The processes of spring wheat and corn fields in Shahaoqu were the salt accumulation process, while the desalination for sunflower fileds. The regional water productivities of spring wheat, corn and sunflower of WPET in Shahaoqu were1.396kg/m3,1.762kg/m3and1.164kg/m3. The regional water productivities of spring wheat, corn and sunflower of WPET in Jiefangzha were1.199kg/m3,1.835kg/m3and1.092kg/m3. |
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