| The soil erosion is serious, then the water storage and soil retention ability are poor in purple soil area. Soil infiltration has been an important part on study of soil erosion, and it has been also the key link of rainfall flow and water cycle in soil. At present, the study on determination of soil infiltration capability were more by different methods in purple soil area. However, the application of point-source infiltration method in the area has not yet begun. Thus the point-source infiltration method, double-ring method and cutting ring method were applied to determinate the soil infiltration capability in this area. For evaluating their applicability in purple soil area, the differences of the experimental results among different methods were compared. In order to solve the law of soil water infiltration, combining the influence factors with performance correlation of different land-uses. It has important significance for the study of soil infiltration in purple soil area. The results obtained in this paper are as follows:(1) The rule of evaluating soil infiltration of point-source infiltration method was the best among three infiltration methods, double-ring method and cutting ring method were followed. The infiltration rate of the initial value and the stable value determined by three methods has a larger gap. The gap of point-source infiltration method in 6～9 times, double ring method in 1～10 times, cutting ring method in 0.3～2 times. The consuming time of point-source method was the least, cutting ring method and double-ring method were followed. In the repeated test, the difference among initial values of point-source infiltration method was minimum in the three methods. The maximum difference only from 28% to 58%, and the stable values are uniformity. Cutting ring method was followed, its maximum difference of initial values was in 0.3～1 times, and the difference of stable values was in 0.7～1.4 times. The maximum difference of initial values was in 8%～38% and stable values was in 1～6 times of double-ring method.(2) There are some differences among infiltration capacity parameters of different land-uses. The initial infiltration rate, the former 20min average infiltration rate and average infiltration rate of point-source infiltration method were manifested as woodland> slope cropland> grassland. And stable infiltration rate was slope cropland> woodland> grassland. The initial infiltration rate, the former 20min average infiltration rate, stable infiltration rate, average infiltration rate and the former 90min cumulative infiltration of cutting ring method were manifested as woodland> grassland> cropland slope. And the double-ring method were shown as woodland> slope cropland> grassland. Moreover, the reaching stable state:point-source infiltration method double-ring method were slope cropland> woodland> grassland, cutting ring method was grassland> woodland> slope cropland.(3) There are also some differences among infiltration capacity parameters of different land-uses in repeated test. The difference of initial infiltration rate measured by point-source infiltration method was shown grassland> woodland> slope cropland, stable infiltration rate was slope cropland> grassland> woodland, average infiltration rate was woodland> grassland> slope cropland. The difference of initial infiltration rate, stable infiltration rate and the former 90min cumulative infiltration measured by cutting ring method was shown woodland> slope cropland> grassland, average infiltration rate was woodland> grassland> slope cropland. And the difference of initial infiltration rate measured by double-ring method was shown grassland> woodland> slope cropland, stable infiltration rate was woodland> slope cropland> grassland, average infiltration rate and the former 90min cumulative infiltration was woodland> grassland> slope cropland.(4) The infiltration capacity measured by different methods in purple soil area was shown as:initial infiltration rate was point-source infiltration method> double-ring method, the former 20 min average infiltration rate was opposite. Stable infiltration rate was double-ring method> cutting ring method> point-source infiltration method, average infiltration rate was double-ring method> point-source infiltration method> cutting ring method, the reaching stable state was double-ring method> cutting ring method> point-source infiltration method. The former 90min cumulative infiltration of double-ring method was larger 1-6 times than cutting ring method. The infiltration capacity parameters(initial infiltration rate, the former 20min average infiltration rate, stable infiltration rate, average infiltration rate, the former 90min cumulative infiltration and the reaching stable state) among three land-uses were shown:woodland> slope cropland> grassland.(5) There are some differences about fitting effect of soil infiltration measured by three methods though 4 infiltration models. And the fitting effect of point-source infiltration method was shown:Horton model> general empirical model> Kostiakov model> Philip model. In addition to the slope cropland, the fitting effect of double-ring method was shown:general empirical model> Horton model> Kostiakov model> Philip model, and the fitting effect of cutting ring method was shown:Horton model> general empirical model> Kostiakov model> Philip model.(6) A greater infiltration rate was found in the initial, and then the infiltration rate decreased slowly, and finally reached a constant point of double-ring method and cutting ring method. In addition, the change curve of cumulative infiltration in three land-uses soil infiltration processes shown a dispersed state, and woodland’s was the most obvious, following with grassland and slope cropland. Equation of a degree and equation of two degree were used to fit the cumulative infiltration measured by two methods, the fitting effects were good, and the former was better. The effect of using equation of two degree to fit cumulative infiltration of three land-uses was shown grassland> woodland> slope cropland, and the effect of using equation of a degree was shown grassland> slope cropland> woodland. Then the double-ring method was better than cutting ring method for the fitting effect.(7) Soil physicochemical properties have different impacts on its infiltration capacity, but the generally rules are followed:non-capillary porosity and structure damage rate show positive influence with initial infiltration rate and cumulative infiltration. Otherwise, soil bulk density, soil water content, capillary porosity, content of aggregates> 0.25mm, organic matter content and dry sieving MWD value show the opposite tendency. Non-capillary porosity, content of aggregates> 0.25mm, organic matter content and structure damage rate have positive impacts on stable infiltration rate, but soil bulk density, soil water content, capillary porosity and dry sieving MWD value show negative feature. Also, a positive relationship is found between average infiltration rate and non-capillary porosity, organic matter content and structure damage rate, a negative relationship is observed with soil bulk density, soil water content, capillary porosity, content of aggregates> 0.25mm and dry sieving MWD value.(8) In order to analyze the applicability of different infiltration methods, their advantages and disadvantages were contrasted though test results in purple soil area. Point-source infiltration method is more accurate, time-efficiency, water saved and more convenient to calculate compared with double-ring method. When compared to cutting ring method, point-source infiltration method has a wider experimental scope, better representation and more objective to simulate infiltration process. Although, point-source infiltration method is an advanced method, but some defects are found, such as high expenditure and temporal restricted. Overall, point-source infiltration method is a capable to be applied in purple soil region but still need improved to overcome its defect. |
PDF Full Text Request