Characteristics Of Soil Preferential Flow Movement In Sugarcane Fields Under The Influence Of Straw Returning

In order to explore the influence of straw returning on the preferential flow movement of the sugarcane field,this study took the sugarcane field in Guangxi as the research object.Through the field dyeing tracer experiment,the indoor infiltration experiment of the original soil column,combined with image analysis technology,ecological landscape pattern analysis,Water infiltration simulation and Logistic regression analysis methods,to explore the spatial characteristics of soil preferential flow and water infiltration movement,and comprehensively evaluate the factors affecting preferential flow.In order to improve the efficiency of water and fertilizer use in sugarcane planting in Guangxi,and to improve the related research on soil water movement of agricultural land under straw returning to the field,it provides corresponding scientific support and theoretical basis.The results of this study are as follows:(1)The staining morphology of the straw-covered sugarcane field is mainly clumpy,and the staining gradually decreases with the increase of soil depth.The average staining area ratio of the vertical section of the soil is the largest(37.95%).The staining morphology of the straw-covered sugarcane field increases as the depth increases.The shape differentiation,the dyeing water flow is concentratedly distributed,and the sugarcane field without straw cover is mainly in the finger-like dyeing form,and the average vertical section dyeing area ratio is the smallest(28.15%).The average shape index and the average near-circular index without straw mulch are 16.03 and 0.72,respectively,which are significantly larger than straw mulch and straw burning mulch,and the average proximity index is the smallest(0.83),which is significantly different from straw mulch and straw burning mulch(P<0.05).Under straw mulch,the difference of the average radius of gyration index of different soil depths was the smallest(0.48).The average edge density index of straw mulch and straw burning mulching sugarcane land at 10-50 cm soil depth was greater than that of no straw mulching.(2)The average outflow velocity of the undisturbed soil column of sugarcane without straw mulch was 0.83 m L·s-1,which was 2.24 and 4.61 times that of straw burning and straw mulching,respectively.Under straw mulch,the average outflow relative concentration is the smallest(0.79),and the time from solute infiltration to the average relative concentration is basically stable is the longest(440 min),and the opposite is the case under no straw mulch.When the simulations of different straw returning to the soil column reached a relatively stable state,the 50 cm soil depth saturation under straw mulch was the smallest(21.03%),and the soil without straw mulch was the largest(31.91%).The average substrate flow depth and average edge density index under straw mulch were the largest,12.90 cm and 12.60,respectively,and the preferential flow ratio was the largest(55.37%)without straw mulch.(3)The average soil bulk density of the unstained area of sugarcane fields with different straws was greater than that of the dyed area,and the average soil bulk density of the dyed(1.43 g·cm-3)and undyed(1.45 g·cm-3)areas under straw mulch were both the smallest.The soil average clay content in dyed(18.16%)and undyed(17.90%)areas under no straw mulch accounted for the smallest proportion.In the dyeing area,the average saturated hydraulic conductivity of the bottom layer soil covered with straw is the largest(1.15×10-2 cm·s-1),and the deep soil without straw coverage(8.25×10-4 cm·s-1)is the largest,and straw mulching The average organic matter content is the highest(26.25 g·kg-1),while the average total nitrogen content of the soil covered with straw burning is the highest(0.29 mg·g-1),and the average total phosphorus content of the soil is the highest with straw mulching(0.34 mg·g-1).The chemical properties of the soil under the same straw returning to the field have a more significant impact on the priority flow of sugarcane fields.Compared with no straw mulch,straw mulch and straw burning mulch have significant effects on soil bulk density and soil clay content,respectively.In the comparative analysis of straw mulch and straw burning mulch,the significant influence factor of preferential flow is soil bulk density.