Abstract: The measures of returning straw to the field can change soil environment in the field and affect crop growth. In order to explore the impacts of different straw returning measures on the preferential flow in the field, we investigated the movement characteristics of preferential flow in sugarcane fields under different straw returning measures [straw mulching (CM), straw burning mulching (BM), and non-straw mulching (CK)] in Guangxi by combining image analysis techniques with ecological landscape pattern analysis methods. The results showed that under the same external water supply environment, soil staining morphology of non-straw mulching sugarcane fields differentiated into finger-like and clump-like. Both straw mulching and straw burning mulching were mainly differentiated into clump-like. The mean total staining area ratio was significantly higher than that of non-straw mulching (26.0%). The ratio of surface staining area decreased rapidly under non-straw mulching. The water movement range decreased rapidly under straw mulching and straw burning mulching in the depth of 15-30 cm. The change rate of straw mulching staining area ratio was the lowest in the deep soil. The shape index of non-straw mulching was 15.54. The water flow movement was more concentrated. The average sub-circular index of straw mulching and straw burning mulching was 0.67 in the sugarcane field, with a higher degree of preferential flow bending, an average proximity index of 0.87, and better water flow connectivity. The average substrate flow depth (3.52 cm) and edge density index (11.51) were the smallest under non-straw mulching, but the priority flow ratio was the largest (73.2%), and the spatial development degree of preferential flow was the highest. The straw returning measures reduced the preferential flow in the sugarcane fields, with positive effects on water conservation.

Key words: sugarcane field, straw returning to field, landscape pattern, preferential flow