秸秆覆盖下桂北岩溶区水稻田土壤优先流特征

优先流作为一种土壤水分的快速入渗形式,广泛发生于水稻田内。通过进行野外土壤染色示踪试验,结合形态学图像解析技术,开展秸秆覆盖与非覆盖条件下的广西岩溶区水稻田土壤优先流特征研究。结果表明:在相同的外部供水条件下,秸秆覆盖水稻田土壤染色形态以整体均匀分布形式为主,而非秸秆覆盖水稻田呈明显枝状染色形态分化现象并贯穿整个土壤空间,其平均染色斑块形状系数为13.96,染色形态表现为显著不规则分化状况,且土壤空间中染色水流平均分布密度达0.117,相比秸秆覆盖水稻田更大,呈现染色水流集中分布状态。秸秆覆盖水稻田土壤入渗量相比非秸秆覆盖水稻田较高,平均总染色面积比达46.69%,二者之间差异显著(P0.05),但田间优先流发生时间相对较晚,对应的平均基质流深度为16.92 cm,优先流比显著小于非秸秆覆盖水稻田(49.55%)(P0.05),仅为27.47%。秸秆覆盖措施可影响田间土壤水分运动过程,在一定程度上提高田间水分的入渗量,降低土壤优先流发生程度,促进稻田土壤水分的保持,减少田间水肥流失。

The Characteristics of Preferential Flow on Straw Mulching of Paddy Field in the Karst Region of North Guangxi

Preferential flow is a rapid infiltration form of soil moisture which occurs widely in paddy fields. This paper concentrated on typical farmland of paddy fields with straw mulching and non-cover conditions in the Karst region of Guangxi, using the methods of brilliant blue dye and the morphological image analysis technology to present the soil preferential flow features of two tillage types. The results showed that under the same water supply condition, the soil dyeing morphology of straw mulching paddy fields was mainly uniformly distributed, while the non-mulching conditions paddy fields showed obvious branch-like dyeing morphological and throughout the soil space. The average dyed patch shape coefficient of non-mulching conditions paddy field was 13.96, and the dyeing morphology showed a significant irregular differentiation. The average distribution density of dyeing water in soil space was 0.117, which was larger than that straw mulching paddy field, showing a concentrated distribution condition of dyeing water. The soil infiltration capacity of straw mulching field was higher than that of non-cover conditions paddy field, with its the average total dyeing area ratio was 46.69%. There was significant difference between them (P<0.05). But the time rate of preferential flow of straw mulching paddy field was later than the non-mulching conditions paddy field, which the average matrix flow depth was 16.92 cm. The preferential flow fraction of straw mulching paddy field was 27.47% less than the straw mulching rice paddy (49.55%). There was significant difference between them (P<0.05). Straw mulching method can affect the process of soil water movement in the field. At the same time, its increase the amount of water infiltration in the field to a certain extent and reduce the occurrence of preferential flow. Compared with the non-cover conditions of paddy field, the straw mulching method also promote the maintenance of soil water in the paddy field, and reduce the loss of water and fertilizer in the field.