Distribution pattern of rainwater in soil under vertical deep rotary tillage in dryland farmland

Abstract

In semi-arid areas, drought is the main limiting factor for rainfed agriculture. Vertical rotary subsoiling (VRT) has been shown to effectively increase soil water storage and so allow crops to resist seasonal drought. However, there is a lack of reports on the infiltration path and distribution pattern of rainwater in soil under VRT practice. The present study used simulated rainfall and visualized the soil profile water distribution and path of VRT, subsoiling tillage (SS) and conventional tillage (CT) practices. Twenty-four hours after applying simulated rain, vertical soil profiles were photographed and staining features used to indicate the infiltration path and distribution of rainwater in the soil. Our results showed that when rainwater infiltrated into the soil, matrix and preferential flows occurred concomitantly under VRT practice, and mainly matrix flow for SS and CT practices. The VRT increased water infiltration into the soil, occurrence of preferential flow and water storage in the soil profile, while the soil of SS and CT somewhat hindered the infiltration of water. The VRT decreased soil bulk density (BD) by 9.2–10.3 % and increased soil saturated hydraulic conductivity (Ks) by 50.4–70.4 % compared with SS and CT. Moreover, VRT significantly increased potato tuber yield by 22.9–36.0 % compared with SS and CT in two consecutive years. Structural equation modeling (SEM) further revealed that VRT increased potato yield was mainly caused by decreasing BD and increasing Ks, and then increasing water storage in the soil profile. These findings suggest that decreased BD and increased Ks in VRT practice could be particularly important for infiltration, sustaining and supplying of soil water in rainfed areas worldwide, which is important for production practices in these areas.