Effects of different management practices on vertical soil water flow patterns in the Loess Plateau

- Preferential flow was triggered by wetting front instabilities in uncultivated land.
- Macropore flow was confined into two isolated patches in conventionally tilled soil.
- The alfalfa taproot in the alfalfa field resulted in high and continuous preferential flow.
- Conservation tillage shaped the preferential flow into an inverted triangular distribution.

Different management practices are adopted to ensure sustainable development in agriculture and to maintain ecological environment security. However, the soil water infiltration types under different management practices were still unclear. This study was designed to assess the effect of different management practices on the water flow behavior of soil. Four management practices were carefully selected. Plot 1 was uncultivated field, Plot 2 contained alfalfa (Medicago sativa L.) and was untilled for two years (alfalfa field), Plot 3 contained maize (Zea mays L.) with conventional tillage from 2008 to 2015 (conventional tillage field), and Plot 4 contained maize with conservation tillage from 2008 to 2015 (conservation tillage field). Soil physical properties (e.g., gravimetric water content, soil bulk density, total porosity, and saturated water content) in the top 50 cm layer were measured following conventional methods A dye tracer was introduced to these plots, and the different types of water flows were visualized using classified dye-stained patterns. In the uncultivated field, preferential flow was triggered by wetting front instabilities and generally confined to the upper 15 cm of the soil profile. The presence of preferential paths (alfalfa taproot) in the alfalfa field resulted in high and continuous preferential flow. The macropore flow bypassed the compacted soil and was confined into two isolated patches, making it the dominant flow behavior in the conventional tillage field. Conservation tillage systems enhanced the continuity and connectivity of the macropore system and converted the shape of the preferential flow to an inverted triangular distribution. The order of continuity and connectivity degree for the macropore system from highest to lowest was alfalfa field, conservation tillage field, uncultivated field, and conventional tillage field. Above mentioned results that were newly achieved from this study highlighted a significant change in soil water storage and flow behaviors with different management practices compared with those of uncultivated land. The present study suggests that local governments and farmers would prefer alfalfa field and conservation tillage field to other management measures.