Residual plastic mulch fragments effects on soil physical properties and water flow behavior in the Minqin Oasis, northwestern China

- Residual plastic film fragments (RPFF) in soil significantly altered the soil water distribution.
- Heterogeneous water infiltration slowly faded when equilibrium flow arrived.
- Water flowed along a preferential path, e.g., residual plastic mulch pieces in RPFF.
- RPFF reduced the matching degree of flow distribution region and maize root zone.

The covering of complete plastic films on soil would affect physical and biochemical properties of the soil microenvironment. Residual plastic film fragments (RPFF), which is left behind after retrieving the most of plastic films, could affect the flow behavior in the arable layer. This study was designed to assess the potential effects of RPFF on soil physical properties, water infiltration and distribution in the soil. Treatments with and without residual plastic film fragments (RPFF and NRPFF, respectively) were performed. A dye tracer was introduced to track the water movement, and the physical properties of the soil and the dynamic behavior of water transport in the soil column of the arable layer (0-20 cm) were determined. The initial gravimetric water content, bulk density, total porosity in 0-20 cm was significantly different between RPFF and NRPFF treatment. The dark blue area in maize root and densely rooted zones under RPFF decreased by 99% and 4%, respectively, relative to that under NRPFF. The sharply changing state of infiltration and outflow indicated that water flowed along a preferential path, e.g., macro-pores in NRPFF and residual plastic film pieces in RPFF. After clearing the RPFF, the time of equilibrium in 0-5, 5-10, 10-15, and 15-20 cm soil columns decreased by 48%, 50%, 49%, and 45%, respectively. Our results highlighted that the presence of RPFF significantly influenced soil physical properties, altered soil water distribution, and decreased the matching degree of the flow distribution region and the maize root (densely rooted) zone. The present study demonstrated that the importance of clearing the RPFF for irrigation water management in agriculture produces.