Effects of plastic film residue and emitter flow rate on soil water infiltration and redistribution under different initial moisture content and dry bulk density.

Drip irrigation technology combined with film mulching has expanded rapidly in arid and semi-arid areas. Without sufficient mulch film recovery, large amounts of plastic film remain in the field, changing the original water infiltration movement, which is not well understood. In this study, structural equation modeling was used to study the impact of residual plastic film (RPF) and emitter flow rate (FR) on the migration time of wetting front (MTWF), soil infiltration aspect ratio (AR) and accumulative infiltration (AI) under different initial moisture content (IMC) and dry bulk density (DBD). The results showed that RPF prevented the downward movement of water, which led to increased MTWF, AI and AR. However, RPF had no direct effect on the AI and infiltration AR, and the effects that it did have on these factors were indirectly influenced by the MTWF. When the RPF content was greater than 480 kg/hm (with a mulching history of 26 years), the infiltration AR was greater than 1.0. Additionally, there was a parabolic relationship between the emitter FR and the MTWF. When the FR was 0.7 L/h, the MTWF reached its minimum value. Overall, this study explored the process of water movement under drip irrigation infiltration of RPF farmland and provided a theoretical basis for the design of drip irrigation systems for RPF farmland.