Effect of Plastic Film Residue on Vertical Infiltration Under Different Initial Soil Moisture Contents and Dry Bulk Densities

In arid and semi-arid regions, plastic film mulching can effectively improve crop yield, but with the increase of service life, a lot of residual plastic film (R-PF) remains in the soil. The application of a R-PF to a soil will alter soil moisture processes, and thus, affect the soil water distribution and its effectiveness. A quadratic regression orthogonal design was used to study the effects of initial moisture content (I-MC), dry bulk density (D-BD), residual plastic film content (R-PFC), and the burial depth of R-PF on the migration time of wetting front (M-F), moisture content (M-C), and accumulative infiltration (A(I)) of a test soil. It was found that I-MC, D-BD, and R-PFC were the main factors affecting M-C, M-F, and A(I), while the burial depth of R-PF had no significant influence. The order of influence for the factors affecting M-F was I-MC > D-BD > R-PFC, while the order of influence for the factors affecting M-C and A(I) was D-BD > I-MC > R-PFC. R-PFC was parabolic in relation to M-F, M-C, and A(I), when it was in the range of 50-100 kg/hm(2), while within the same range M-C and A(I) reached a maximum and M-F reached a minimum. The analysis of the interactive responses revealed that when the D-BD was greater than 1.29g/cm(3), the M-F initially decreased and then increased with the increase of R-PFC. When the R-PFC was more than 100 kg/hm(2), the M-F initially increased and then decreased with the increase of the D-BD. When the D-BD was larger than 1.31 g/cm(3), the A(I) initially increased and then decreased with the increase of R-PFC. It was apparent that the R-PF not only had a blocking effect on the wetting front, but also affected the water flow. When the R-PFC was between 50 and 100 kg/hm(2), the soil M-C was significantly increased. It was suggested that the R-PF pollution area should increase the mechanical recovery of plastic film, standardize the use and recycling of agricultural R-PF, optimize the planting model, and establish a recyclable model for the treatment of R-PF pollution, and it was proposed that the R-PFC remaining after recovery of the R-PF should be less than 50 kg/hm(2).This study can prove the law of soil water movement in the residue film pollution area and provide reference and solution ideas for the comprehensive treatment of residue film pollution in farmland.