EFFECTS OF LONG-TERM FILM MULCHING ON THE CHARACTERISTICS OF SOIL RESIDUAL FILM IN TOPSOIL LAYER OF MAIZE PLANTED IN NORTHERN CHINA

The wide utilization of mulch-film brings great economic value but also causes "white pollution" in China. Based on the investigation and study on the distribution characteristics and influencing factors of soil plastic film residue in the typical maize planting area in Hebei and Inner Mongolia of China, the present situation of residual pollution in the system of maize planting field was accurately evaluated, and the scientific basis was provided for the proposal of prevention and control measures of residual pollution in this area. In this study, the amount and abundance of plastic film residues in different topsoil layers were investigated and analyzed in 21 farmlands with different years of plastic film mulching and no plastic film mulching fields as the control. The results showed that the amount of soil residual film was 4.04~314.73kg.hm-2 in topsoil soil of maize planting area, and 60.91% of the plots exceeded the national standard, therefore, the soil residual film pollution of maize cultivated layer in this area was serious. The amount and abundance of residual film in topsoil soil of maize planting area was increased with the increase of the years of film mulching. However, the amount and abundance of residual film was decreased gradually with the increase of soil layers. The amount and abundance of residual film distributed in the 0~10cm soil layer was significantly higher than that in the 10~20cm and 20~30cm soil layers. The residual film showed a downward trend to the deep soil with the increase of the plastic film mulching years. With increase of the plastic film mulching years, the abundance and ratio of residual film in small and medium size of soil layer (0~30cm) continuously decreased, and the small residual film < 4cm2 in 20~30cm soil showed an obvious increasing trend, which increased the difficulty of the recovery of residual film in long-term plastic film mulching farmland, and may have a long-term impact on the soil environment of topsoil. Therefore, appropriate measures should be taken to increase the recycling of plastic film and reduce the pollution of plastic film in this area and play a positive role in protecting the health of maize planting area in Hebei and Inner Mongolia.