The Impact Of Plastic Film Residue On The Soil And Water Environment Of Farmland And Its Comprehensive Effect Evaluation

Mulching technology had a good warming and moisture retention effect,could effectively regulate the field microclimate,improved crop yield,and was widely used in agricultural production.At present,the commonly used polyethylene mulch film was difficult to recycle and degrade,forming a large number of mulch film fragments remaining in the soil,there by changing the soil structure,hindering the absorption of water and nutrients by crops,and posing a serious threat to the sustainable development of agriculture.Biodegradable mulch film was considered one of the most promising alternatives to polyethylene mulch film,but it could not be completely degraded during the lamination period and entered the soil with farming practices.Therefore,clarifying the impact of biodegradable mulch film and polyethylene mulch film residues on soil,crops and environment could provide theoretical support for the promotion of biodegradable mulch film.At present,most of the research mainly focuses on the impact of mulch film residues on soil environment and crop growth,while there were relatively few studies on the possible greenhouse gas emissions and changes in global warming potential,and the mechanism was not clear.In addition,the comprehensive evaluation of the effects of mulch film residues on soil-crop-ecological environment needed to be further strengthened.In this study,two types of residual films,biodegradable residual film(BDRF)and polyethylene residual film(PERF),were selected for facility tomato as the research object,and different concentration gradients were set through pot control experiments,which clarified the response laws of soil physical and chemical properties,crop growth and development and cumulative greenhouse gas emissions to the types and contents of residual films,and clarified the comprehensive effects of mulch film residues on soil-crop-ecological environment systems.The main findings were as follows:(1)The influence mechanism of different residual film types and contents on soil physical and chemical properties was revealed.Biodegradable residual film and polyethylene residual film increased the bulk density of soil,and the increase rate of polyethylene residual film increased by 0.17%～0.45%compared with that of biodegradable residual film.The film residue hindered the vertical transport of soil moisture,which increased the average soil water content of 0～20 cm soil layer by 0.68%～38.01%compared with the non-membrane treatment,and decreased by 2.98%～49.11%in the 20～40 cm soil layer.When the residual film content≥720 kg/hm~2,the differences in bulk density and water content of the treated soil reached a significant level(p<0.05).Polyethylene residual film treatment had no significant effect on available phosphorus and soil p H.The biodegradable mulch film treatment significantly reduced the p H value by 0.27～0.74(p<0.05),and when the residual film content≥720 kg/hm~2,the available phosphorus content was significantly reduced by 25.31%～39.65%(p<0.05).(2)The response law of tomato growth index and water nitrogen use efficiency to different residual film types and contents was clarified.When the residual film content≤180kg/hm~2,the tomato root system developed well under the stimulation of the residual film,and the water use efficiency and nitrogen use efficiency of tomato increased by4.31%～5.08%and 1.58%～12.26%,respectively.When the residual film content reached1440 kg/hm~2,the water use efficiency and nitrogen use efficiency of tomato decreased by13.52%～18.09%and 10.83%～22.62%,respectively,reaching a significant level(p<0.05).Overall,the growth of tomatoes treated with biodegradable residual film was better than that treated with polyethylene residual film.(3)The impact of plastic film residue on global warming potential and its comprehensive effects on soil crop ecological environment have been explored.Biodegradable residual film increased the cumulative carbon dioxide emissions by0.68%～10.38%compared to the non film treatment,while polyethylene residual film decreased by 0.24%～12.70%.When the residual film content reached 1440 kg/hm~2,the residual film reduced the cumulative emissions of nitrous oxide and ammonia by10.77%～12.21%and 13.33%～13.59%,respectively,and reduced the global warming potential by 2.16%～5.91%.Moreover,polyethylene residual film landfill was less than biodegradable residual film landfill.Using factor analysis method,8 indicators representing soil effects,crop effects,and ecological environment effects were summarized into 2 main factors.The results showed that under the same residual film content,the overall performance of biodegradable film debris landfill was better than that of polyethylene film debris landfill;When the residual film content did not exceed 180 kg/hm~2,the comprehensive effect of plastic film residue was positive and performs better than the control group.When the residual film content was greater than 180 kg/hm~2,the comprehensive effect score of plastic film residue has been lower than the control group.In summary,the comprehensive effect of soil-crop-ecological environment system of mulch film residue was closely related to the type and content of residual film.When the residual film content≤180 kg/hm~2,the two residual films promoted crop growth,yield and nitrogen uptake,and the comprehensive effect of soil-crop-ecological environment was manifested as BDRF>PERF>CK.When the residual film content>180 kg/hm~2,the comprehensive effect of soil-crop-ecological environment was manifested as CK>BDRF>PERF.Compared to polyethylene residues,biodegradable residues have less negative impact on agroecosystems.The promotion of biodegradable mulch film in tomato cultivation in facilities in Northwest China can alleviate the negative effects of residual film pollution and promote the green and sustainable development of agriculture..