Effects Of Biodegradable And Ordinary Plastic Films On Maize Growth And Farmland Greenhouse Gas Emissions

The large emissions of greenhouse gases and the"white pollution"of film mulching are currently of widespread concern to the environment.It is estimated that the research and development of biodegradable plastics is one of the ways to solve"white pollution",and the application of biodegradable mulch film has been carried out in many places.Therefore,five treatments were designed:transparent ordinary plastic film mulching,transparent biodegradable plastic film mulching,black ordinary plastic film mulching,black biodegradable plastic film mulching and no film mulching as the control to explore the differences between soil,crop and greenhouse gas emissions in the ecosystems of maize farmland under biodegradable plastic film mulching and ordinary plastic film mulching.In this study,the effects of different types of plastic film mulching on soil moisture,temperature,and nutrients,maize growth status and greenhouse gases（CO₂,CH₄,N₂O）emissions were explored through a field fixed location experiment.From the perspectives of agronomic effects,economic benefits and environmental benefits,this study comprehensively evaluated the application effects of different plastic films in maize farmland.And the feasibility of biodegradable plastic film mulching replacing ordinary plastic film mulching was explored.The main findings are as follows:（1）Film mulching had a good thermal insulation and water retention effects.The plastic filn mulching increased the average temperature of the topsoil by 0.5 to 2.1°C and the water content of the topsoil increased by 7.5%to 13.8%during the whole growth period.Film mulching reduced soil water consumption in the early and harvest periods of maize and increased soil water consumption in the middle of growth.The ability of biodegradable plastic film mulching to increase temperature and moisture was between ordinary plastic film mulching and no plastic film mulching,and the ability of black plastic film mulching was significantly worse than that of transparent plastic film mulching.In addition,film mulching could significantly increase the nitrate nitrogen content of the topsoil soil by 21.3%to 37.6%,and the ammonium nitrogen content in the soil during the whole growth period had increased,while the accumulation of nitrate nitrogen had decreased,and the ordinary mulch film could effectively promote the absorption of nitrate nitrogen in the soil layer of 0-40 cm soil in maize during the jointing stage.（2）Film mulching could improve the dry matter accumulation and 100 grain weight of maize at the harvest stage,and significantly improve the yield and water use efficiency of maize.The grain yield and water use efficiency of black biodegradable plastic film mulching were the best,and the production and efficiency improvement of transparent biodegradable plastic film mulching was limited.In 2019,the yield and water use efficiency of transparent ordinary plastic film mulching,transparent biodegradable plastic film mulching,black ordinary plastic film mulching and black biodegradable plastic film mulching increased by43.3%,19.5%,41.0%,48.3%,53.1%,27.1%,56.1%,and 65.3%,respectively,and the yield and water use efficiency in 2020 increased by 22.1%,16.9%,21.0%,24.3%,23.9%,15.5%,27.2%,25.9%respectively.At the same time,the film mulching could improve the economic budget of maize,and the economic budget of transparent ordinary plastic film mulching,black ordinary plastic film mulching and black biodegradable plastic film mulching in 2019 had increased significantly by 64.2%,59.1%and 61.2%respectively compared with no plastic film mulching,and economic budget of transparent biodegradable plastic film mulching was not significantly different from no plastic film mulching.While in 2020,film mulching had not significantly increased the economic budget of maize because of the better yield income of no plastic film mulching.（3）Film mulching could significantly affect the total amount of soil CO₂ emissions,promote soil uptake of CH₄,and significantly reduce the emission peak to reduce the total emission of N₂O in farmland during the maize growing season.Soil temperature was the main factor affecting CO₂ and N₂O emissions,soil moisture was the main factor affecting CH₄uptake flux,and N₂O emission flux was also significantly positively correlated with the nitrate nitrogen content in the soil surface layer.Transparent ordinary plastic film mulching could significantly increase the total CO₂ emissions of maize season by about 13.8%compared with no plastic film mulching.Transparent ordinary plastic film mulching and black biodegradable plastic film mulching could significantly promote soil uptake of CH₄.Emissions during the peak N₂O period accounted for 50.7%to 82.8%of the total emissions during the entire growth period,and different types of mulching had no significant difference on N₂O emissions.Film mulching was an effective way for maize farmland ecosystem to reduce greenhouse gas emissions and increase economic benefits.Because of its significantly reduced GWP and significantly increased yield,plastic film mulching significantly reduced GHGI by 26.7%to63.7%,and there was no significant difference in GHGI between different types of plastic films.Except for the transparent biodegradable film mulching,the effect of increasing NEEB in the other plastic film mulching treatments were better.The significantly improved yield benefit of the transparent biodegradable film mulching cannot offset the extra cost caused by its high mulching film cost.NEEB was no different from no mulching.（4）Film mulching had a positive effect on maize cropland ecosystems.The comprehensive ranking of the application effects of various types of economic budget film mulching in maize fields was black biodegradable plastic film mulching>transparent ordinary plastic film mulching>black ordinary plastic film mulching>transparent biodegradable plastic film mulching in 2019,and black ordinary plastic film mulching>black biodegradable plastic film mulching>transparent ordinary plastic film mulching>transparent biodegradable plastic film mulching in 2020.The biodegradable plastic film mulching could also achieve the purpose of increasing production and efficiency,and even the comprehensive benefit was better than the ordinary plastic film mulching.The effect of transparent biodegradable plastic film mulching was not good.Therefore,from the perspective of agronomic effects,economic benefits and environmental benefits,the black biodegradable plastic film mulching had the feasibility of replacing the ordinary plastic film mulching,but the transparent biodegradable plastic film mulching still had a lot of room for progress in improving its degradation process.