Effects Of PBAT Biodegradable Plastic Film On Soil Nutrients And Microbiological Properties

Since the 1970s,mulching technology has experienced rapid development in China,which has greatly increased crop yields.However,due to the large amount of plastic mulch remaining,it has caused serious pollution to the soil environment.As a kind of environmental protection mulch,biodegradable mulch is more and more widely used in China.In this study,polyadipate-butylene terephthalate(PBAT)biodegradable mulch film was used as the research material.The degradation characteristics of the biodegradable mulch film under different soil moisture conditions were analyzed based on indoor cultivation,and then the different PBAT film was analyzed based on pot experiments to study the effects of the amount of biodegradable plastic film added on the soil environment,microbial community structure and tobacco quality.Finally,field experiments were conducted to study the effects of different PBAT biodegradable plastic film cover on soil properties and tobacco yield and quality.For the culture test of biodegradable mulch responding to water conditions,three PBAT biodegradable mulches and one conventional polyethylene mulch were selected,and three gradients of soil water content were set:15%,25%and 35%.The results showed that the biodegradable mulch with PBAT as the main component can be degraded after being added to the soil.Scanning electron microscopy images showed that the biodegradable mulch has a large number of microscopic pores after 180 days of cultivation,and the carbonyl index also increased with the degradation time.Under the condition of 25%soil water content,the degradation rate of various biodegradable mulch films was the fastest,which was significantly better than the soil water conditions of 15%and 35%(P<0.05).Among the different biodegradable mulches,Ecol mulch has the fastest degradation rate,showing the trend of Ecol>Eco2>Eco3>PE mulch.The change law of soil microbial activity is consistent with the degradation rate of the plastic mulch,indicating soil moisture affect the degradation of biodegradable mulch by affecting soil microbial activity.For pot experiments with different amounts of biodegradable mulch,the biodegradable mulch was set to 0 g·kg-1(CK),0.05 g·kg-1(T1),0.5 g·kg-1(T2),5 g·kg-1(T3)4 additions,PE mulch addition is 0.05 g·kg-1.Tobacco and soil samples were collected at the rooting stage(30 days),the long-term growth period(60 days),and the bud stage(90 days).The results showed that compared with CK,the addition of PBAT biodegradable mulch significantly increased the root vitality of tobacco at the early stage of growth,and had no significant effect on other indicators;when the tobacco was in the prosperous period,when the amount was 5 g·kg-1,the biodegradable mulch remained significantly affected the development of tobacco root system and had no significant effect on other indicators;adding biodegradable mulch after tobacco maturation significantly increased the leaf area and stem circumference of the tobacco plant,and increased the potassium content in the tobacco rhizome,but had no significant effect on tobacco quality.As the amount of biodegradable mulch added increases,the activity of related antioxidant enzymes in tobacco leaves has increased.The addition of biodegradable mulch film significantly increased the content of soil available potassium in the early stage of tobacco leaf growth,but it had a certain inhibitory effect on soil pH and organic matter content.After degradation of biodegradable mulch film,the soil pH and organic matter content increased.With the increase of the amount of biodegradable mulch,the overall performance is that the physical and chemical indicators of T3 treated soil have the largest improvement.In addition,the addition of biodegradable mulch film improved the soil microbial community structure,the proportion of Proteobacteria increased,and the activity of soil-related enzymes increased significantly.For field trials covered by different biodegradable mulches,three types of PBAT biodegradable mulches(Eco1,Eco2,Eco3),ordinary polyethylene mulch(PE),and uncovered film treatment(N)were set.The test results showed that the biodegradable mulch can be degraded under field conditions,and there was almost no residue after 150 days.Among them,the degradation rate of Ecol and Eco2 mulch is faster than that of Eco3,and there is no change before and after PE mulching.Biodegradable plastic film mulch has no significant effect on tobacco agronomic traits,but due to the rapid degradation of Ecol and Eco2 treatment,it can't meet the temperature and moisture requirements of flue-cured tobacco during the growth process,affecting the quality of flue-cured tobacco.At the mature stage of tobacco,biodegradable film mulching significantly reduced the content of total nitrogen and available potassium in the soil compared with PE treatment,but delayed the process of soil acidification,increased soil pH,and improved the microbial structure in the soil,which improved soil FDA hydrolase activity.In summary,water conditions can affect the degradation of biodegradable mulch,and the degradation rate is the fastest under 25%soil water conditions.Exogenous addition of biodegradable mulch has no effect on the quality of tobacco leaves.With the increase of the amount added,the activities of related antioxidant enzymes in tobacco leaves have been improved.In addition,the addition of biodegradable mulch changed the soil microbiological properties and increased the activity of soil-related enzymes.However,in the field test,biodegradable mulch inhibited the quality of tobacco production to a certain extent,so more attention should be paid to the thickness of the mulch and the ratio of materials,so that the mulch began to degrade in the middle and late stages of tobacco growth,to avoid affecting the yield of flue-cured tobacco.This experiment provides a good scientific basis for the practical promotion and application of biodegradable plastic film tobacco fields.