| With the further implementation of the sustainable development strategy of agriculture,the disadvantages of the traditional non-degrad able plastic film,which once played an important role in increasing agricultural production and income,are increasingly exposed.and can no longer meet the requirements of modern agriculture for green environmental protection and resource conservation.Research and popularization of biodegradable mulching film is an inevitable measure to deal with "white pollution".However,biodegradable mulching film still has many problems,such as dependence on import of some raw materials,high production cost,disharmony between degradation cycle and plant growth cycle,etc.In addition,in order to solve the problem of low nutrient element utilization rate of common chemical fertilizers,more and more researchers turn their focus to the research of new high-efficiency chemical fertilizers.According to the above problem,in this paper,on the one hand,use simple convenient,low cost and easy to large-scale industrial production process preparation for gather adipic acid/butyl glycol terephthalate/urine aldehyde/starch(PBAT/UF/TPS)composite membrane,in promoting fat membrane integration and in solving pollution problems at the same time to reduce weight increase agricultural residues,etc.It is of great significance.On the other hand,the effects of different kinds of biodegradable polymer slow-release materials on soil physical and chemical properties,physiological characteristics and yield and quality of maize were studied.The specific research content and experimental results are as follows:(1)The PBAT/UF/TPS composite was prepared by in-situ reactive extrusion plasticizing process with starch(ST)modified by hydroxymethyl urea(MU)and biodegradable film 15-20μm thick was obtained by blow molding.Through the study of the microstructure of the preparation of membrane material and structure characterization,can be concluded that:in the form of solution to join the MU ST dispersed evenly in the system,the ST it is MU by in-situ reactive extrusion plasticizing capacity of mixing method is easy and PBAT,while at the same time of mixing can also make ST spherical structure is destroyed.The research on the preparation mechanism of the material shows that:Before extrusion,the urea formaldehyde(UF)reaction of precursor MU as raw materials mixed with ST,MU,small molecules fluid can easily enter the ST particles,significant damage ST of intermolecular and intramolecular hydrogen bonding,the plasticizing process not only can significantly improve the machining performance of ST,but also can make ST original rigid structure not be destroyed;When MU is extruded in a screw extruder,in situ polycondensation reaction occurs on the surface of ST particles to generate UF.The active groups on the macromolecular chain of MU can interact with the functional groups on the macromolecular chain of ST and PBAT,respectively,so as to plasticize and enlarge PBAT/ST composites.The mechanical properties of biodegradable mulch film prepared by this process have little difference between transverse and longitudinal,and are in line with national standards,which is suitable for large-scale production,The test results of biodegradation performance of plastic film materials showed that the degradation rate of PBAT/UF/TPS was increased due to the introduction of nitrogen components.PBAT/UF/TPS not only has excellent processing performance,mechanical performance and biodegradation performance,but also contains nutritional elements and is suitable for large-scale continuous production,which is conducive to promoting the development of biodegradable film industry,effectively improving resource utilization rate and promoting sustainable agricultural development.(2)The application effects of various biodegradable polymer slow and controlled release materials were studied by maize field experiment,and their effects on soil physical and chemical properties and plant physiological indexes were obtained.The results showed that:The application of biodegradable polymer slow and controlled release material can improve maize yield.Under the condition of ensuring normal plant development,the effect of annual precipitation on maize yield is greater than that of nutrient input.In two consecutive years of planting,the highest yield in 2020 was WRF,which reached 1207.53 kg/mu,148.49 kg/mu higher than conventional compound fertilizer.PRF had the highest yield in 2021,reaching 1144.80 kg/mu,77.23 kg/mu higher than conventional compound fertilizer,and WRF had the best grain quality.The input of organic matter is beneficial to increase the content of nutrient elements in corn grains.Studies on the effects of materials on soil properties showed that soil pH value did not change significantly,soil bulk density and soil specific gravity had the same trend,and the input of trace elements and organic matter could reduce soil bulk density and soil specific gravity.GRF with water-absorbing and water-retaining components has certain advantages in soil moisture content Soil microbial activity,ion concentration and ambient temperature all affect soil conductivity.The soil total nitrogen content decreased with the increase of soil depth,and increased at seedling and jointing stage,but decreased at heading stage,filling stage and maturity stage.The content of soil available P was relatively stable at seedling,jointing and heading stage,but decreased significantly at filling stage and maturity stage.Using correlation analysis and principal component analysis,the key indexes affecting maize yield were obtained:soil total nitrogen content,available phosphorus content,available potassium content,organic carbon content from 0 to 100 cm,and soil electrical conductivity from 20 to 40 cm at jointing stage and from 60 to 100 cm at maturity stage.In this study,the application and soil evaluation of biodegradable polymer slow and controlled release materials in maize field is beneficial to improve resource utilization rate and obtain higher grain yield,and carry out industrialization science and technology action and agricultural technology transformation while improving technical research,so as to improve the overall level of agricultural science and technology. |
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