Study On Biodegradable Polymer Materials With Both Water Absorption And Water Retention And Nutrient-controlled Release Properties

The widespread use of traditional agricultural materials containing nutrient elements not only leads to low material utilization,but also pollutes the environment.In order to solve these problems,slow and controlled release materials have been proposed,which has attracted widespread attention and has the advantages of improving material utilization,increasing crop yield,and reducing environmental pollution compared with traditional agricultural materia ls.At present,the slow and controlled release materials applied in agricultural production mainly include coated slow and controlled release materials and urea formaldehyde slow and controlled release materials.However,the coated slow and controlled release materials have the disadvantages of high production cost and difficult in biodegradation of the membrane material.Urea-formaldehyde slow and controlled release materials has better biodegradability,but it has a long nutrient release cycle and a single nutrient,which is often difficult to meet the fertilizer requirement cycle of the crop.And biodegradable polymeric materials is a new type of slow and controlled release polymeric fertilizer,which can control the release of nutrients under the action of microorganisms.It not only has good characteristics of nutrient slow release,but also can achieve complete biodegradation,which can reduce environmental pollution.However,their practical application effect,degradation mechanisms,and nutrient leaching losses have not been systematically studied.In this thesis,three kinds of biodegradable polymeric materia ls containing various nutrients developed by Shanxi Polymer Composites Enginee r ing Technology Research Center were studied.The practical application effect,biodegradatio n mechanism and nutrient leaching were studied by tomato pot experiment and soil column leaching experiment system,which laid a theoretical foundation for the practical application of biodegradable polymeric materials in agriculture.The specific research contents and results are as follows:?1?The biodegradable polymeric slow-release materials containing nutrient elements NPK?PSRF?,biodegradable polymeric slow-release material(PSRF+SAP_WS)which is simply physically mixed with PSRF and wheat straw-containing water absorbing resin(SAP_WS),PSRF and SAP_WS by chemical bonds to form a semi-interpenetrating network structure of water-absorbing and water-retaining biodegradable polymeric slow-release materials?SI-PSRF/SAPWS?,the effects of the structural properties of the three materials on their biodegradability and nutrient slow-release properties were studied by tomatoes pot experime nt.In this study,the scanning electron microscope?SEM?,Fourier transform infrared spectroscopy?FTIR?,X-ray diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?and other tests and characterization methods confirmed that the linear hydrophilic structure of PSRF itself is easily degraded by microorganisms or hydrolyzed,resulting in the worst slow release properties of nitrogen and phosphorus nutrients.For PSRF+SAP_WS,the degradation of SAP_WSS occurs only on the side chain groups and is more difficult to degrade,but it adsorbs the small molecules or ions released by PSRF degradation,thereby enhancing slow release properties of nitrogen and phosphorus nutrients in the entire system of PSRF+SAP_WS;The three-dimensio na l semi-interpenetrating network structure of SI-PSRF/SAP_WS not only attracts more microorganisms,promotes the degradation of SAP_WS,but also effectively control the release of nitrogen and phosphorus nutrients,and significantly improves its biodegradability and nutrie nt release properties.?2?Three types of biodegradable polymeric slow-release materials,PSRF,PSRF+SAP_WSS and SI-PSRF/SAP_WS,as well as the degradation mechanism and the properties of nutrient slow release,which have been studied in the tomatoes pot experiment.The difference of slow release of nutrients has different effects on soil and plant.Therefore,the effects of the three biodegradable polymeric slow-release materials on soil physical and chemical properties,microbiological properties,plant physiological characteristics and tomato yield and quality were further studied,and the correlation between these indexes was analyzed.The experime nta l results show that the application of different biodegradable polymeric materials can improve soil physical and chemical properties,improve soil enzyme activity,improve the tomato quality and increase the tomato yield to varying degrees.Among them,SI-PSRF/SAP_WS can more effectively improve soil moisture content,adjust soil pH?tend to 7.0?,regulate soil nutrie nt balance,increase soil organic carbon content,and improve urease activity,followed by PSRF+SAP_WS and PSRF.In addition,the physiological characteristics of plants treated with SI-PSRF/SAP_WS and tomato quality and yield were optimal,and the yield increased by 2.7 times,followed by PSRF+SAP_WS and PSRF,and the yield increased by 1.6 and 1.2 times,respectively.The above results show that the application effect of SI-PSRF/SAP_WS in the tomato pot experiment is the best.?3?The leaching loss of nutrients in three biodegradable polymeric slow release materia ls was investigated by soil column leaching experiments.The experimental results show that the treatment of different materials has a significant effect on the pH value and conductivity of the leaching solution.With the increase of the number of leaching,the pH value and conductivity first increase significantly and then stabilize.In addition,nutrient leaching loss increased first and then decreased in different material treatments.The order of nitrogen leaching in differe nt treatments was:PSRF>PSRF+SAP_WS>SI-PSRF/SAP_WS>CK;the order of phosphorus leaching was:PSRF>PSRF+SAP_WS>SI-PSRF/SAP_WS>CK.The difference in leaching loss of potassium in different material treatments was not obvious,which was attributed to the poor release effect of potassium.The above results indicate that SI-PSRF/SAP_WS can effectively reduce the amount of nutrient leaching loss,and further verify its better nutrient slow release properities,which can reduce the environmental pollution caused by nutrient leaching loss.