Study On Structure Regulation And Properties Of Urea Aldehyde Biodegradable Slow And Controlled Release Fertilizer

In order to solve the problem of low utilization rate of traditional chemical fertilizers and the degradation of soil quality caused by excessive use,more and more researchers began to pay attention to the research and development of biodegradable controlled release materials based on high utilization rate and can improve soil fertility.However,there are few studies on biodegradable slow and controlled release materials that can meet crop nutrient requirements and improve soil quality at the same time.In view of the above problems,this paper,on the one hand,prepared straw modified urea aldehyde slow and controlled release fertilizer with different modification methods,and analyzed their composition and structure.In addition,soil culture experiments were carried out to study the effects of different modification methods and C/N ratio on the degradation performance of biodegradable polymer materials,the release characteristics of C,N and P,and the effects on soil nutrients content.On the other hand,five different types of biodegradable slow-release fertilizers were selected,NPK urea aldehyde group slow controlled release fertilizer（PSRF）,NPK silicon urea aldehyde group slow controlled release fertilizer（GSRFEx）,NPK urea aldehyde group semi-interpermeable polymer network slow controlled release fertilizer(SI-PSRF/SAP_CS)with water absorption and water retention function,and two commercially available slow controlled release fertilizers（S-UF containing nitrogen nutrients and S-CRF containing nitrogen,phosphorus and potassium nutrients）.The rules of nitrogen and phosphorus nutrient release and leaching loss were studied by leaching loss experiment of wheat.The specific research contents and results are as follows:（1）Through soil culture experiments,the degradation rate,carbon,nitrogen and phosphorus release characteristics and the effects on soil nutrient content of PSRF,straw（CS）,straw after high temperature alkali cooking（PTCS）and straw modified slow-release and controlled-release fertilizer（CS/PSRF,PTCS/PSRF,CS/UF,CS and PSRF simple mixture（CS+PSRF））were studied.The characterization and test results of Fourier transform infrared spectroscopy（FTIR）,thermogravimetric analyzer（TG）and X-ray diffraction（XRD）show that the high-temperature alkali boiling treatment of straw can effectively remove hemicellulose and lignin;Compared with CS+PSRF,CS/PSRF,PTCS/PSRF,and CS/UF,form hydrogen bonds between CS or PTCS and PSRF or UF,which can greatly reduce the crystallinity of each component of the material.The results of soil culture experiment showed that the degradation rate and degree of biodegradable polymer materials were improved,and CS/PSRF was the best.For CS/PSRF system,CS/PSRF with C/N ratio of 2.5:1 is more suitable for microbial energy,and has the highest degradation rate and the greatest contribution to soil humification.The application of different straw modified slow-release and controlled-release fertilizers can improve the content of soil nutrients,convert more carbon released by straw degradation into soil carbon and improve soil fertility.The application of different straw modified slow and controlled release fertilizers could increase soil nutrient content and convert more carbon released by straw degradation into soil carbon,thus improving soil fertility.（2）The nitrogen and phosphorus nutrient release and leaching loss of PSRF,GSRFEx SI-PSRF/SAP_CS,S-UF and S-CRF were studied by wheat leaching loss experiment.The results showed that the cumulative nitrogen nutrient release rate of five kinds of slow and controlled release fertilizers was over 55%,and the cumulative nitrogen nutrient leaching loss accounted for more than 10%of the cumulative release amount.At the same time,the cumulative release rate of phosphorus in the four slow and controlled release fertilizers was over 85%after 30 days,and the cumulative leaching loss of phosphorus in the four slow and controlled release fertilizers accounted for about 10%of the cumulative release amount,and the leaching loss rate was low.