Preparation And Application Of Amino Acid Urea-Formaldehyde Biodegradable Slow-Release Materials

China is the world’s most populous country,accounting for about 18% of the world’s total population.However,only 7% of the world’s arable land,so chemical fertilizers are essential in ensuring food security in China.However,the massive application of chemical fertilizers has also led to severe environmental pollution.Therefore,improving the efficiency of fertilizer utilization,reducing environmental pollution,and developing a sustainable agricultural system are common concerns of researchers today,and one of the main ways to solve this problem is to develop biodegradable slow and controlled-release fertilizers.Slow and controlled release fertilizers can control the rate of nutrient release,improve the efficiency of fertilizer utilization,reduce environmental pollution caused by nutrient loss,reduce agricultural costs,and ensure crop yield,which is of great significance to the sustainable development of agriculture.In this thesis,amino acid urea-formaldehyde(UF)as the substrate,raw powder of amino acid from biomass resources,and ferrous sulfate as raw materials were used to obtain amino acid urea-formaldehyde biodegradable slow and controlled release fertilizer by reaction extrusion preparation process.The effects of the prepared slow-release fertilizer on nutrient release and degradation,soil physical and chemical properties,and plant growth were systematically investigated.The details and results of the study are as follows:(1)The amino acid urea-formaldehyde biodegradable slow-release fertilizers AARP-UF and AARPFe-UF with semi-interpenetrating network structure were prepared by a reactive extrusion process using amino acid powder(AARP)and ferrous sulfate(Fe SO4)as raw materials and orthogonal and single-factor optimization experiments obtained the optimum process parameters.The structures of the fertilizers were characterized by infrared spectroscopy(FT-IR),X-ray diffraction(XRD),and thermogravimetric(TG)analytical tests;the surface morphology of the fertilizers was observed by scanning electron microscopy(SEM),and the compression strength and nitrogen nutrient release rate in still water were determined.The results showed that introducing AARP and AARPFe disrupted the crystal structure of UF molecules and formed a semi-interpenetrating network structure through solid hydrogen bonding interactions with UF.The crystallinity of the three slow-release fertilizers,UF,AARP-UF,and AARPFe-UF,was 67.94%,59.28%,and 57.46%,respectively,and the compressive strengths were 1.64 MPa,3.01 MPa,and 4.06 MPa,respectively,3.01 MPa and4.06 MPa.The initial nitrogen release rates of AARP-UF and AARPFe-UF in still waters were 18.6% and 14.9%,respectively,significantly lower than the initial nitrogen release rate of UF of 24.8%.The three slow-release still-water fertilizers’ cumulative 90-day nitrogen nutrient release rates were 76.3%,36.7%,and 32.7%,respectively.It showed that introducing AARP or AARPFe could significantly reduce the crystallinity of UF,increase its compressive strength and improve its nitrogen nutrient slow-release performance.In addition,the improvement effect of AARPFe was more evident than AARP’s,and the prepared slow-release fertilizer AARPFe-UF had better performance.(2)The soil nutrient release performance,degradation rate,and effects on soil physicochemical properties,oilseed rape biomass,and yield of amino acid urea-formaldehyde biodegradable slow-release fertilizer were systematically investigated by oilseed rape potting experiments.The experimental results showed that the nutrient release performance of amino acid urea-formaldehyde biodegradable slow-release fertilizer was significantly improved.Its nitrogen release rate was much higher than that of UF.The addition of amino acids changed the orderliness of the molecular chains of urea-formaldehyde UF,which played a specific role in regulating the nutrient release in the fertilizer.The physical and chemical properties of the soil are also significantly affected,which can significantly adjust the p H of soil acidity and alkalinity and return the p H of the soil to neutral,and also improve the electrical conductivity and total nitrogen level of the soil,resulting in higher ion concentration,higher fertility,and higher quality.In addition,it has a promoting effect on crop growth and development,which can increase the root length and biomass of rape to different degrees and then increase the yield of rape.