| Researchers are committed to developing biodegradable slow-release and controlled release organic fertilizers with aim of addressing issues such as low utilization efficiency of traditional chemical fertilizers and soil quality degradation caused by excessive application.Currently,one of the main slow-release fertilizers is urea-formaldehyde(UF)fertilizer.However,the nitrogen in UF fertilizers needs to be decomposed by microorganisms before being absorbed and utilized by crops.The release time is often long and difficult to meet the nitrogen demands of short-and medium-term crops.This paper aims to prepare an environmentally friendly biodegradable slow-release UF organic fertilizer which meets the nutrient demand patterns of short-and medium-term crops.Based on this,sucrose(SUC)modified UF fertilizer particles were prepared using a reactive extrusion granulation process.The process parameters were optimized,the composition and structure,degradation performance in soil,nitrogen nutrient release characteristics and the impact on plant growth of the prepared SUC/UF biodegradable slow-release fertilizer were analyzed.The research content and results of the paper are as follows:(1)SUC/UF organic polymer slow-release fertilizer particles were prepared by conventional reactive extrusion granulation process using raw materials including SUC,copper sulfate(catalyst)and hydroxymethylurea(MU).The optimum process parameters for the reactive extrusion were obtained through orthogonal experiments and single-factor optimization experiments;the structure of SUC/UF was characterized and analyzed using infrared spectroscopy(FT-IR),thermogravimetric analyzer(TG)and X-ray diffraction(XRD),and the preparation mechanism and nutrient release rate of modified UF slow-release fertilizer in still water were investigated.The results showed that there are strong hydrogen bonding interactions between the hydroxyl groups of SUC and the amide groups of UF molecular chains,which disrupte the hydrogen bonds between and within UF molecular chains and reduce the crystallinity of UF;In addition,the addition of SUC leads to the length of modified UF molecular chain smaller than that of pure UF molecular chain prepared by the same process and the distribution of molecular chain length wider.These effects affect the molecular and supramolecular structure of UF and have a significant impact on nitrogen release rate.(2)The effects of different raw material ratios of SUC/UF slow-release fertilizers on soil physicochemical properties,nitrogen content,plant root length,root weight,dry weight and yield were systematically studied through pot experiments.The experimental results showed that the nutrient release rate of SUC/UF was significantly faster than that of unmodified UF,which can effectively regulate soil p H,improve soil water holding capacity and permeability,thereby creating a more suitable environment for microbial growth,enhancing its biomass and enzyme activity,strengthening soil stability and promoting plant growth.Thus,the application of SUC/UF slow-release fertilizer can significantly increase plant nitrogen content,root length,root weight,dry weight and yield.The highest plant nitrogen content,root length,root weight,dry weight and yield were obtained by SUC/UF treatment with a sucrose addition of 10 wt%and a urea formaldehyde molar ratio of 1.4:1.0.The treatment significantly enhanced the root development of plants,making them stronger and absorbing more water and nutrients from the soil.The treatment also created the optimal growth environment by regulating soil physicochemical properties and enzyme activity,enabling plants to obtain more nutrient supply throughout the entire growth period,which is more in line with the fertilizer requirements of Brassica napus.Therefore,the yield significantly increased. |
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