| It is a hot topic in the field of fertilizer research to prepare coated controlled-release fertilizers by using wide sources,low cost,renewable and environmentally friendly bio-based coating to replace petrochemical membrane materials with high cost and non-renewable materials.However,most of bio-based coated controlled-release fertilizers owns poor nutrient quality and single function,so it is very important to improve the controlled-release performance of the controlled-release fertilizers and develop multifunctional controlled-release fertilizer.This research used cotton straw as raw material,and the bio-based coated controlledrelease fertilizer was prepared.Then the hydrophobic and interpenetrating network technology was used to modify bio-based coating materials,which solved the bio-based material strong hydrophilicity,loose structure,the problem of large pore,and explore the mechanism of the modification technology to improve the performance of the controlled release.Then the fertilizer was applied to field corn,and the effects of application of controlled release fertilizer on corn yield and nitrogen nutrient uptake and utilization efficiency were investigated,which provided theoretical basis for application of bio-based controlled release nitrogen fertilizer on corn.Furthermore,in order to solve the problem of single function of bio-based coated controlled release fertilizer,a multifunctional double layer bio-based coated controlled-release fertilizer was prepared by using liquefied cotton straw and copper alginate,which can slowly release nitrogen,selenium and copper,and has antibacterial properties.To determine the quality,nutritional value and selenium utilization efficiency of cherry radish,the effects of multifunctional bio-coated controlled release fertilizer on the yield,quality,selenium content,nutrient utilization efficiency and rhizosphere microorganism of cherry radish were studied.The main results are as follows:（1）Cotton straw was used as raw material to prepare bio-based polyols,siloxane and polyether were used to modify bio-based polyurethane,and modified bio-based polyurethane coated controlled release fertilizers were prepared.The results showed that the nutrient release period of the modified coated fertilizer was extended from 2 days to 30 days compared with the unmodified bio-based coated fertilizer.This study revealed the mechanism of improving nutrient controlled-release performance by modifying bio-based coating:（1）The hydrophobic group of siloxane molecule grafted onto the bio-based polyurethane to improve the hydrophobic property of the coating and slows down the speed of water entering the coating shell.（2）Siloxane,polyether and polyurethane molecules cross-link to form an interpenetrating polymer network structure,which enhances the compactness of the bio-based polyurethane coating shell and reduces the amount of micropores and cracks on the coating shell;（3）The dense polyurethane structure immobilized part of the substances that did not participate in the coating formation reaction,avoiding the further increase of the coating shell pores,and allowing the continuous and slow release of nutrients.（2）The corn field experiments were conducted for 3-years to explore the effects of bio-coated fertilizers on maize yield and nutrient utilization.In this study,seven treatments were set up:no nitrogen fertilizer（CK）,and application of ordinary urea（U）,commercially available resin coated controlled release urea（PF）and self-made modified bio-based coated controlled release urea（BF）in full amount and 30% reduction,respectively.The results showed that compared with the total application of urea（U1）treatment,the average yield of corn under the total application of resin coated urea（PF1）and bio-based coated urea（BF1）treatment was 1.8% and2.1%,respectively.Compared with PF1 treatment,the yield of corn under BF1 treatment was0.4%.Compared with U,PF and BF treatments significantly increased the nitrogen content in maize grains,indicating that it was beneficial to the accumulation of nitrogen in maize grains.The PF and BF increased the average nitrogen uptake efficiency by 40.7%～59.5% and38.3%～69.5%,respectively,compared with U,indicating that controlled release fertilizer can improve the utilization efficiency of nutrients.Meanwhile,coated controlled release fertilizer can reduce the leaching of nitrate and ammonium nitrogen,and effectively reduce the nitrogen loss.（3）Using urea as the core,a double-coated controlled release fertilizer was prepared by using liquefied cotton straw to prepare bio-based polyurethane as the inner coating material and copper alginate gel as the outer coating material.A multifunctional bio-based coated controlled release fertilizer（DCRF）was prepared by modifying MSN@Se gel with mesoporous silica nanoparticles loaded with sodium selenate.The results showed that the nitrogen release period of DCRF reached 42 days,which was 1.4 times that of single-layer bio-based coated fertilizer.The selenium release cycle of DCRF was 40 times higher than that of quick-acting selenium fertilizer.The mechanism of DCRF to improve the controlled release performance of nutrients is as follows: on the one hand,when water enters the outer gel layer,it binds with the gel through hydrogen bond and is stored in the gel network,which slows down the speed of water entering the inner shell and thus delays the release of nutrients.On the other hand,mesoporous structures and positively charged groups on the surface of silica can adsorb negatively charged selenates,and the network structure of the gel shell increases the diffusion path of selenium,thus delaying the release of selenium.In addition,the fertilizer also has the function of slow release of copper,resulting in a durable anti-fungal ability,can inhibit the growth of Fusarium oxysporum Schltdl.（4）Potted experiment of cherry radish was carried out to verify the fertilizer efficiency and antibacterial performance of multi-functional fertilizer.The results showed that compared with normal fertilizer（UF）,sodium selenate（BF）and multifunctional coating fertilizer（DF）increased the yield by 59.02% and 170.30%,respectively,indicating that DF treatment could promote the growth and development of cherry radish and improve the fruit yield.DF treatment also increased the content of vitamin C and anthocyanin,decreased the content of nitrate,and improved the fruit quality.The selenium content of cherry radish fruit with multifunctional coating fertilizer increased by 4.8 times compared with that of available selenium fertilizer,and the selenium utilization efficiency of cherry radish fruit with DF treatment increased by 3.8times compared with that of available selenium fertilizer,which significantly improved selenium accumulation and nutrient utilization efficiency in fruit.Compared with other treatments,DF treatment significantly reduced the abundance of fungi in the substrate,which proved that the multifunctional coated fertilizer had a good inhibitory effect on fungi.In this study,cotton straw was used as raw material,and the dual-modified and multifunctional bio-based coated controlled release fertilizer was successfully prepared by modifying and functionalizing the coating material,which improved the controlled release quality of bio-based coating material and revealed its mechanism of action.In addition,the practical application effects of the two kinds of fertilizers on field corn and cherry radish were verified respectively,and it was proved that the two kinds of new fertilizers had the effect of increasing yield and improving nutrient utilization efficiency.This study fit with the requirements of sustainable agricultural development strategy,and can provide technical support and theoretical basis for the development and industrialization of green bio-coated controlled release fertilizers. |
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