Preparation And Slow-release Characterization Of Coated Fertilizer With Modified Straw And Grease

With the massive application of chemical fertilizers and pesticides,soil contamination problems have become more and more serious,how to reduce the use of chemical fertilizers has become a hot academic researches,the coated fertilizer material with the biodegradable properties has not only the function of slow and controlled release,but also the bioremediation,and not causing any pollution for soil,so more and more researchers have been concentrated on the coated fertilizer material with the biodegradable properties.Waste straw by treatment or acetylation modification was made of a slow-release coating materials,and made slow-release coated fertilizer.The straw was treat by alkali and ultrasound.The best of ultrasonic power was420 W,the ultrasonic time was 0.5 h,alkali concentration was 8%at the 100?,the maximum amount of oil absorption was 1.58 g·g^-1.The optimum of processing straw coated was that the amount of processing straw was 15%?accounted for weight ratio of urea?,the coated time was 25-30 min,curing time was 20 min.Optimal conditions for straw's acetylation was that reaction temperature was 80?,reaction time was 2 h,the amount of catalyst was 0.06 g·g^-1,the amount of solvent and the mass ratio of straw was 1:1.The maximum amount of oil acetylation modified straw absorption was 1.88 g·g^-1.The optimum of processing straw coated was that the amount of processing straw was 10-12%?accounted for weight ratio of urea?,the coated time was 25-30 min,curing time was10-20 min.Infrared spectroscopy?FT-IR?,thermal gravimetric analysis?TG?,a specific surface area analyzer?BET?and scanning electron microscopy?SEM?were used to analyze and observe the structural processing changes of modified straw and coated fertilizer's film.FT-IR showed that functional group fully exposed after straw treat,1750 cm^-1was occurred around a strong absorption peak of C=O,at approximately 1750 cm^-11 C=O absorption peak intensitied and the shoulder around1050 cm^-1 were reduced,about 3500 cm^-1 and 3000 cm^-1-CH3 absorption peak decreased,stretching vibration of coated fertilizers'film reduced,which showed modified straw and grease had became the combination of interpenetrating networks.TGA showed that the modified straw and coated fertilizer's film was improved thermal stability,pyrolysis temperature increased,weight loss reduced.The surface area of modified straw and treatment straw was increased 12.62%and 16.95%compared to straw.SEM observed that modified straw internal was found pore structure and straw increased thickening after absorbing oil.Weight loss reduced,the degradation rate became slowed.SEM observed that modified straw internal was found pore structure and straw increased thickening after absorbing oil,film surface was relatively smooth,section was found sizes nutrient release channel,which showed it had sustained-release function.The oil absorption curve of alkali treatment's straw meet the quasi-second-order kinetic model from Lagergren adsorption model,R² was 0.999 and oil absorption rate constant was more than the unmodified straw.Particle diffusion model showed that internal structure of alkali treatment of straw was changed.The oil absorption curve of acetylated straw meet the quasi-second-order kinetic model greatly,which estimated theoretical saturation adsorption amount,particle diffusion model showed that adsorption rate of modified straw was increased.Nutrient release process of alkali treatment and acetylated straw coated fertilizer meet second-order kinetics and three kinetic models,nutrient release rate of alkali treatment straw coated fertilizer was more than the modified straw,which showed as the oil absorption increased,the slow release properties of straw increased correspondingly.The pot experiment indicated that corn plant fresh weight,ear weight of coated fertilizer had significant differences between other groups.Soil organic matter,total nitrogen,available nitrogen had obvious changes,and had significant differences.The nitrogen content of coated fertilizer's was increased gradually after30 d,and promoted the reproductive growth of corn,which showed that coated fertilizers had certain slowed release properties.In short,after alkali treatment and acetylated modification of straw,their oil absorption was increased to a certain extent,the two different coated fertilizers with grease had better slow-release properties than straw coated fertilizers.