| Low utilization rate of fertilizers and water shortage are two major factors which restrict the sustainable development of agriculture in China, how to improve the utilization rate of fertilizer and water becomes the key problem that need to be solved. Slow/controlled-release fertilizer of water-containing is a new type of fertilizer which can absorb water, hold water and slow release nutrient, achieving water-fertilizer controlling effects. In order to optimize the sustained release effect of slow-release fertilizer of water-containing, the paper based on the experiment factors of Chitosan’s(Chitosan,CS) molecular weight and concentration, the content of plasticizer and crosslinking agent, investigated that the properties of Chitosan membrane by changing these factors. Prepared CS coated urea which used three kinds of molecular weight of chitosan(chitosan’s molecular weight is 50000, 200000 and500000) as coating materials. Then, choosing 500000 molecular weight of Chitosan as inner coating materials, three kinds of Super absorbent polymer(Super absorbent polymer,SAP) P(AA-AM), P(AA-AMPS), P(AA-AM-AMPS) as the outer coating materials,prepared Super absorbent polymer-Chitosan(SAP-CS) double coated ureas. Studied the performance of these fertilizers through the determination of chemical and physical properties, dissolution rate method in water of 7days, and column-leaching in soil. The main conclusions were as follows:(1) The film-forming properties of chitosan were related to solution’s viscosity, the greater the relative molecular weight and concentration, the greater the viscosity of the solution.Concentration of chitosan was 2%, the molecular weight of 50000, 20 0000 and 500000 of the chitosan membranes showed good film-forming properties.Added polyvinyl alcohol and glutaraldehyde to the solution of chitosan could improve the performance of chitosan membranes, but the addition of glycerin couldn’t get the same result.When the concentration of chitosan was 2%(m/V), molecular weight was 500000, the dosage of polyvinyl alcohol was 0.85%(m/V), the dosage of glutaraldehyde was 0.5%(V/V),tensile strength, elongation at break and swelling degree of chitosan membranes all showed good performance, and that were the optimum process conditions for preparing chitosan membranes. By this time, tensile strength, elongation at break and swelling degree of chitosan membrane were 39.5MPa,52.3% and 6.85%, respectively.(2) Molecular weight of chitosan, glutaraldehyde, paraffin and polyvinyl alcohol influenced the slow release performance of the CS coated urea obviously. When the molecular weight of the chitosan was 500000, coated amount was 3%, the sealant dosagewas 20%, the dosage of PVA was 0.85% and the dosage of glutaraldehyde was 0.5%, the characterization of CS coated urea showed best effective. At this point, the primary dissolution rate of CS coated urea was 68.38%, cumulative dissolution rate in seven days was 76.40%.(3)This paper prepared SAP- CS double coated urea on the basis of the CS coated urea.Using the P(AA- AM) as outer membrane, the amount of chitosan coated, paraffin, surface crosslinking agent and adhesives were optimized. The molecular weight of chitosan was500000, coated amount was 3%, coated amount of the outer membrane P(AA- AM) was10%, water as adhesive, the dosage of surface crosslinking agent was 10% and in the absence of paraffin. At the moment, the primary dissolution rate of SAP- CS double coated urea was 39.8%, cumulative dissolution rate in seven days was 68.59%.(4) SAP-CS double coated ureas behaved high water-fertilizer controlling effects.Dissolution rate in water showed that the different coated quantity of SAP- CS double coated urea’s nitrogen release rate and the bibulous rate were better than the SAP coated urea in different levels, with the increase of the amount of coated, the effect will be more apparent.The primary dissolution rate of SAP- CS double coated ureas were between 38.9% and56.57%,cumulative dissolution rate in seven days were between 75.78% and 94.11%.Bibulous rate increased by 4.14%-19.21%, primary dissolution rate was reduced by22.55%-25.74%, cumulative dissolution rate in seven days reduced by 5.87%-16.58%.The slow releasing nutrients of SAP- CS double coated ureas in the soil were similar to the rules in water, but the slow-release effect was more prominent in the soil. Comparing with the normal urea, nitrogen accumulated leaching rate of the super absorbent polymer mixed with urea, SAP coated urea and SAP- CS double coated urea were reduced by 7.76%- 9.23%, 7.76%, 22.99%, 13.47%- 29.59%.Among all the fertilizer treatments, P(AA-AM-AMPS)’s release properties and water-fertilizer controlling effects were better than P(AA-AM) and P(AA-AMPS)’s。... |
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