Degradation Of Polymer Coating Residual Of Controlled Release Fertilizer And Its Effects On Soil Biological Properties

The efficiency of fertilizer have been improved evidently, loss and volatilization of nutrition elements have been reduced, waste of resources have been lightened, product quality and crop output have been enhanced markedly by applied controlled-release fertilizers, so many experts think highly of them. The production and use of controlled-release fertilizers are one of the main trends for the development of chemical fertilizers at present, and are necessary need for the development of modern agriculture and sustainable development strategies. Controlled-release fertilizers application , polymer coating residual of controlled release fertilizer will be left in the soil .With the development and application of controlled-release fertilizers, polymer coating residual of the degradation studies and biological effects in the soil environment (plants, animals, microorganisms) should be regarded. The objective of this study was to offer advice and theory proof for controlled-release fertilizers research and using.Degradabilities, product and degradation mechanism of polymer coating residual of controlled release fertilizer were investigated by using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), viscosimetry and gas chromatography-mass spectroscopy (GC-MS). Cole and maize potted experiment and together with method of chemical analysis have been used in the paper. The purpose of this paper was to study effects of polymer coating residual of controlled release fertilizer on soil physical, chemical and biological property and biological effects on cole and maize. Meanwhile, the use of earthworm test, evaluated on the biological effects of polymer coating residual of controlled release fertilizer of earthworms from the biochemical aspects. The main results were summarized as follows:1. Controlled release fertilizer coating residual was photodegradable. Controlled release fertilizer coating residual under UV irradiation, photo-oxidative decomposition, promote oxidation of the carbon chain fracture PE gradually generate organic acids. With increasing the degree of degradation, the carbonyl index and crystallinity of polyethylene in Coating increased, but the melting point and relative molecular weight of polyethylene in Coating decreased. Some low molecular weight products, such as alkyl hydrocarbon, ketone, aldehyde, ester, carboxylic acid and binary carboxylic acid were detected in the degraded Coating. The coating residual containing starch was degraded much more rapid than non-starch coating residual under UV irradiation. Therefore, the starch as an additive can significantly improve the degradation rate of controlled release fertilizer coating residual.2. Controlled release fertilizer coating residual in the natural exposure illumination, with the increase of irradiation time, the results of infrared spectra showed the carbonyl peak intensity increased. The main reason was the existence free radicals after exposure under of starch .The role of these free radicals in the polyethylene main chain to long chain was broken, and the occurrence of new and more free radical further light polyethylene chain degradation. In this reaction, while oxygen in the air can enter into the gap in the blends, oxygen and reaction of polyethylene chains to produce free radicals, these free radicals generated after photo-decomposition of carbonyl, vinyl, etc. group. The study found that the higher starch content, the degradation of polyethylene in promoting the greater, it illustrates the presence of starch mixture while also contributed to the gap increases, the oxygen into the mixture which is easier, resulting in a corresponding increase in free radicals.Therefore, with the illumination time increases, the performance results of IR carbonyl peak intensity was increased.3. The results of potted cole experiment showed that controlled release fertilizer coating residual could reduce soil bulk density, increased soil total porosity. So aerated status of soil has been improved and loose soil increased the aerated and dank character of soil. The contents of chlorophyll , height of cole, number of leaves, fresh mass and growth potential of the cole had been increased by controlled release fertilizers coating residual. The result that the total N and total P of the cole were not changed obviously indicated that the absorption of N and P had not produced adverse effects. The total K of the cole had been increased by controlled release fertilizers residual coating. Controlled release fertilizer coating residual applied to the soil on catalase, urease, invertase, phosphatase activity was not significantly affected.4. The results of potted maize experiment showed that within a certain range, controlled release fertilizers coating residual was applied to increase the amount of corn growth potential, plant height, chlorophyll and yield of maize have increased. Controlled release fertilizers coating residual was better than the yield of corn processing blank and only the fertilizer treatment. Number of rows in the corn ear, kernels per row no apparent increase in cases, the grain weight had increased significantly, indicating controlled release fertilizers coating residual late in the growth of maize, namely, filling to provide sufficient nutrients to ensure corn filling the need to increase production. Controlled release fertilizers coating residual applied to the soil of the maize catalase, urease, invertase, phosphatase activity was not significantly affected.5. Controlled release fertilizers coating residual earthworm soil tests showed that in the period of this experiment, different amounts of controlled release fertilizers coating residual treated soil, the earthworm enzyme, catalase and superoxide dismutase were no significant impact.6. The degradation experiment of thermoplastic coating residual of controlled release fertilizer under soil incubation environment indicated that controlled release fertilizer coating residual was degradable. The coating residual containing starch was degraded much more rapid than non-starch polyethylene coating under soil incubation environment. With increasing the degree of degradation, the carbonyl index and crystallinity of polyethylene in coating residual increased, but the melting point and relative molecular weight of polyethylene in coating decreased.7. The degradation experiment of thermoplastic coating residual of controlled release fertilizer under irradiation and soil incubation environment indicated that degradation mechanism of controlled release fertilizers coating residual was free radicals mechanism. Potted plants experiment showed that biological effects on soil environment such as plant, animal and soil enzyme was safe. Overall, controlled release fertilizers residual coating was no significant impact on soil environment.