| The environment-friendly film with nutrient slow-release effects is now the key point of the research about the coated slow-release fertilizers.The sisused polyvinyl alcoholand polyvinyl pyrrolidone as the raw materials,biochar as the filling agent,and according to the theory of organic polymer copolymerization and solution blending technology to produce water-based copolymer-biochar composite coating materials and coated urea.We studied the appropriate modification conditions by testing the water absorbency,the water permeability and the permeability of ammoniummeans of the water-based copolymer-biochar films,and the modification and degradation mechanism were analyzed using scanning electron microscopy,infrared spectroscopy and buried soil test.Meanwhile,the microstructure and the nitrogen release characteristics of the coated urea under different processing were studied by the infrared spectrometry,the scanning electron microscopy(SEM)analysis and the soil column leaching.Besides,the field experiments were used to validate the selected coated urea fertilizer.The results of the study are as follows:(1)Adding the biochar made of different materials(such as maize straw,rice straw(S)(Y),surface litter(K))could reduce the absorbency of film materials;three processings were screened out according to its permeability,the infrared spectrum and the biodegradability,namely maize-based biochar was 3%.the concentration of the water-based copolymer was 6%,the particle size of biochar was 60 mesh(Yl),rice-base biochar was5%,the concentration of the water-based copolymer was 8%,the particle size of biochar was 200 mesh(S5),litter-based biochar was 7%,the concentration of the water-based copolymer was 8%,the particle size of biochar was 60 mesh(K6).The absorbency rate of the three kinds of preparation of water-based copolymer was reduced by 27.89%,28.19%and 26.00%,respectively,the degradation rate after 120 d reached to 32.44%,32.94%,32.44%,and with the increase of time buried soil degradation rate will further increase,which will not cause secondary pollution to the planting soil.(2)The results of scanning electron microscopy(SEM)showed that the water-based copolymer-biochar composite film materials can mix evenly and distribute completely on the fertilizer particle surface;at the same time,part of the coated materials permeated into the gap of the surface of the urea particles,which made the film materials and urea combine more closely,formed a barrier for water molecules to enter into the coated urea,and extended its slow-release performance.(3)The soil column leaching test results showed that it is best for the coated fertilizer slow-release effects with 5%of the rice-based biochar,8%of the concentration of the water-based copolymer and 200 mesh(S5)of the particle size of biochar,which had a long slow-release period,and after 22 d,accumulated release rate of N was 65.28%.(4)The results of the fertilizer efficiency of maize field showed that when the usage of the water-based copolymer-biochar composite coated urea had been reduced by 20%,there was still about 1.45%of production.All in all,the water-based copolymer-biochar composite coated material made of polyvinyl alcohol,polyvinyl pyrrolidone and biochar has the stronger degradability in the soil,which won’t cause pollution to the planting soil.Meantime,the water-based copolymer-biochar composite coated urea has a good effect on slow-release and yield increasing.Thus,the environment-friendly film materials and coated urea can be prepared according to the requirements. |
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