Studies On The Preparation And Nutrient Release Characteristics Of Chitosan-coated Compound Fertilizer

Chitosan is a chitin's ramification without acetyl, it contains dissociative amido and its reactive ability is stronger than chitin's. Chitosan has special characters, such as innocuity, film-forming easily, favorable moisture absorption and biological tolerance ability and easy degaradation etc, so it has wide applied foreground in agriculture, industry, medicine, food, environmental protection and many other fields. As a kind of organic substance, chitin has large amount in nature, just less than cellulose's, and mostly rooted in shellfish. Zhejiang has abundance ocean resources, a large number of shirmps' or crabs' carapace are abandoned, if they cannot be dealt properly in time, not only would the environment be polluted , but also the carapace resources would be wasted badly. It also means the prospect of development of chitosan has great potential.Fertilizer was coated with membrane is a main way to control the nutrient release rate from fertilizer and increase using rate. But at present, the price of controlled release fertilizer is more expensive than others' because of the expensive coating material and complex technics etc, this baffles its application, developing and exploring new, cheap coating material will be a worthy research field in the future. In present paper, in order to make a new way to use chitosan and to develop a new fertilizer, chitosan which came from abandoned chitin, was used as main material to coat compound fertilizer and we produced seven different treatments coated compound fertilizers. To compare the effective difference of nutrient controlled release among these different treatments and uncoated compound fertilizer, this experiment used many kinds of evaluation methods such as water dissolution rate method, soil dissolution rate method, soil foster method, antibacterial test and pot experiment. These results showed that:1. Using AGS and CTS with two kinds of molecular weight of 300,000 and 2000 to prepare seven different chitosan-coated compound fertilizers, their film weight accorded with the requirement it should be 10%-30% of fertilizer's total weight.2. The results of water dissolution rate method showed that treatment 3 which the ratio oftwo kinds of chitosan's molecular weight of 300,000 and 2000 was 5:1 had best nitrogen controlled release effect, and treatment 5 had best controlled release effect in phosphorus and kalium .3. Soil dissolution rate and soil foster methods' results indicated that the nutrient release rate of chitosan-coated compound fertilizers with seven different treatments were all slower than uncoated compound fertilizer, it meant the chitosan-film had favorable controlled-release effect. Within 25 days , the cumulative N leaching content of the seven chitosan-coated compound fertilizers decreased differently by 7.93%-48.52%, the cumulative P leaching content decreased by 9.3%-50.5% differently,and the kalium had the similar trend . The controlled release effects of the treatment which the ratio of two kinds of chitosan's molecular weight of 300,000 and 2000 was 5:1 and another treatment using five times CTS inside than AGS outside were better than others.4. Seven chitosan-coated compound fertilizes were all more effective than uncoated compound fertilizer in inhibiting diameter of F. oxysporum f. sp. LycopersiciN Fusarium solani> Rhizoctonia solani. The antibacterial effect of treatments 3 , which the ratio of two kinds of chitosan's molecular weight of 300,000 and 2000 was 5:1, was best.5.The cabbages used chitosan-coated compound fertilizers grew better than those used uncoated fertilizer, the emergence rate of seedlings, outputs and content of Vc were all increased, at the same time the content of nitrate was reduced., in other words, the chitosan-coated compound fertilzer could improve cabbages' quality greatly. The differences of contents of nitrogen were greater than the differences of rapidly available phosphorus and kalium in soil among different coated treatments, it meant the chitosan-coated compound fertilizer had better controlled release effect in nitrogen than in phosphorus and kalium. The results of two kinds of fertilizers were different, it may be related to fertilizer's own character.