Study On Preparation And Controlled-release Properties Of Compound Coating Agent For Controlled-release Fertilizer

Proposing national efforts to promote a resource-conserving, environment-friendly society requirements, slow/controlled-release fertilizer instead of conventional fertilizer became an irresistible trend. Slow/controlled-release fertilizer could not only slow down or control nutrient release rate, coordinate the supply of crop nutrients with crop nutrient needs, reduce nutrient loss and frequency of application, but also avoid soil compaction, conducive to promoting the industrial restructuring, to achieve the value-added of agriculture, increasing efficiency and increasing income of farmers. Slow/controlled-release fertilizer became an important trend in the21century.The inexpensive biodegradable polymer resins were used as the main raw materials and formulated with emulsifier, plasticizer and others, employed the polymer composite film and controlled-release technology, used the composite film former instead of the operational single film former. By single factor and orthogonal experiments to explore the method of preparing coating agent for controlled-release fertilizer, looking for relatively simple production and coating process, the compound coating agent for controlled-release fertilizer which applied to coat ordinary granular fertilizers was researched. The controlled-release properties and physico-chemical properties were further determined to provide a scientific basis for the preparation, performance evaluation and application of coated controlled-release fertilizers used in field crops. The main conclusions were as follows.1. The single factor and orthogonal experiments results showed that, the preparation conditions of the compound coating agent for controlled-release fertilizer KSFBJ:the optimal dosage of resin BX was8.4%, resin JC was5.6%; T-80was the emulsifier, the optimal dosage was1.55%; vegetable oil was the plasticizer, the optimal dosage was1.00%; rhodamine was the pigment, the optimal dosage was0.10%; ethyl acetate was the solvent, the dosage was83.35%.2. The controlled-release properties of compound coating agent for controlled-release fertilizer results showed that, the initial dissolution rate of coated fertilizer A and B were reduced significantly through using the compound coating agent for controlled-release fertilizer to coat the ordinary fertilizer A and B, preventing the loss of fertilizer nutrient and environmental pollution caused by the disposable excessive release of the early fertilizer. The initial dissolution rate of the coated fertilizer A and B were less than15%, the cumulative dissolution rate of28days were less than75%, which conformed to the industry standards of slow/controlled-release fertilizer specified in CEN. The cumulative dissolution rate of coated fertilizer A and B were lower than the uncoated fertilizers, and the dissolution rate of coated fertilizer A and B were more uniform, the release trends were the gentle parabola or the trend in recent slash. Under the premise of reducing the waste of fertilizer resources, the supply nutrients of fertilizer were consistent with the demand for nutrients during the crop growth, suited for field crops growing shorter. Comparing the initial dissolution rate and cumulative release curves of coated and uncoated fertilizer A and B, when the compound coating agent for controlled-release fertilizer coated fertilizer A, the initial dissolution rate of nutrients N, P, K were smaller, the release trend were more gently, the dissolution rate were more uniform, controlled-release effects were better when the compound coating agent for controlled-release fertilizer KSFBJ coated with low nutrient content of ordinary fertilizer. Through comparing the nutrient cumulative release curves of the coated fertilizer prepared by the compound coating agent for controlled-release fertilizer KSFBJ and the coated fertilizer prepared by the single coating agent for controlled-release fertilizer KSFJ, the controlled-release properties of the compound coating agent for controlled-release fertilizer was better than the single coating agent for controlled-release fertilizer.3. The physico-chemical properties of compound coating agent for controlled-release fertilizer KSFBJ results indicated that, the pH of the compound coating agent for controlled-release fertilizer was5.80, slightly acidic, and conducive to the growth of crops; viscosity was25.5mPa-s, moderate viscosity could achieve uniform coating effect, and easy adhesion between fertilizers; film was uniform, coating film could scraped completely and was water-insoluble, film-forming was good; the short forming time which only need5minutes illustrated the coating film on the fertilizer surface fast curing and the coated fertilizers easy to dry; the coating uniformity could up to95%, indicating that the coating agent was evenly attached to the fertilizer surface, and the coating film was better, at the same time, the coating expulsion rate was less than2%, indicating that the coating film could be firmly attached to the fertilizer surface, not falling; the hygroscopic property of the coated fertilizer was less than the uncoated fertilizer, indicating that the controlled-release fertilizer was not easy to absorb moisture; the storage properties were good so that the compound coating agent for controlled-release fertilizer was easy to storage and transport; The physico-chemical properties and storage properties of compound coating agent for controlled-release fertilizer KSFBJ were better than the single coating agent for controlled-release fertilizer.