Preparation And Properties Research Of Biochar Coated Controlled-release Urea

Nitrogen fertilizer made great contributions to the Chinese food security. In the past decades,the overdose of nitrogen fertilizer with low utilization results in a waste of resources and environmental pollution. Macro molecular polymers coated urea could significantly increase the utilization of nitrogen, minimize or avoid the impact of low utilization of nitrogen. However, most of coated materials are very expensive and highly dependent on petroleum. In addition, parts of the coated materials are hard to be decomposed in the soil, which would cause secondary pollution of the environment.In this paper, we firstly propose a low-cost method of producing coated materials that mainly consists of modified vegetable oils and con straw biochar. The materials can be decomposed and increases the utilization of nitrogen by absorbing the nitrogen in the soil. Secondly, based on this material, we produce 11 kinds of biochar coated controlled-release urea. We also study the nutrient release characteristics of fertilizers as well as the desorption and degradable performances of coated materials. The main results are in the following:1. Useing three kinds of waste vegetable oil as the main raw material to preparate three kinds of coated adhesive,and Filtering through curing test. The results showed that the best of curing time and curing product characters is binderAb, binderBb is difficult to curing. The products of binderCb curing is presented of solid-liquid mixed state. So binderBb and binderCb are not preparation of biochar coated controlled-release urea.2. Using binderAb and biochar as the main coated materials to prepare 11 kinds of controlled-release biochar coated urea by one-step method and two-step method respectively. And filtered coated process conditions: Optimum coating temperature at about 60?; One time spray amount of binder Ab at 6 g; One-step method needs 23 sprays and two-step method needs 30 sprays.3. Using static water dissolution rate test to study the nutrient release characteristics of 11 kinds of biocher coated controlled-release urea. The results showed that Exploiting the period of biochar coated controlled-release urea by one-step method is longer Generally than by two-step method. Exploiting the period of SPSU0 is as long as 62 days. Exploiting the period of biochar coated controlled-release urea by two-step method is shorter, Exploiting the period of DPSU4 is only 17 days, Which is the longest.4. Studying the soil NH4+ adsorption?Soil degradation characteristics?Scanning electron microscopy and Infrared characterization of coated materials. The results show that:(1)Coated wrecks has significant adsorption on NH4+, Adsorption quantity is increased with the increase of Coated wrecks content in soil.(2)Coated material has certain degradability in the soil, and shows a negative correlation with biochar content, C0 degradation of coating materials that is not including biochar in the best, average amount of degradation is 0.07 g monthly; the degradation of coated materials C10 that add 10% biochar is the worst, average amount of degradation is only 0.04 g monthly;(3) By electron microscopic scanning and infrared characterization of visible, the coated wrecks after the water swelling(nutrient release process), part of the biochar and structure of polyurethane disappear, coated layer surface is loose porous state, specific surface area increased, It is benefit on NH4+ adsorption.5. Using the corn pot experiment to study the fertilizer effect, the results showed that fertilizer can significantly increase yield of maize; Used SPSU0 with DPSU4 can obtain the best result, CP7 got better results than CK and CP1, increasing the maize grain yield by 111.7% and 20.3% respectively.