Production And Application Of Slow Release Fertilizer Based On Rice Straw Derived Biochar

Compared with the traditional fertilizer, slow-release fertilizer could effectively reduce soil nitrogen nutrient loss; however, slow-release fertilizers often use the polymer as the coating and the coating materials is easy to cause the destruction of soil structure. Therefore, to find new coated materials to prepare environmental friendly slow-release fertilizer is one of the hotspots in the field. Meanwhile, large amount of rice straw is produced in China where a large amount of rice straw is disposed of through being returned to fields, causing serious green house gas emissions. The biochar created through pyrolysis of rice straw has aromatic stability, which could realize carbon sequestration and has ability of nitrogen retention. Consequently, biochar derived from rice straw has the potential to be used as coating material of slow-release fertilizers. If rice straw is carbonized to produce solw-release fertilizer, a new way will be provided for the use of rice staw and production of slow-release fertilizer, which will contribute to the control of non-point pollution and green house gas emissions in agriculture. In this paper, the study of a prolysisi system for rice straw derived biochar production was conducted to produce biochar as the coating materials. Then based on the orthogonal experimental design different kinds slow-release fertilizer was prepared to find suitable fertilizer for rice cultivation. Upon this, pot and field experiment was carried out to investigate the effects of the chosen fertilizer on control of non-point pollution and on the yield of rice. The main results are as follows:(1) Through the operation of the prolysisi system, the effects of air put and residence time on yiled and quality of biochar derived from rice straw were investigated.2600m3/h for air put and1h for residence time were chosen to produce biochar for further experiment in the practical deployment. Under the selected condition, yield of the prolysis system could reach34.9%, while carbonization temperature was between400-500℃and the biochar contained53.67%carbon content.(2) Biochar derived from rice staw and common compound fertilizer was chosen to make biochar-coated fertilizer. An orthogonal experimental design method was applied to investigate how the blending ratio of biochar/coal humic acid/bentonite and adhesive type influenced N release from the coated granules. The optimum coating combination for coated granules was25%biochar,4%bentonite,10%coal humic acid and modified corn starch as the adhesive. The best-prepared coated fertilizer could meet the requirement of the newest Chinese standard of nutrient release measurement from slow release fertilizer (GB/T23348-2009). It was found that biochar played a highly effective role in slowing N release compared to the other compounds tested. The formation of a compact layer by the interaction of the compounds may mainly contribute the slow-release ability of biochar-coated fertilizer.(3) With biochar and selected fertlizers, pot and field experiment was carried out to investigate the effects of biochar and chosen fertilizers on control of non-point pollution and the yield of rice. The results of artificial rainfall experiment showed that under the condition of the same rainfall, total nitrogen runoff with slow-release fertilizer was reduced by27.3%-56.6%compared with CK. The expressions about TN concentration and time in the field experiment were got by multinomial fit and it told the coefficient of CK is higher than SRFA. This showed that the SRFA application can reduce risk of N runoff loss while increase the rice yield by7.7%.