Development of a carbon-based slow release fertilizer treated by bio-oil coating and study on its feedback effect on farmland application

Biochar materials have been widely used as an adsorbent or carrier material to produce carbon-based slow-release fertilizers. The traditional biochar-based fertilizers have a limited release effect, so it needs to be further strengthened. The impact of initial biochar preparation conditions on quality of the final carbon-based fertilizer products is also unclear. Therefore, in this study, three different anaerobic preparation atmospheres-N-2, CO2, and H2O(g) were used to prepare three different biochar raw materials at 400 degrees C, then we analyzed and compared their initial nutrient content as well as physical properties like porosity, surface chemical functional group, the results turned out to be that, the biochar prepared under the atmosphere of CO2 and H2O(g) is more suitable as a raw material for the production of carbon-based slow-release fertilizer. At the same time, bio-oil coating treatment of biochar having been loaded with N, P and K nutrients was carried out, and a new biochar-based slow-release fertilizer was developed. By analyzing and comparing the sustained-release ability before and after the coating, we found that the oil-coating treatment could decrease the nutrients dissolve rate in water by about 15%, while the leaching rate in soil decreased by 3-5 percentage points, it has firmly proved the film-forming properties of the bio-oil and its coating treatment to strengthen the slow release capacity. The pot experiment was divided into blank (CK), ordinary fertilizer treatment group (F), uncoated carbon-based fertilizer treatment group under 3 atm (BN0, BC0, BH0), and coated carbon-based fertilizer treatment under 3 atm (BN1, BC1, BH1). The results showed that the growth of plants in F and CK treatment groups was significantly inhibited, while the other treatment groups had little difference, indicating that the short-term effect of slow-release fertilizer developed in this study on crop growth is not obvious, but it still has a large promotion potential for a long period of time. (C) 2019 Elsevier Ltd. All rights reserved.