Enhanced the plant germination in sandy soil by novel sludge-based biochar prepared with residual sludge after EPS extraction as soil amendment

Abstract

The preparation of novel sludge-based biochar and its application as soil amendments are considered as an environmentally friendly way to realize sludge recycling. In this study, a novel sludge-based biochar (RBC) was prepared by residual sludge after extracellular polymers (EPS) extraction, and the effect of RBC as soil amendment on the ryegrass germination in sandy soil was explored. The results indicated that the biochar yield by residual sludge after EPS extraction was higher than that by raw sludge. Compared with the raw sludge-based biochar (SBC), a variety of new functional groups and crystalline structures were formed in RBC, and the specific surface area and pore volume were significantly increased. Furthermore, a largest NH₄⁺-N adsorption capacity of 7.6 mg/g was achieved by HNO₃ modified RBC (MRBC) under an optimum pH of 7. Moreover, the ryegrass germination rate and ryegrass height were increased by 52.0 % and 213.4 % in sandy soil with MRBC adsorbed with NH₄⁺-N as soil amendment compared with that in sandy soil with SBC addition. Accordingly, RBC has great potential for the preparation of novel sludge-based biochar and plays a prominent role as a soil amendment in enhancing plant growth in sandy soil. The above research will provide a new direction for the advanced resource utilization of sewage sludge.