Recognizing biochar from the angle of soil humus

It is not clear in the components, structure and function of soil organic matter for its extraordinary complexity. Both the terra preta soil in Amazon region developed by the cultivation of ancient Indians for thousands of years. The results in biochar soil amendment during recent two decades show that biochar may be one of the most important matrix for a fertile soil. Biochar can be considered as pyrogenic particulate humus-like matter since it has many similarities with soil humic matter known as the most important component of soil organic matter, in both features of structure and function. Most of the amended biochar become the free particulate organic matter, while a small portion may into heavy fraction of soil organic matter through either directly combining with clay minerals or transforming into humic materials. It may be a highly feasible approach to low C or even negative C agriculture if plant biomass is converted into biochar and then used as soil amendment. The scientific questions furtherly answered may include as followings. 1) How can we permanently establish the desirable soil root zone through biochar amendment in order to meet crop root development? (2) How does biochar interact with soil clay minerals? (3) How does biochar interact with soil humic materials? (4) How does biochar drive soil microbial C pump? (5) How does biochar intermediate organic matter mineralization?