Evolution of biochar properties in soil

As discussed in other chapters of this book, pyrogenic carbonaceous materials (PCM) deposited in soil from natural or deliberate wildfi res and engineered biochar products intentionally added to soil are known to have signifi cant effects on soil biogeochemical processes and in many cases to infl uence the yield and quality of crops and to enhance the ability of soils to retain chemical contaminants. The physical-chemical properties of raw biochar vary greatly depending on source material and the conditions under which it was formed or made (see Chapters 5-8). Once in contact with soil, however, biochar may undergo changes in physical-chemical properties over time. Any consideration of the behaviour and effects in soil of biochars must take into account these changes. The aim of this chapter is to discuss what is known about such changes.