Abstract
Biochar is a black, C-rich, stable, solid product from pyrolysis of biomass materials. Although it was known as a soil C sequester for a considerable length of time, biochar is also recently advocated in agricultural applications for improving soil quality; therefore, its agronomic value is evaluated. This paper summarizes and discusses the potential of biochar amendment for soil fertility improvement and the effects on crop productivity by reviewing scientific studies performed around the globe. Researches have shown that biochar amendment significantly enhances the nutrient availability and nutrient retention of a wide range of soils. The soil fertility amelioration is achieved through improving soil physical, chemical, and biological properties. The capacity of a biochar to provide or enhance soil available nutrients, however, is determined by the feedstock and production conditions of the biochar. Biochars produced from nutrient-rich feedstocks contain comparatively high readily available nutrients. In general, biochar amendment improves soil fertility, yet the effect is more apparent for poor (e.g., acidic, highly leached) soils than for originally fertile soils. The impacts of biochar amendment on crop growth are largely positive, with mixed results dependent on the biochar quality, application rate, soil type, and crop species. Further research is needed to fully uncover the role of biochar in enhancing soil fertility and crop growth.