Effect of biochar incorporation on phosphorus supplementation and availability in soil: a review

Purpose Phosphorus (P) retrieval from crop residues has attracted significant attention in sustainable management of P resources. Biochar has the potential to enhance soil P availability and enlarge P pools. However, only few reviews have been reported on the factors and mechanisms of the effect of biochar on replenishing soil P and improving P availability. Materials and methods The current studies on biochar effects on improving soil P level, as well as the underlying factors and mechanisms were reviewed. Results and discussion Biomass (especially livestock manure and municipal sewage) derived biochar contains abundant nutrients and, hence, can directly increase soil available P levels. Most of the amended biochar could change soil physical and chemical properties, such as soil porous structure, pH, cation exchange capacity, and adsorption potential toward P. These variations are associated with P forms and availability in soil matrix. Moreover, soil biota and phosphatase, which increased in the presence of biochar, could solubilize insoluble inorganic P and mineralize organic P, thus enhancing P availability. However, the efficiency of biochar is governed by the properties of biochar and amended soil, and cultivation strategies. Conclusions Studies illustrating the available P sources in biochar-amended soil, quantifying the contribution of biochar-amended soil microorganisms in improving P level, enhancing the slow-release potential of biochar formulations, and inspecting the effects against comprehensive long-term field analyses are considered to expand our knowledge on the effect of biochar amendment on P supplementation and availability in soil.