Biochar affects the distribution of phosphorus in the soil profile by changing the capacity of soil to adsorb phosphorus and its distribution within soil macroaggregates

Abstract A large number of studies suggested that biochar can affect the adsorption of phosphorus (P) in soil and the distribution of P in soil aggregates, but it is still unclear whether biochar can indirectly affect the distribution of P in soil profiles through the influence of these two factors. Therefore, the ability of maize straw biochar to mitigate the risk of loss of P and improve the distribution of P in soil profile was evaluated by studying the capacity of soil to adsorb P from the soil and distribution fractions of it in diverse grain‐sized aggregates of soil. A 5‐year field trial site had received NPK fertilizer inputs at the same rate and one‐time biochar inputs at different rates (0, 15.75, 31.5 and 47.25 t ha −1 ) at the beginning of the experiment. Langmuir and Freundlich equations were fitted to the sorption data of the soil and suggested that the applicataion of biochar can promote P absorption capacity of soil, particularly when the rates of biochar applied were 31.5 and 47.25 t ha −1 . Biochar can improve the stability of soil aggregates, and aggregates with particle sizes of 0.25–2 mm have the highest relative rate of contribution to various fractions of P in the soil. Biochar can promote the accumulation of most of the P fractions in soil aggregates, particularly when the rates of biochar applied were 31.5 and 47.25 t ha −1 . The TP, Ca 2 ‐P, Al‐P, Ca 8 ‐P, moderately labile organic phosphorus (MLOP) and moderately resistant organic phosphorus (MROP) were primarily distributed in the 0–20 cm soil layer. Biochar increased the contents of MLOP and highly resistant organic phosphorus in the soil layer of 0–20 cm while reducing the contents of Al‐P, Fe‐P and occluded phosphorus (O‐P) in the soil layer of 0–20 cm and decreased the contents of TP, Ca 8 ‐P, O‐P and MROP under the 20 cm soil layers. Biochar can change the distribution of P fractions along the soil profile by improving the adsorption of soil P and its distribution in the soil aggregates (0–20 cm).