Biochars derived from crop straws increased the availability of applied phosphorus fertilizer for maize in Ultisol and Oxisol

Baquy, M Abdulaha-Al; Jiang, Jun; Xu, Renkou

Biochars derived from crop straws increased the availability of applied phosphorus fertilizer for maize in Ultisol and Oxisol

2020

Baquy, M Abdulaha-Al | Jiang, Jun | Xu, Renkou

The extensive use of phosphorus (P) fertilizer is a common practice due to the suboptimal P in variable charge soils for better crop growth. The aim of this study was to increase our understandings and disclose the mechanisms for increase in P availability in Ultisol and Oxisol by biochars derived from crop straws. Incubation and greenhouse pot experiments were conducted to attain the objective. Results from incubation study indicated that biochars derived from different crop straws increased P recovery in both Ultisol and Oxisol. Biochars increased the repulsion of soil surface to phosphate (PO₄³⁻) anions due to increased soil CEC, and thus increased P recovery; acidic functional groups on biochars competed for soil sorption sites with PO₄³⁻, and thus increased P recovery. While the formation of insoluble PO₄³⁻ with divalent cations of calcium (Ca) and magnesium (Mg) from the biochars reduced P recovery. P recovery was increased with increasing soil pH and biochar application rate for each biochar type. The lower content of Ca²⁺ and Mg²⁺ in rice straw biochar led to greater increase in P recovery than canola and peanut straw biochars. When two soils were compared with each other, P recovery was higher in Ultisol than Oxisol due to the presence of large amount of Fe and Al oxides in Oxisol. Results from pot experiment showed that plant dry matter yield and P recovery by maize were increased with increasing rate of rice straw biochar applied over control. Therefore, application of P fertilizer in rice straw biochar–amended soils will increase P availability to crops and thus crop yields in variable charge soils.

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