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Phosphorus release kinetics and solubility capacity of phosphorus fractionation induced by organic acids from a black soil in northeast China

Yang, Xiaoyan, Chen, Xiangwei, Yang, Xitian
Canadian journal of soil science 2019 v.99 no.1 pp. 92-99
citric acid, equations, fractionation, inorganic phosphorus, oxalic acid, path analysis, phosphorus fertilizers, soil, solubility, solubilization, China
Phosphorus (P) fertilizers are added to improve the soil P fertility, but the rate of P release can greatly influence its availability. Organic acids are effective in the release of inorganic P (Pᵢ), but the contribution of each Pᵢ fraction is not well understood. This study reported the transformation rate of P and solubility of Pᵢ fractions induced by organic acids. Path analysis was utilized to explore the direct and indirect effects of Pᵢ fractions on the amount of total Pᵢ (TPᵢ) solubilized. Results showed that the P release was initially rapid, followed by a slower release that lasted up to 2160 h, and the Elovich equation was the best-fitted kinetic equation to estimate the transformation rate of available P. The amount of TPᵢ-solubilized by oxalic and citric acids tended to increase with increasing organic acid concentrations. Oxalic acid exhibited a lower TPᵢ-solubility capability than citric acid when the organic acid concentration was ≤1 mmol L⁻¹, whereas citric acid was higher at ≥1.5 mmol L⁻¹. The Al-P-solubilized had the highest content of studied fractions, and path analysis revealed that the Al-P-solubilized exhibited a significant direct effect on TPᵢ-solubilized. Thus, Al-P is a potential P source in black soil.