Path analysis of phosphorus activation capacity as induced by low-molecular-weight organic acids in a black soil of Northeast China

Abstract

Purpose The present study was designed to assess the potential effects of low-molecular-weight organic acids on the activation of inorganic phosphorus, obtain exact information on the acidity effect of proton and complex effect of organic anion in P availability, and determine the components among phosphorus fractions that contributed the most to inorganic phosphorus activation in black soil. Materials and methods Both oxalic and citric acids treated with different concentrations and pH values were carefully selected. The activating amounts of total inorganic phosphorus and individual phosphorus fractions were estimated. Path analysis was used to analyze the direct and indirect effects on inorganic phosphorus activation. Results and discussion The amount of total activating-P i increased as the concentrations of oxalic and citric acids increased. When the concentrations were ≤ 1.0 mmol L −1 , oxalic acid exhibited a lower capability than citric acid in total activating-P i , but when the concentrations were ≥ 1.5 mmol L −1 , oxalic acid exhibited a higher capability. The amount of total activating-P i decreased as pH of LMWOAs increased. LMWOAs-induced P i activation might be attributed to combine acidity and complex effects. Conclusions Correlation analysis showed that the activation of total P i was significantly correlated with the activation of H 2 O-P i , NaHCO 3-P i , NaOH-P i , and HCl-P i (p < 0.05). Path analysis revealed that soil activating-H 2 O-P i mainly affected P i activation through an indirect path. The contribution of activating-NaHCO 3-P i alone was maximal on the total activating-P i by both the direct and indirect effects, followed by activating-NaOH-P i and activating-HCl-P i .

The role of low molecular weight organic acids in the release of phosphorus from sewage sludge-based biochar

“…Similarly, an inverse relationship between the amounts of P released from soils and the pKa values of the organic acids was reported by Harrold and Tabatabai (2006). The importance of the extractant concentrations was also highlighted by Yang et al (2019a), where when the concentrations were ≤ 1 mM, oxalic acid lower proportion of P than citric acid, and when the concentrations were ≥ 1.5 mM, oxalic acid was more effective. Thus, the similar pattern was expected also in this study, if 1 mM concentration of the acids was used.…”

Effect of Freeze–Thaw Cycles on Phosphorus Fractions and Their Availability in Biochar-Amended Mollisols of Northeast China (Laboratory Experiment)

“…Indirect effects of P fractions on the P a occurred from the product of the simple correlation coefficient between soil P fractions and the path coefficient. The correlation between P a and individual P fractions was the sum of the entire path connecting two variables [39]. All statistical analyses were performed with SPSS 22.0 (IBM Institute, Armonk, NC, USA) with a significance threshold of p < 0.05.…”

Organic acids promote phosphorus release from Mollisols with different organic matter contents

“…The total inorganic P (TP i ) concentration in the supernatant was determined using the molybdenum blue colorimetric method (Murphy & Riley 1962). The amount of TP i release was defined as the difference between the amount of TP i extracted with and without the organic acids in the extractant solution (Yang et al 2019a). Each soil sample that had been extracted with an organic acid was then washed with alcohol to remove the residual organic acid between the soil particles (Liu et al 2009), then the P i fractions were determined using the sequential extraction method modified by Hedley et al (1982).…”

“…P is present in the soil in various forms that have a different availability and solubil-ity. A sequential P fractionation scheme based on a method developed by Hedley et al (1982) has been used in many studies of soil P fractions (Rakotoson et al 2015;Yan et al 2017;Yang et al 2019a). This method allows one to determine the P availability in soils associated with vegetation (DeBruler et al 2019;Liao et al 2020), management regimes (Shi et al 2015), and land use change (Sun et al 2019).…”

“…Organic acids exuded by plants and soil microbiota (Romanyà et al 2017) can transform insoluble P into plant-available forms and, therefore, affect the P bioavailability (Wang et al 2018;Yang et al 2019a). However, the abilities of organic acids to solubilise P are dependent on the soil type, the soil organic matter (SOM) content, and the structures and concentrations of the organic acids themselves (Oral & Uygur 2018).…”