Different mechanisms of organic and inorganic phosphorus release from Mollisols induced by low molecular weight organic acids

Abstract

Enhancement of inorganic phosphorus (Pi) release by low molecular weight organic acids (LMWOA) increases soil phosphorus (P) availability to plant, but the release of organic phosphorus (Po) and the associated kinetics of both Pi and Po release by LMWOA have not been well considered. The aim of this study was therefore to investigate the impacts of three common LMWOA (citric acid, oxalic acid and malic acid) on the kinetic release of Pi and Po in a black clay soil in Northeast China. All kinetic data were well described by Elovich and power functions models (P <0.01). LMWOA at 10 mmol kg-1 soil increased the rate of the kinetic release of both Pi and Po. Po released by LMWOA derived from the soil labile Po (NaHCO 3-Po) fraction in the order of oxalic acid (3.58 mg kg-1) > citric acid (2.67 mg kg-1) > malic acid (1.76 mg kg-1). In contrast, Pi release by LMWOA resulted from mobilization of the moderately labile NaOH-Pi (Fe/Al-P) and HCl-Pi (Ca-Pi) fractions in the order of citric acid (4.83 mg kg-1) > oxalic acid (2.40 mg kg-1) > malic acid (2.04 mg kg-1). Therefore, the release of Po by LMWOA is mainly via the dissolution of soil labile Po (NaHCO 3-Po) rather than via chelation of organic acid ligands.

Organic acid regulation of inorganic phosphorus release from Mollisols with different organic matter contents

“…Knowledge of the chemical transformations of phosphoruscontaining compounds is crucial for the maintenance of soil P levels by supplementation. It has been widely speculated that organic acids exuded by plants and soil microbiota (Romanyà et al 2017) may enhance the mobilization of soil inorganic phosphorus (P i ) to influence phosphorus availability (Liu et al 2017;Wang et al ,2016Wang et al , , 2018. As chelating agents, organic acids can displace phosphorus from Fe/Al-P and/or Ca-P compounds in soils, which changes the proportions of iron/aluminium-bound phosphorus and calcium-bound phosphorus (Hinsinger, 2001;Wang et al 2015).…”

Soil phosphorus fractions in an apple orchard with different weed managements

“…The higher PiHCl contents found in HR can be due to the weed management used, since the cut of plant species causes physical stress, making the plants to increase their photosynthetic rates and synthesis of phytohormones, such as gibberellin (Hebert et al, 2019;Liu et al, 2019). In addition, the root exudation of organic acids, such as citric, malic, and oxalic acids, increases as a strategy to dissolve compounds that have P in their constitution, making P accessible and increasing its contents in the soil solution (Mora-macías et al 2017;Wang et al, 2017). Research, Society and Development, v. 9, n. 10, e3449108767, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i10.8767 Table 3.…”

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

“…The superiority of oxalic acid compared to other LMWOAs in releasing P from calcareous soils was also reported by Moradi et al (2012). The release of P with the LMWOAs differed for inorganic and organic forms of P, where the extractability of organic P followed the order oxalic acid > citric acid > malic acid, whereas the release of inorganic P followed the order citric acid > oxalic acid > malic acid (Wang et al 2018). These findings indicate the importance of the P speciation in the soil/biochar, as well as the physicochemical parameters of the soil, and the fate of P having contact with LMWOAs.…”

“…Many previous studies have documented the role of organic acids in P solubilization in the soil. Generally, an acidic environment can significantly enhance the solubility of P minerals (Chen et al 2006;Li et al 2016;Wang et al 2018). Soil organic acids (OAs) can be broadly classified into two groups, namely high molecular weight OAs (HMWOAs) and low molecular weight OAs (LMWOAs).…”