Kinetics of inorganic and organic phosphorus release influenced by low molecular weight organic acids in calcareous, neutral and acidic soils. Issue 4 (25th June 2015)

• Record Type: Journal Article
• Authors: Wang, Yongzhuang; Chen, Xin; Whalen, Joann K.; Cao, Yanhong; Quan, Zhi; Lu, Caiyan; Shi, Yi
• Is Part Of: Journal of plant nutrition and soil science. Volume 178:Issue 4(2015:Aug.)
• Page Start: 555
• Page End: 566
• Publication Date: 2015-06-25
• Subjects: Plants -- Nutrition -- Periodicals; Soil science -- Periodicals; 630
• DOI: 10.1002/jpln.201500047
• Languages: English
• ISSNs: 1436-8730

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Low molecular weight organic acids exuded by plants roots enhance inorganic P<sub>i</sub> release into soil solution and thereby increases plant‐available Pi in soils. Low molecular weight organic acids may also induce organic P (P<sub>o</sub>) release into soil solution, but kinetics of both Pi and Po displacement from the soil matrix into soil solution of agricultural soils is poorly understood, and the mechanism for P<sub>o</sub> release is not well explained. This study used kinetic experiments to determine the concentrations and release rates of P<sub>i</sub> and P<sub>o</sub> induced by oxalic acid, citric acid, and malic acid in calcareous, neutral and acidic soils. Kinetic data were well described by Elovich (<italic>r</italic><sup>2</sup> = 0.801–0.993, <italic>P</italic> < 0.001) and power functions models (<italic>r</italic><sup>2</sup> = 0.721–0.977, <italic>P</italic> < 0.001). Low molecular weight organic acids at 10 mmol kg<sup>−1</sup> soil induced the exponential release of both P<sub>i</sub> and P<sub>o</sub>, which reached a plateau approx. 480– 2, 880 min after the start of the experiment. Cumulative P<sub>o</sub> release induced by low molecular weight organic acids was ranked as oxalic acid (0.63–3.17 mg kg<sup>−1</sup>) > citric acid (0.61–2.82 mg kg<sup>−1</sup>) > malic acid (0.52–1.76 mg kg<sup>−1</sup>) and mainly resulted from the release of labile P<sub>o</sub> (NaHCO<sub>3</sub>‐P<sub>o</sub>) regardless of soil type. By contrast, oxalic acid was most effective in enhancing P<sub>i</sub> release from the HCl‐P<sub>i</sub> (Ca‐P<sub>i</sub>) fraction of the calcareous soil, and citric acid was most effective in releasing P<sub>i</sub> from the NaOH‐P<sub>i</sub> (Fe/Al‐P<sub>i</sub>) fraction of the neutral and acidic soils. Therefore, the mechanism for the kinetics of P<sub>o</sub> release induced by low molecular weight organic acids is ascribed to their ability to mobilize the labile P<sub>o</sub> (NaHCO<sub>3</sub>‐P<sub>o</sub>) rather than their ability to chelate cations (<italic>i.e.</italic>, Fe<sup>3+</sup>, Al<sup>3+</sup>) bound to P<sub>o</sub> in soil.</p> </abstract>