Organic acid concentration thresholds to mobilize phosphorus (P) in dryland soils
Year: 2025
Type: article
Abstract: Available phosphorus (P) concentrations are low in dryland soils due to high pH values linked to the presence of pedogenic carbonates. Thus, dissolution and mobilization of P compounds are important controls on P availability for plants, microbes, and biocrusts. One process that has been hypothesized as a way for dryland organisms to acquire P is the exudation of organic acids that can release bound P compounds. To explore this process, we assayed the critical thresholds of organic acid (citrate, malate, and oxalate) concentrations required to mobilize P in a range of dryland soils. Our results showed that: (1) Concentrations of oxalate or citrate, on the order of 1000 µmol/L are needed to effectively mobilize PO 4 3− in all landforms and microsites we examined. (2) The in situ organic acid concentrations in bulk soil core samples were < 100 µmol/L, both under plant canopies and in interspaces, suggesting they are below the needed threshold to mobilize P. However, hot spots such as the rhizosphere, though difficult to quantify, may still be locations where the concentration of organic acids approach the threshold. (3) Oxalate was the most effective in releasing PO 4 3− , likely as a result of removing aqueous Ca via calcium oxalate precipitation. Overall, our results show that for P acquisition through organic acid production to be effective in dryland soils, a relatively high threshold of organic acid concentration that substantially exceeds bulk soil concentrations must be reached, suggesting that if it occurs, it is restricted to localized microsites within the soil matrix.
Source: Biogeochemistry
Institution: The University of Texas at El Paso
Language: English
Subfield: Waste Management and Disposal
Field: Environmental Science
Domain: Physical Sciences
SDG: Life on land
Open Access status: hybrid
Estimated APC paid: $3,390
Awards: MRI: Acquisition of inductively coupled plasma-optical emission spectrometer for research and education uses in water, energy, and environmental sciences, G4886678888, Network Cluster: Patterns and controls of ecohydrology, CO2 fluxes, and nutrient availability in pedogenic carbonate-dominated dryland critical zones
OpenAlex ID: W4417526374