Oxalate metabolization by soil microorganisms was assessed using a calcium oxalate clearing medium and14CO2 release from [14C]-oxalate. Three saprophytic fungi, two bacteria, and one actinomycete tested produced14CO2 when grown in culture with [14C]-oxalate, yet failed to test positive for oxalate degradation using a calcium-clearing medium. A field plot was then established to determine the effects of oxalate inputs on oxalate metabolism. The amount of [14C]-oxalate metabolized by soil microorganisms and the number of bacteria metabolizing oxalate increased within 24 h after the addition of oxalic acid at a concentration of 11.1 μmol g-1 soil. Oxalate metabolism and bacterial numbers returned to the baseline within 84 days. Soil phosphate concentrations increased significantly above baseline 7 days after the addition of oxalate and did not return to prespike levels. Fungi, bacteria, and actinomycetes were able to metabolize oxalate. Therefore, while oxalate can influence P cycles by increasing the amount of available phosphates, that increase is mediated by microbes that metabolize the oxalates.