Characterization of tropical soil P species and their susceptibility to labile C compounds

Tropical soils are often highly weathered, presenting poor nutritional conditions for plant growth. In these soils, phosphorus (P) is not only depleted, but the remaining P is often not bioavailable as most of the soil P is strongly adsorbed to mineral phases. Under such low accessibility, the productivity of tropical plants is strained, and they need to compete or cooperate with soil microorganisms at the microscale to acquire P from the soil. This acquisition is almost exclusively dependent on the exudation of organic compounds into the soil, that liberate P for the plants. To investigate the effect of different organic compounds on soil P microspatial patterns and speciation, we have conducted a 13C-enrichment microdialysis experiment, which simulates root exudation into the soil. To unravel the correlative relationship between exudates, microorganisms and P we propose the combination of fluorescence microscopy with synchrotron SXM and NanoSIMS.