Rhizodeposition is the main source of carbon and energy for nutrient mobilization in subsoil (RhizoCNP)

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Rhizodeposition is a very important source of carbon (C) and energy for microorganisms mobilizing nutrients in soil, but no data is available regarding the importance of rhizodeposition in subsoil. This project aims on the estimation of C input into subsoil, tracing the root-derived C in biopores formed by roots and earthworms, calculation of the budget of root-derived C and its contribution to nutrient mobilization in subsoil. Plants with different root systems (chicory and alfalfa) will be labeled in field by 13CO2 and under controlled conditions by 13C and 14C. Subsequently, the C budget will be followed by both isotopes including incorporation into microbial molecular markers (13C-PLFA) and biopore coatings. Rhizosphere extension in the subsoil will be estimated by analyzing distribution profiles of root-derived C (14C) and depletion of N (15N), P (33P), and K, depending on distance to root and along individual roots (by 14C phosphor-imaging). Availability of nutrients (N, P) in subsoil and biopores and nutrient mobilization by root exudates will be tested in batch experiments. An approach to evaluate the origin of individual biopores will be developed based on composition of lipid biomarkers. The subproject will deliver parameters for modeling of C flow within and into the subsoil, rhizosphere extension, diffusion profiles of nutrients and root exudates, and nutrient availability depending on distance to roots.