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Department of Geography Soil Science and Biogeochemistry

P availability and turnover of the organic belowground inputs into a Ferralsol (Affiliated project)

Tropical grasslands cover approximately 1500 Mha that corresponds to 44% of the worldwide grassland area and are mainly growing on Oxisols and Ultisols. These highly weathered soils usually have low plant available phosphorus (P) contents due to the strong P sorption onto the soil solid phase.  To cope with P limitation, plants develop specific strategies for acquiring P such as root system extension or root exudation enhancement, which influence plant belowground inputs. However, a quantitative understanding of combined root and rhizodeposition C and N inputs in response to P availability has not yet been studied.
Objectives and approach:

Understand the role of P availability on the regulation and the turnover of belowground organic matter inputs (roots and rhizodeposition) from plants in highly weathered tropical soils. Along a gradient of plant available P, we will quantify and characterize belowground C, N and P input by functionally distinct tropical plant species (grass and legume) using a 13C, 15N, 33P labelling approach applied under controlled conditions of the greenhouse. Then, we will be able to follow the incorporation of plant-derived C, N and P into soil nutrient pools over time.


Figure 1: Site in Madagascar

Astrid Oberson (ETH Zurich), Emmanuel Frossard (ETH Zurich), Samuel Abiven (Soil Science and Biogeography Unit, Department of Geography, University of Zurich)
Idupulapati M. Rao (International Center for Tropical Agriculture (CIAT), Cali, Colombia)
Funding source:
The project is funded by the Swiss National Science Foundation (SNSF)

Weiterführende Informationen

Persons involved


Astrid Oberson (ETH)



Samuel Abiven (UZH)

Emmanuel Frossard (ETH)


PhD Candidate

Pierre Stevenel