Dr Markus Steffens1, Marius Mayer1, Dr. Andreas Fliessbach1, Dr. Paul Mäder1
1Research Institute of Organic Agriculture FiBL, Frick, Switzerland
Soils contain more carbon (C) in the form of organic matter (soil organic matter = SOM) than the entire atmosphere and global vegetation put together. They are thus a central component of the global C cycle and its largest dynamic reservoir. On the one hand, intelligent agricultural practices are discussed as a way of mitigating climate change because they can increase the amount of SOM and thus actively remove C from the atmosphere. On the other hand, all intensively used soils lose C in the long term. Central questions in this context revolve around the extent and dynamics of storage, the stabilisation mechanisms involved and the impact of agricultural use on the C budget.
The DOK experiment is an agronomic long-term experiment near Basel (Switzerland), which has been comparing biodynamic, organic and conventional management systems for 40 years (six crop rotation cycles) and has an extensive soil sample archive covering the entire period. Within the “DynaCarb” project, we are investigating how density and particle size fractions of SOM change qualitatively and quantitatively during the 40-year test period. We compare four different fertilization systems (each with four replicated plots): an unfertilized control, pure mineral fertilizer, pure organic fertilizer, and a combined mineral-organic system in the years 1982, 1989, 1996, 2003, 2010, and 2017. Using physical fractionation (density and particle sizes) and CN analyses, SOM is separated into particulate and mineral-associated fractions and their development is quantitatively investigated during six crop rotation cycles. We use solid-state 13C NMR spectroscopy, N2 gas adsorption and radiocarbon dating to estimate the C sequestration potential of soils, their saturation and the dynamics of C storage.
“DynaCarb” investigates the medium- and long-term effects of different agricultural systems on SOM. These results are of great importance for the evaluation of the C-sequestration potentials of agricultural soils and for the identification of suitable utilization and fertilization strategies.
Markus Steffens is theme leader for climate and agriculture at the Research Institute of Organic Agriculture FiBL in Switzerland. He received his Ph.D. in soil sciences from the Technische Universität München and did his diploma in applied environmental sciences at Trier University, Germany. Markus’ work is focused on soil organic matter and soil quality in agricultural systems and the application of (imaging) spectroscopic techniques to elucidate the underlying processes.