Location

Askov Experimental Station

Starting year

The long-term C3- to C4-conversion experiment was initiated in 1996.

Short description

The C4-crop, silage maize, is the crop grown in the experiment. Its distinctive type of photosynthesis allows for the tracing of changes in the natural abundance of 13C, thereby enabling the fate of carbon-derived residues derived from maize to be elucidated (C4-SOC). In addition, the decay of changes in old C3-SOC can be investigated. Thus, the changes in the otherwise “hidden” SOC pools can be revealed. The experiment stands out as the only C3- to C4-conversion experiment specifically designed to achieve the above objective.

Soil type(s)

Askov: Sandy loam, Inceptisol, Ochrept. 

Lundgaard: Sandy soil, Alfisol, Hapludalf. 

• The experiment comprises three treatments, each of which is replicated three times for each of two soil types: Askov and Lundgaard. Treatment M denotes the incorporation of stubbles and roots only. In treatment M+MB, cylinders receive an additional input of freshly chopped aboveground maize biomass. Treatment M+MF receives maize-derived sheep faeces. One cylinder of each soil type was maintained under C3-crops (C3-treatment). 

Sample archive

The harvest yield from each cylinder is estimated on an annual basis, with a subsample being archived for subsequent analysis. Soil samples are taken every fourth year, air-dried, 2-mm sieved and archived.