Soil Denitrification Potential (WMS Service)

The denitrification potential describes the ability of the soil through microbial conversions and under anaerobic conditions to convert part of the nitrate back into air nitrogen (e.g. nitrous oxide). Prerequisites for nitrate degradation are the presence of nitrate, the absence of oxygen and the presence of oxidable organic matter. The denitrification potential is derived on the basis of the low axis-wide soil overview map (BÜK50) and is valid up to a depth of two meters. Each soil type is assigned a denitrification stage with an average annual rate depending on the influence of groundwater or reservoir water. In total, there are five denitrification stages, which are characterised by mean denitrification rates of 5, 20, 40, 60 and 100 kg N/ha*a (in peat-containing substrates at a high groundwater level 150 kg N/ha*a). The lowest denitrification rates have low humous sites where water saturation of the soil body is excluded all year round. The denitrification potential of soils increases with an increase in humus content or due to the occurrence of temporary wetness during the influence of groundwater or reservoir water. The second denitrification stage represents an average denitrification rate of 20 kg N/ha*a. In principle, the highest denitrification rates can be expected as soon as groundwater is present in humus- or sulfur-containing soil layers. At denitrification level 5 (>> 150 kg N/ha*a), the denitrification rate can be up to 3 000 kg N/ha*a. According to WELL et al. (1999, 2005) such rates are mainly found in low bogs and humus-rich soils, where the groundwater surface is in the peat body at = 6 dm and GOK all year round. As organic matter is mined in water-saturated soil layers during denitrification, it can be assumed, especially for mineral horizons, that the denitrification rate decreases over the decades and centuries. Groundwater reductions can also significantly reduce the denitrification performance in the soil zone of a site (WienHaus et al., 2008).