Nitrification and Denitrification
The turn-over processes of ammonium to nitrate (nitrification) and of nitrate to dinitrogen (denitrification) are described as:
\(N\) Nitrification rate \([kg \, N \, m^{-3} \, d^{-1}]\)
\(K_{NO}\) Nitrification rate coefficient at standard conditions \([d^{-1}]\)
\(c_{NH_4^+}\) \(NH_4^+\) concentration in soil \([kg \, N \, m^{-3}]\)
\(f_N(T)\) Reduction factor temperature (Fig. 2)
\(f_N(\theta)\) Reduction factor soil moisture (Fig. 3)
Figure 1: \(f_N(\theta)\) – Reduction factor for nitrification in dependence of the soil water potential (Abrahamsen and Hansen, 2000).
Figure 2: Reduction factor for nitrification (\(f_N(T)\)) and denitrification (\(f_D(T)\)) in dependence of soil temperature (Abrahamsen and Hansen, 2000).
\(D_{pot}\) Potential denitrification rate \([kg \, N \, m^{-3} \, d^{-1}]\)
\(K_{DO}\) Anaerobic denitrification rate \([kg \, N \, m^{-3} \, d^{-1}]\)
\(\Phi_{CO_2}\) Microbial CO2 release rate \([kg \, C \, d^{-1}]\)
\(f_D(T)\) Reduction factor temperature (Fig. 2)
Figure 3: \(f_D(\theta)\) – Reduction factor for denitrification in dependence of water-filled pore space in soil (Abrahamsen and Hansen, 2000).
\(D_{act}\) Actual denitrification rate \([kg \, N \, m^{-3} \, d^{-1}]\)
\(D_{pot}\) Potential denitrification rate \([kg \, N \, m^{-3} \, d^{-1}]\)
\(f_D(\theta)\) Reduction factor soil moisture (Fig. 3) \([d^{-1}]\)
\(V_{NO_3}\) Transport rate \(NO_3^-\) \([kg \, N \, m^{-3}]\)
\(C_{NO_3}\) Soil \(NO_3^-\) concentration
References
- Abrahamsen, P., Hansen, S., 2000. Daisy: an open soil-crop-atmosphere system model. Environ. Mod. Software 15, 313-330.