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+========================================
+
+h1. N2O emission from nitrification
+
+"Parton et al. 1996":http://onlinelibrary.wiley.com/doi/10.1029/96GB01455/abstract gives function
+
+$N_{N2O} = N_{H2O} \cdot N_{pH} \cdot N_T \cdot (Kmx + Nmx \cdot N_{NH4})$
+
+with
+$N_{N2O} = ((WFPS-b)/(a-b))^{d\cdot (b-a)/(a-c)} \cdot ((WFPS-c)/(a-c))^d$
+* $WFPS$ is water filled pore space of the soil
+* parameters $a$ to $d$ given for sandy and medium soil
+* source for functions given as Doran et al. 1988
+
+$N_{pH} = 0.56+1/\pi\cdot \arctan(\pi\cdot 0.45 \cdot(pH-5))$
+* we ignore this limitation
+
+$N_T = -0.06+0.13\cdot \exp(0.07 \cdot T_{soil})$
+* based on data by Sabey et al. (1959)
+
+$Kmx = 0.00038$ gN m$^{-2}$ d$^{-1}$
+* N turnover coefficient
+* site specific but given for different sites
+* for natural soils given as 3.8 and 3.9 (gN ha$^{-1}$ d$^{-1}$)
+
+$Nmx = 0.003$ gN m$^{-2}$ d$^{-1}$
+* maximum nitrification flux of N$_2$O with excess NH$_4$.
+
+$N_{NH4} = 1 - \exp(-0.0105\cdot NH4)$
+* NH4 here given as $\mu$g N per g soil
+* in the same range as gN m$^{-2}$ so that formula taken as it is
+
+Process is incorporated in source:branches/nitrogen_rev2142/src/soil/littersom.c after mineralization.
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