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v14	v15
37	37
38	38	* '''Ammonium adsorption''' (2). Li et al. (1992) defines FIXNH4 as the proportion of adsorbed NH4+. One may assume that consequently the NH4+ that is not adsorbed is NH4+ x (1-FIXNH4) and that we want to consider this quantity for possible nitrification, transformation to ammonia, .... But in OCN, we do not multiply the state variable (SV) representing NH4+ by (1-FixNH4) but by (1-FixNH4/(1+FixNH4)) (see, [source:branches/orchidee-N/ORCHIDEE/src_stomate/stomate_soilcarbon.f90@19#L746, here]). This tends to assume that FixNH4 represents the ratio adsorped NH4+ to non-adsorped because FixNH4/(1+FixNH4) = (NH4adsorp/NH4non_adsorp)/((NH4non_adsorp+NH4adsorp)/NH4_non_adsorp) = NH4adsorp / NH4tot. This needs to be clarified ...
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	40	* '''Nitrification rate'''. The equation for the nitrification rate comes from Schmid et al., 2001, Nutr. Cycl. Agro (eq.1) but the environmental factors used are from Zhang (2002) who used an other equation, especially for Temperature effect on nitrification. I don't know how this can be mixed together ? This seems particularly inappropriate because the default fraction of N-NH4 which is converted to N-NO3 appears equal to 2 day-1 (a factor "2" in the equation, see [source:branches/orchidee-N/ORCHIDEE/src_stomate/stomate_soilcarbon.f90@19#L805,here]). In Schmid et al., the nitrification rate at 20 ◦C and field capacity (knitrif,20) was set to 0.2 d−1 (10 times less...)