The model experiment (anaerobiosis) determined the ammonium ion concentration in soil solutions, Eh, and pH in soil sediments using soil samples fully saturated with water with incubation occurring at 5, 10 and 20°C during the periods from 0 to 60 days. A total of twelve samples from loess soils representing surface-humus horizons were taken from various parts of 4 eroded slopes of a small river (the Ciemięgacatchment near Lublin, SE Poland). Differentiation in ammonium ion concentrations in the range of 0.54–4.48 mg dm⁻³ was found, depending on the sampling location in the catchment area and slope, as well as on the duration of soil sample incubation time.