Fig. 3. Net cumulative NH₄–N accumulation during anaerobic incubation of (a) soils having N₁ < 75 mg NH₄–N kg^–1 soil, (b) soil having 75 < N₁ < 150 mg NH₄–N kg^–1 soil, and (c) soil having N₁ > 150 mg NH₄–N kg^–1 soil, where N₁ is the total size of the rapidly mineralizable N pool. Curves shown are regression lines based on the two-pool first- and zero-order model using parameters given in Table 5. Soil was sampled from the 0- to 15-cm depth.