Fig. 2. Changes in NO₂^– concentrations in Experiments (a) 1, (b) 2, and (c) 3. Experiments 1 and 3 were performed at moisture contents of 40 and 60%, respectively. Nitrite did not occur in Experiments 1 and 3 after Day 6. Error bars are the standard errors of the means (n = 3) in all incubations except in Experiment 3 in the bulk soil where the values are averaged for ¹⁵NO₃^–– and ¹⁵NH₄⁺–labeled treatments (n = 6).