Fig. 1. Total organic matter (OM) in control and amended topsoils (0–30 cm) measured before (12 Mar. 1999), 2 d after (24 Mar. 1999), 6 mo after (28 Sept. 1999), and 18 mo after (26 Oct. 2000) the amendment (mean and standard error of n = 3). For each sampling date, columns with the same letter are not statistically different (Tukey's Honest Significant Difference test, p < 0.05).