Fig. 2. Cumulative leaching of Ca (left panel) and Al (right panel) calculated from the leachates collected at the bottom of the columns. Values are means of three replicates ± standard deviation. N, no Ca added; G, gypsum; L, CaCO₃; LG, CaCO₃ + gypsum; c₀, no compost; c_m, 34.4 g kg^-1 compost; c_h, 68.8 g kg^-1 compost.