Fig. 1. Cumulative dissolved organic carbon (DOC) leaching, 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 added (values for N, G, L, LG all fell on this line); c_m, 34.4 g kg^-1 compost; c_h, 68.8 g kg^-1 compost.