COMPARISON OF WATER, AMMONIUM ACETATE, AND DTPA TO ASSESS THE AVAILABILITY OF MANGANESE IN PEAT SUBSTRATE

An experiment was conducted to assess the suitability of three extract ants, water (press-extract and 1:1.5 volume-extract), 0.5 M ammonium a cetate (NH4OAc) and 0.005 M DTPA for determining plant available manga nese (Mn) in peat substrates. Chrysanthemum morifolium was used as a t est crop. Substrates were selected for differences in Mn-content: moss peat with 0, 15, and 30% Mn-rich clay. The three substrates with each four levels of Mn-addition were compared. Manganese in the water-''tr acts correlated well with the Mn in the plant. Poor correlations of Mn -NH4OAc and Mn-DTPA versus Mn in the plant were found, caused by the f act that the clay increased the MN-DTPA and Mn-NH4OAc, but not Mn in t he plant. The clay contained Mn which was not available. Only the wate r-extracts could be used to assess the availability of Mn. The correla tion coefficients of Mn-DTPA versus Mn-NH4OAc, of Mn-DTPA versus Mn-pr ess-extract, of Mn-1:1.5 volume-extract versus Mn-NH4OAc, and of Mn-1: 1.5 volume-extract versus Mn-DTPA were low. Only Mn-1:1.5 volume-extra ct versus Mn-press-extract and Mn-NH4OAc versus Mn-press-extract gave high correlation coefficients.