Comparison of water,ammonium acetate,and dtpa to assess the availability of manganese in peat substrate |
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| Abstract: | Abstract An experiment was conducted to assess the suitability of three extractants, water (press‐extract and 1:1.5 volume‐extract), 0.5 M ammonium acetate (NH4OAc) and 0.005 M DTPA for determining plant available manganese (Mn) in peat substrates. Chrysanthemum morifolium was used as a test 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‐extracts 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 fact that the clay increased the Mn‐DTPA and Mn‐NH4OAc, but not Mn in the plant. The clay contained Mn which was not available. Only the water‐extracts could be used to assess the availability of Mn. The correlation coefficients of Mn‐DTPA versus Mn‐NH4OAc, of Mn‐DTPA versus Mn‐press‐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‐extract versus Mn‐press‐extract and Mn‐NH4OAc versus Mn‐press‐extract gave high correlation coefficients. |
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