Iron availability in peat substrates as assessed by water, calcium chloride, ammonium acetate, DTPA and calcium chloride/DTPA

Abstract

An experiment was conducted to find out which extractant for a peat substrate gave the best prediction of iron (Fe) uptake by the plant. Iron was added in four levels (including zero) to peat in the form of either EDTA or sulphate, at two pH levels. Iron from the peat was extracted by water, 0.01M CaCl2, 0.5M NH4OAc, 0.002M DTPA and 0.01M CaCl2 / 0.002M DTPA. The test plant was chrysanthemum. Iron in the plant was determined by total analysis and by o-phenantroline and HCl extraction. Iron additions and pH differences resulted in large differences in Fe content in the peat. Iron contents in the plant were hardly influenced by the treatments. There were poor correlations between Fe in the peat by the various extractants and Fe in the plant. This is probably related to the very small differences in Fe contents in the plant. These small differences could have been caused by the fact that at the low growing rate of the plants during the experiment (winter), also low Fe concentrations in the substrate were enough for the plant. Copyright © 1996 by Marcel Dekker, Inc.