At. Kuiters et W. Mulder, WATER-SOLUBLE ORGANIC-MATTER IN FOREST SOILS .2. INTERFERENCE WITH PLANT CATION UPTAKE, Plant and soil, 152(2), 1993, pp. 225-235
Soil culture experiments were conducted to examine the effects of wate
r-soluble organic matter (WSOM), isolated from the A(h) horizon of a f
orest soil on cation uptake by seedlings of Agrostis capillaris and Si
lene dioica. In contrast to the large effects on soil equilibria, cati
on uptake was only slightly affected by WSOM. Solubilized Al, Fe, Cu a
nd Pb, were not found in higher amounts neither in the Toot nor in the
shoot of the test species. Significant effects were only found for Cd
, Mg, Mn and Zn, where uptake was either enhanced or decreased by WSOM
. An experiment with several standard low molecular weight organic aci
ds affirmed the results obtained with WSOM and supported the hypothesi
s that cations are taken up predominantly in the free ionic form and n
ot as organic complexes. Results are discussed in relation to the effe
cts often found for fulvic and humic acids.