EXTRACTION METHODS FOR CHEMICAL QUALITY CONTROL OF MINERAL SUBSTRATES

Substrates should be free of toxins to plants and human beings who consume products from plants grown on these substrates.
For this purpose extraction methods for chemical quality control of substrates, like expanded clay, perlite, sand, pumice and granulated rockwool were studied.
The methods differed in extractants (water and 0.5 M ammonium acetate), grinding and extraction ratio.
Differences in waterholding capacity were taken into account.
The extraction ratio in one of the methods was such that the total amounts of fluid was three times the moisture content at a pressure head of -10 cm.
In the extracts EC, pH, NH₄, K, Ca, Na, Mg, NO₃, Cl, SO₄, HCO₃, P, Fe, Mn, Zn, B, Cu, F, Cd, Mo and Si were analysed.
The data showed that the element contents of the extracts were influenced by the grinding, extractant and extraction ratio.
A method is suggested in which unground material is used with water as an extractant, at an extraction ratio relative to the moisture content at a pressure head of -10 cm.

International Symposium on Growing Media & Plant Nutrition in Horticulture

C. de Kreij, C.W. van Elderen, E. Meinken, P. Fischer

https://doi.org/10.17660/ActaHortic.1995.401.6