Physical and physicochemical properties of the volcanic materials used in hydropony

Abstract

The physical and physicochemical properties of volcanic (basaltic) materials used in hydropony are treated. These materials have a real density of 2.93 g/ml and an apparent density of 0.84 g/ml. The relationship between both densities gives a total theoretical porosity of 71.3 % (v/v). The maximum hydric capacity of these materials was of 63.2 %(v/v) and the difference to the total theoretical porosity (8.1 % v/v) is the occlusive porosity which is considered as a reference for evaluating the extent of disintegration of the particles. The water retention was of 18.6 %, two times greater than that of the gravel. The exchangeable cationic capacity is very low (5 meq/100 g) and the pH of the materials ranges between 7 and 8 units.