DISTRIBUTION OF NUTRIENTS AND WATER IN ROCKWOOL SLABS

During the 1980s, soilless cultures expanded enormously. Since then, s everal kinds of substrates, both biodegradable and non biodegradable, have been developed. In this research, the physicochemical characteris tics of one of the most commonly used chemical inert substrates 'rockw ool' is investigated. The flow patterns occurring in rockwool slabs un der both laboratory and practical situations were investigated, using a pigmented nutrient solution. As the rockwool slabs became more satur ated, flow patterns were spread more horizontally. The horizontal and vertical EC and pH gradients present in rockwool slabs under practical situations are represented in figures for a tomato crop. Both horizon tal and vertical EC gradients with a magnitude of 4 mS/cm are present. Below the plants, the pH in the slabs is lower, while there is almost no pH gradient in the vertical direction. The distribution of ions in rockwool was studied under laboratory circumstances as a function of the moisture content of the slab, the fertigation time, the fertigatio n volume and the vertical position in the rockwool slab. The moisture content of the slab, the fertigation volume and the vertical position in the rockwool slab affect the distribution of ions in the slab. (C) 1998 Elsevier Science B.V.