Abstract
This study was carried out in order to analyse the physical and chemical characteristics of rockwool mat as a carrier of nutrient solution in soilless culture. The volume of the solid phase in the mat was very small (about 3%) . The saturated water capacity was 90% or more, and most of the water in the mat was held at a high matric potential (below pF 1.5) . When the water saturation over the mat was above the range of 50%, the water saturation degree in the deep layer (below 1/2 of the 7.5 cm mat depth) was stabilized at around 70-90%, whereas in the superficial (more than 1/2 of the depth) the water saturation degree showed large variations between 30% and 80%. These variations in the shallow layer may contribute to the supply of air for the plant roots. Excessive drainage caused a decrease and considerable imbalance in the water saturation degree in the mat. And the former saturation level could not be restores by standard drip irrigation. It was seemed important during plant cultivation that a level of 50% or more of water saturation was maintained all over the mat. Since rockwool fiber did not effect significantly the content of PO43-and Ca2+ of the nutrient solution in the mat, such factors can be disregarded in the regulation of the nutrient solution for soilless culture.
