One of the possibility that allow costs of soilless tomato culture to be reduced is to reuse the same growing medium. Expanded clay is classified as an inert medium, that is, chemically and biologically passive, although some studies indicate the possibility of the occurrence of exchange sorption and ion adsorption in this medium during cultivation. The aim of the study, conducted in the period 2007–2008, was to determine the usefulness of expanded clay being post-production waste in soilless tomato culture under extended cycle conditions. The study used new expanded clay (I) as the control and expanded clay being post-production waste from year-round tomato cultivation with the following experimental design: chemically sterilized material (II); material washed in water with the remains of the old root system of plants removed and additionally chemically sterilized (III); and material without any modifying treatments (IV). Expanded clay was placed in 12 dm³ poly sleeves and formed in the shape of growing slabs. Crops were grown using a drip irrigation and fertilization system with closed nutrient solution circulation, without recirculation. The nutrient solution was supplied to all plants in the same amount and with the same composition. The study found the lowest total fruit yield (15.10 kg·plant^-1) and marketable fruit yield (14.07 kg·plant^-1) of tomato grown in reused expanded clay without any modifying treatments (IV), whereas this yield was significantly higher from tomato plants grown in the material washed and additionally chemically sterilized (III). Fruits with the highest unit weight (150.8 g) were picked from plants grown in new expanded clay (I), while fruits with a significantly lower weight (138.6 g) were obtained from the treatments with the reused medium both washed and chemically sterilized (III). Fruits of tomato plants growing in reused expanded clay subjected to washing and chemical sterilization (III) contained the highest amount of dry matter (5.71%) and total sugars (3.08% fr.w.), whereas fruits of tomato grown in the new medium (I) had the highest amount of vitamin C (21.96 mg∙100 g^-1 FW), zinc (25.86 mg·kg^-1 d.w) and copper (6.10 mg·kg^-1 d.w).

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