Cherry tomato yield on two different solid growing media

Rockwool (RW) is largely used, in soilless culture, for growing tomato, but because of its high cost, high needs (from about 90 to 120 m(3) per hectare) and for environmental reasons (growers are responsible for the disposal of waste materials), growers are involved in finding new media that substitute RW without negative effect on quantity and quality of tomato yield. "Pozzolana di Barile" (BP) (commonly used as building material), is a mine material of volcanic origin, characterized by a relatively small dimension of the grains (61.4% are between 5.01 and 10.00 mm, and 31.0% are bigger), that was tested as an alternative growing medium for soilless culture because it is sterile, chemically inert, physically stable and drains easily. The trials were carried out in Southern Italy in 2000 and 2001 in the Metaponto area (40 degrees 20' N; 16 degrees 48' E), in which growing tomato in soilless culture is increasing. Two medium-In cycles of cherry tomato with 'Naomi' were performed, with a density of 2 plants m(-2); plants were grown with two stems and topped at 9 trusses. In the experimental conditions, plants on BP yielded 3499 g of total fruits per plant, about 608 g less than those on RW; on the other hand, some qualitative traits of the production (i.e., truss conformation and flesh firmness), were not affected by the growing media, but others, such as, dry matter content, total soluble solids, ascorbic acid content and average fruit diameter, increased significantly on BP media. Results showed that BP can be considered suitable for the cultivation of cherry tomato, but its low water holding capacity may be critical with an inadequate management of the fertigation. Furthermore, the validation of this natural, sustainable and economic growing medium could be proposed by setting up appropriate management techniques (i.e., frequency of fertigation, mixtures with other media, etc.), in order to overcome some limiting characteristics of the substrate.