Substrate types affect growth, yield and mineral composition of cucumber and zucchini squash

The expansion of hydroponics in many countries of the world in the last few decades may be ascribed to the ability of soilless growing systems to avoid various problems arising from the use of the soil. Cucumber (Cucumis sativus L.) and zucchini (Cucurbita pepo L.) plants were grown in closed-soilless culture under unheated-greenhouse conditions at the experimental farm of University of Tuscia, Central Italy to evaluate the effects of four substrates (rockwool, pumice, perlite, and cocofiber) on growth, yield and plant mineral composition. For both cultures, plants grown in cocofiber, perlite and pumice yielded more than those grown in rockwool. The better temperature regime in cocofiber, perlite and pumice was due to the greater thermal inertia compared to rockwool slabs. The concentration of N in zucchini and cucumber leaves was significantly higher in cocofiber, perlite and pumice in comparison to the rockwool treatment. The concentration of K was significantly affected by the substrate only for the zucchini squash with the highest value recorded on the organic substrate (cocofiber), whereas the Ca concentration was significantly influenced by the growing media only for cucumber with the highest value observed on pumice. Finally, the lowest Mg concentration in leaf tissue was observed on plants grown with the rockwool substrate for both zucchini squash and cucumber. We can conclude that cocofiber, perlite and pumice are suitable for zucchini and cucumber production in closed soilless system, whereas the use of rockwool is more suitable for crops grown under heated greenhouse conditions.