EFFECTS OF HYDROPONICS ON THE DEVELOPMENT OF CUCUMBER GROWING IN ECOLOGICALLY SUITABLE SUBSTRATES

Greenhouse cucumber in hydroponic substrate culture - for example, on rockwool slabs, in containers with perlite, foam or organic substrates - has only limited space available for root growth. Hydroponic substrate culture offers the chance of changing the growth factors in the root zone according to demand.

To make full use of that advantage, it is necessary to examined in such hydroponic systems the development of all plant organs throughout the growing season. For that purpose, root length, root weight (both only in perlite substrate), shoot weight, leaf area and fruit weight were recorded for a spring-planted cucumber crop in perlite, Urea-Methanal-Foam and organic substrates from February to July.

Significant correlations were found to exist between root weight and shoot weight, leaf area and root weight, and root weight and crop yield. Cucumber growing in Urea-Methanal-Foam is not without problems, but with a good earliness, production and ecologically waste disposal.

For a successful soilless cultivation of vegetables in greenhouses we need sufficient supply of nutrient for the different substrates in every step of growth.

On the other hand a surplus of nutrient must be as small as possible. There has been experimental evidence that high crop yields can be reached even with minimal nutrient solution excess (2 to 6 per cent), if the supply of water and plant nutrients was adequately controlled.