THE INFLUENCE OF THE O2-CONCENTRATION IN THE NUTRIENT SOLUTION ON THE DEVELOPMENT OF CUCUMBER-PLANTS IN A SPECIAL HYDROPONIC-SYSTEM.
Figure 1 shows the scheme of the hydroponic-system we used. Normal plastic tubes of 15 cm diameter, in which holes for the plants were drilled, were put together like a harp. In these tubes the nutrient solution was circulated twice an hour by a pump to avoid gradients of the nutrients or CO2, and to enrich the nutrient solution again with O2. The O2-enrichment was carried out by spraying the nutrient solution in short vertical tubes. As the O2-enrichment was not high enough the solution was additionally aerated by pressed air. The value of the nutrients in the solution was checked by an outlet of used and inlet of fresh nutrient solution. The outlet was controlled by conductivity measurements and a magnet-ventil, the inlet by a niveau controller and a small pump. The nutrient solution was obtained by two water jet pumps mixing two concentrated solutions with water in a relationship of 100 : 1.
As far as possible the nutrient solution was dispensed by industrially produced fully water-soluble compound fertilizers.