OXYGEN SUPPLY IN THE ROOT ZONE OF SOILLESS CULTURE SYSTEMS FOR INDOOR LANDSCAPING

Authors:	H.D. Molitor, M. Fischer
Keywords:	Indoor landscaping, Hydroculture, expanded clay, Seramis®, Oxygen supply
Abstract: The so called “Hydrocultur”-system with expanded clay was tested with regard to the oxygen supply in the rooted zone. In an additional experimental set-up the oxygen diffusion resistance of further two media were detected: the open porous clay granulate Seramis® and a peat-based medium. The oxygen concentration in the flooded zone of the "Hydroculture" system was generally low and even dropped back to 20-30 % of maximum saturation within 24 hours, when the solution was filled up. The oxygen concentration depended strongly on the height of the water layer and was additionally influenced by the application of ammonium nitrogen and its subsequent nitrification. Although nitrate nutrition resulted in higher oxygen values, oxygen concentration rarely exceeded 40 % saturation. This can be attributed to both, the consumption of oxygen by the roots and the mineralisation of root exudates by micro-organisms. High light conditions resulted in lower oxygen saturation in the flooded zone. Independent of the growing system and the different treatments tested, the oxygen concentration in the non-flooded root zone remained at high levels between 90 and 100 % saturation.
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