ISHS Acta Horticulturae 761: XXVII International Horticultural Congress - IHC2006: International Symposium on Advances in Environmental Control, Automation and Cultivation Systems for Sustainable, High-Quality Crop Production under Protected Cultivation
GAS CONCENTRATION IN THE ROOT ZONE OF CUCUMBER GROWN IN DIFFERENT SUBSTRATES |
| Authors: | F.G. Schroeder, H. Knaack |
| Keywords: | oxygen, carbon dioxide, substrate, yield, nutrient uptake |
| Abstract:
Inadequate oxygen concentration in the root zone is a constraint to plant growth esp. in hydroponic systems with a limiting root zone. The subject of this study was to get more information about the root zone, mainly the gas composition in growing media, which is used in hydroponic systems. Besides the plant growth parameters of cucumber, yield and nutrient uptake, the results of the gas concentrations in the root zone are presented. Gas sampling at 3 heights from root zone did function well, results ranged from 2000 ppm (0,2%) up to 16700 ppm (1,67%) CO2. Results are significant between the different substrates and measurement spots within one substrate. The inert substrates Fytocell Foam (aminoplast resin foam) contains most CO2. From bottom to the top the CO2 level was increasing. The CO2 level is influenced by root and microbial respiration. But compared with recommended figures the determined CO2 concentration is no limiting growth factor. A new method of monitoring the oxygen level in substrates via fiber optic sensors did function well. The O2-concentration in substrates was determined between 61 and 97% saturation of oxygen. The daily time course was for each substrate different and specific. The results show an influence by the plant activity correlating with radiation and the irrigation schedule. The rockwool substrates contained with about 61% significantly less oxygen than other substrates (Fytocell, peat or compost substrates). O2-level of substrates can be an indicator for oxygen deficiency direct in root zone. During the experiment the O2-concentration varies from the top to the bottom of substrates; for CO2 the opposite trend was found. The artifact of oxygen deficiency correlating with low yield or quality was not found during the experiment. Experiments should be continued with different oxygen levels in substrates due to excess irrigation or substrates with high water content levels to get deficiency conditions for plants roots and significant results. | |
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