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An important parameter fordescribing oxygen availability in growing media is the air capacity, but thisparameter does not include any information about the gas exchange with thesurrounding atmosphere. The oxygen diffusion coefficient fulfills thisrequirement and may be better suited as a characteristic parameter to describethe oxygen regime. The measurement of the gas diffusion coefficient is a commonmethod to describe the oxygenation in mineral soils, but this method has notbeen studied well on growing media yet. In this investigation four differentgrowing media were used to measure the oxygen diffusion coefficient at twodifferent bulk densities and four different water tensions in the laboratory. The effect of density andwater tension on the oxygen diffusion coefficient in different growing mediaand the dependence on air content were investigated. The results show that both water tension and density have a majorinfluence on oxygendiffusion. With increasing density and moisture content, a decrease of theoxygen diffusion coefficient can be observed. Between the substrates there areno significant differences regarding the oxygen diffusion coefficient at thesame air content. Based on the oxygen diffusion coefficients of the substrates,the models describing the dependenceof gas diffusion coefficients to air content in the literature were tested forthe transferability to growing media. The Moldrup model 1 shows the best fit.The fit can be slightly further improved by modifying the tortuosity parameter.

KEYWORDS

Gas Diffusivity; Pore Tortuosity; Air Capacity; Horticultural Substrate; Peat

Cite this paper

D. Schmitz, R. Anlauf and P. Rehrmann -Effect of Air Content on the Oxygen Diffusion Coefficient of Growing Media,- American Journal of Plant Sciences, Vol. 4 No. 5, 2013, pp. 955-963. doi: 10.4236-ajps.2013.45118.





Autor: Dominik Schmitz, Ruediger Anlauf, Peter Rehrmann

Fuente: http://www.scirp.org/



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