Growing media physical properties: should gas diffusivity and respiration rates parameters be included?

There is a trend in growing media characterization to include dynamic as well as static properties for growing media characterization. With respect to aeration processes, air-filled porosity and oxygen content are thought to reveal potential aeration problems. However, previous work on gas diffusivity has shown that the gas exchange dynamics may be more likely to control the aeration process, than merely the storage of air within the porous medium. This paper presents additional results using respiration rate and diffusivity measurements. Results and models showed that the lack of aeration is better described by measuring respiration rate and gas diffusivity rather than change in oxygen content, as the oxygen content may take long time to manifest despite the existence of aeration limitations in growing media. Therefore, this paper proposed using the two parameters (gas diffusivity as well as respiration rates) to anticipate possible aeration limitations within growing media, as macropore dominance in substrates is so large that measuring oxygen depletion does not fully describe the process in meso and micropores.