TEMPORAL DYNAMICS OF OXYGEN CONCENTRATIONS IN A PEAT-PERLITE SUBSTRATE

Anoxic conditions in soilless substrates have been implemented in disease development, reduced growth rates, and denitrification, but there is little quantitative information on oxygen concentrations in soilless substrates.
We measured the partial pressure of oxygen (pO₂) in peat-perlite substrate planted with petunia (Petunia × hybrid). There are distinct diurnal fluctuations in substrate pO₂, and these can be largely explained by changes in substrate temperature, which increase the amount of water vapor in the air in the substrate, diluting oxygen and other gases.
Barometric pressure (p_air) and substrate volumetric water content (Θ) also affected substrate pO₂. Substrate pO₂ decreased with decreasing p_air and with increasing Θ. Photosynthetic photon flux had a highly significant, but small effect on pO₂. Substrate density had no significant effect on pO₂. Overall, substrate pO₂ was between 19.1 and 20.6 kPa, even after watering the substrate to container capacity.
The high air-filled porosity of the substrate (approximately 0.40 m³•m^-3 after irrigation) may have prevented the development of anoxic conditions.
Since such high levels of pO₂ are unlikely to induce any detrimental anoxic effects on plants, our data do not provide any supporting evidence for the idea that anoxia is an important potential problem in peat-perlite substrates.

International Symposium on Growing Media and Soilless Cultivation

M.W. van Iersel, S.K. Dove

anoxia, Petunia × hybrid, substrate volumetric water content, substrate temperature, vapor pressure

https://doi.org/10.17660/ActaHortic.2014.1034.44