Temporal dynamics of oxygen concentrations in a peat-perlite substrate
2014
Iersel, M.W van | Dove, S.K.
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 (pair) and substrate volumetric water content (Θ) also affected substrate pO2. Substrate pO2 decreased with decreasing pair 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.
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