Various irrigation treatments were studied to determine their effects on the water and aeration conditions of peat-based growth media and evaporation from these media. Low-humified sphagnum peat and a mixture of this peat and perlite (in containers) were subjected to three contrasting irrigation treatments in which the container capacity was used as a target water content. The more frequent the reirrigations and the lower the vertical position within containers, the higher the matric potential of the growth medium averaged. Furthermore, the higher the water content of the growth medium, the higher the mean evaporation was from the containers. Within each irrigation treatment, slightly more water (on average) evaporated from the peat than from the peat–perlite mixture. Due to higher water retention and shrinkage during drying, a pure peat growth medium may increase the risk of waterlogging and, hence, O2 deficiency for containerized plants if plants are irrigated frequently to container capacity. To prevent waterlogging and high water loss by evaporation, low-humified sphagnum peat can be irrigated relatively infrequently (especially at low evaporation rates) and thoroughly within a short time (especially at high evaporation rates).
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