Open Access

Rüdiger Anlauf, Peter Rehrmann, Andreas Bettin

• Evaporation from growing media significantly contributes to increasing the humidity in greenhouses. The effects of a pine bark mulch cover on substrate evaporation was evaluated with different pot experiments. The obtained data have been tested within the water balance model HYDRUS-1D, which was originally developed for mineral soils. Objective of this study was to test the performance of HYDRUS-1D to describe evaporation in plant containers and to evaluate the effect of pine bark as cover layer or layers within growing media. Application of pine bark in combination with peat substrate reduced evaporation up to 50% depending on position, thickness of mulch layer and water content of the substrate. The highest reduction in evaporation was measured in a dry substrate which is covered with 4 cm pine bark. The HYDRUS-1D model describes evaporation from growing media in combination with layers of pine bark correctly as long as hysteresis of the water retention curve and vapor flow is considered in the model.