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  Eur.J.Hortic.Sci. 81 (1) 49-59 | DOI: 10.17660/eJHS.2016/81.1.7
ISSN 1611-4426 print and 1611-4434 online | © ISHS 2016 | European Journal of Horticultural Science | Original article

Reduction of evaporation from plant containers with cover layers of pine bark mulch

R. Anlauf, P. Rehrmann and A. Bettin
Osnabrück University of Applied Sciences, Osnabrück, Germany

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.

Keywords greenhouse production, growing media, HYDRUS-1D, peat substrate, water content

Significance of this study

What is already known on this subject?

  • Evaporation can be reduced by applying coarse materials on top of and between fine materials by interrupting capillary continuity. Simulation models are valuable tools to describe and optimize physical processes in soils and growing media.
What are the new findings?
  • The optimum thickness of cover layers of pine bark to significantly reduce evaporation from growing media is 2 to 4 cm. The physical processes are sufficiently well described with the HYDRUS-1D model (R2 between 0.36 and 0.90).
What is the expected impact on horticulture?
  • The results of the investigation show that pine bark cover layers may help to decrease the negative effect of high evaporation in greenhouses (between 37 and 54% in our investigation corresponding to a reduced energy demand of approximately 1.5 MJ m-2 day-1). The physical system consisting of irrigation technology, growing media and coarse materials can be optimized with the help of simulation models.

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Received: 19 June 2015 | Revised: 4 August 2015 | Accepted: 11 December 2015 | Published: 22 February 2016 | Available online: 22 February 2016

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