Minimaliseren verdamping tulp : factoren om rekening mee te houden bij het ontstaan van kiepers

Energy use in well insulated areas for hydroponic tulip forcing in multiple layer systems, lighted by LED’s, is determined by transpiration. Reduced transpiration when Relative Humidity (RH) is high (RH> 95%) risks to result in topple. In the program “Greenhouse as Source of Energy” research of WUR showed extended cold treatment before forcing and bulb size to increase topple. At a greenhouse temperature of 14oC the start of the topple sensitive phase is delayed compared to 18oC, but ends the same day. If forcing starts at 14oC but is later continued at 18oC the percentage of unaffected tulips is reduced strongly, whereas starting at 18oC and continued at 14oC topple is less. Fertilisation with Calcium during both rooting and forcing results in the highest portion of unaffected tulips. This effect of Calcium is the strongest when forcing starts at a RH≈70%. The backgrounds of a batch of a cultivar, as cold preparation and bulb size, has to be known in detail in order to be able to reduce energy use by reducing transpiration.