CONDITIONING IN AN ORGANIC GREENHOUSE

Abstract

Organic growers in the Netherlands have to cope with ambitious goals for the emission of CO2, which in practice requires that less fossil fuel is used for heating. With conditioning, the greenhouse air can be cooled and/or dehumidificated mechanically, so that excess summer heat is collected and can be stored in aquifers for reuse with the help of a heat pump in winter. The required energy can be provided through green electricity instead of fossil fuel for heating. Experiences with closed greenhouses have shown that mechanical cooling lowers the need for ventilation, thereby decreasing the CO2 emission and pest pressure. In addition, conditioning can give a more balanced indoor climate and allows for a better management of humidity, which greatly reduces the chance of outbreak of Botrytis and similar diseases. Wageningen UR Greenhouse Horticulture is carrying out a dedicated research with an organic grower who operates a conditioned greenhouse. In this project, the main objective is to find out in what way the advantages of cooling are helpful, or can be improved for organic production, in view of the very strict requirements about application of plant protection chemicals. Conditioning an organic greenhouse may give higher yield and a better control of diseases and insects, but not enough references are available to give a significant comparison.