Allowing more light, wider temperature ranges and a higher moisture level is resulting in energy savings without giving up on growth in a number of pot plant species. This is the result of research carried out by Wageningen UR Greenhouse Horticulture with seven different crops.
In the Netherlands some pot plants are grown with little sunlight. Experience in the Energy-producing Greenhouse of Stef Huisman in Bergerden forms the basis of the hypothesis that it should be possible to allow more light without giving up on growth and quality. An experiment to test this hypothesis with various flowering and green pot plants has therefore been set up at Wageningen UR Greenhouse Horticulture. In the study two systems were compared with the standard settings during two subsequent cultivations of about six months.
New settings
The following crops have been studied in the experiment: anthurium, areca, guzmania, calathea, draceana, ficus and oncidium (and dendrobium in the second round). The light level was kept at 300 Watt/m2 in the reference cultivation system, whereas this was 500 Watt/m2 in both other sections; three screening/chalking systems were compared. A moderate temperature regime with a low humidity (40%) was kept in the reference greenhouse and this was compared with wider temperature settings and a high humidity (60 and 80%).
The results show that both experimental setups yielded more growth than the reference greenhouse, with the climate setting with the narrowest temperature ranges giving the best result. It was also found that higher irradiation resulted in the leaves of a poorer green quality of anthurium, areca and guzmania. The colour, however, improved with deceasing irradiation. A low night temperature and a moist climate had a negative effect on the quality of areca and calathea.
The researchers conclude on the basis of these results that there are possibilities for energy saving because allowing more light into the greenhouse results in less heating. But caution is required because differences may exist between cultivars. Extreme combinations of light level, humidity and temperature must be avoided because this may result in damage.
This research is financed by the Netherlands Ministry of LNV (Agriculture, Nature and Food Quality) and the Product Board for Horticulture in the context of the programme ‘Greenhouse as Source of Energy’.