Selection Processes of (Changes in) Covered Cropping Patterns

As we saw in the previous sections, greenhouses protect crops from hostile outdoor conditions, so protect against wind, rain, hail and low or high temperature. Therefore they considerably improve crop growth conditions. In this way the growing season can be extended or it can even enable year round production, with production levels outranging outdoor crop production. They are also able to protect crops against insects, harmful by damaging or even destroying the crop or harmful as a vector for viruses. In this respect they also enable biological control of plagues. Moreover, the risk for the development of fungi can be decreased. For these reasons the interest in greenhouse cultivation is not restricted any more to the conventional greenhouse areas at moderate climates, but it is developing worldwide (e.g. Jensen and Malter 1995).