Alkuperäinen teksti - Englanti - Protected cultivation is ...

Protected cultivation is considered to be an intensive
production system requiring relatively high investment
in several aspects of the production and marketing.
However, greenhouses are cropped on an essentially
continuous basis, with no possibility for suitable
rotations, once the limited crop range results in reduction
of soil fertility and rapid build up of soil pests,
which hampers production and requires intensive use of
chemicals