Agriculture Reference
In-Depth Information
However, it must be pointed out that
the most technologically advanced and
most productive greenhouse industries are
centred in northern colder countries (e.g.
The Netherlands, Belgium, Canada, Japan).
The main reason for the survival of the
greenhouse industries of the north in an
increasingly competitive world market is
that, despite the high heating costs, and
contrary to public misconception, it is
cheaper to heat a space than to cool it and
this offers better opportunities for year-
round production in the north than in the
south. In reality, it is not possible to con-
trol the greenhouse air temperature within
acceptable levels during the summer
months in hot climates with present green-
house cooling systems. In turn, the good
prospects for year-round production (and
much higher yields, of stable product qual-
ity) allow for investment in more expen-
sive (and more sophisticated) greenhouses
in the north.
Pot plants are more limited in where
their production areas can be located due
to their high transport costs. In a similar
way, species such as roses, which need
strict climate control to obtain high qual-
ity flowers, must be cultivated in green-
houses with a good level of technological
equipment. Sometimes the commercial
aspect, such as when produce is sold
directly to the final consumer, may dic-
tate the construction of the greenhouse in
specific locations, such as peri-urban
areas.
The trend to suppress political and
geographical borders, and the consequent
restriction on barriers for export (agree-
ments of the World Trade Organization,
WTO), will have implications in the long
term with regard to the prevalence of hor-
ticultural areas with higher production
efficiency, which are able to adapt them-
selves to the requirements of the market.
The phytosanitary barriers (limits placed
on the export of produce due to pesticide
residues, or the possibility of introducing
pests or pathogens from the exporting
country) are expected to become even
more relevant than they are today in this
sector (Castilla
et al
., 2004).
Given the need for export, and the great
importance that the external market has in
countries with a well-developed horticul-
tural sector, it is expected that in the future
international competition will increase and
will become an even greater challenge.
4.4 Climatic Suitability for
4.4.1
Introduction
Today, technology allows greenhouse culti-
vation of any horticultural species in any
region of the world, provided that the green-
house is properly climatized, but a profit-
able cultivation of the target crop requires a
much more strict selection of the region,
depending on its climatic conditions and
the requirements of the selected horticul-
tural crop.
Solar radiation is the first climate
parameter to be considered when evaluat-
ing the climate suitability of a region for
protected cultivation. The length of the day
and the global solar radiation intercepted by
a horizontal surface through the daytime
hours (see Chapters 2 and 3) determine the
total daily radiation (global solar radiation
integral in that period). The ambient tem-
perature is another basic climate parameter
to consider.
The stability of both values (radiation
and temperature) through the different
months of the year enables the representa-
tion of their average monthly values
(obtained by averaging data sets for several
years) for a given location, in a climate dia-
gram with an elliptic shape, which repre-
sents the location's climate (Fig. 2.15).
Other climate parameters, such as soil
temperature (which is linked to the air
temperature), wind, rainfall and air compo-
sition (humidity and CO
2
), should also be
considered, although their influence is not
as
important,
when
evaluating
climate
suitability.
Depending on the climate characteris-
tics of a region and the requirements of the
crops to be grown it will be necessary to
