Agriculture Reference
In-Depth Information
for a specific environment and to outline
the plant characteristics that would best fit
the specific greenhouse/environment com-
bination (De Pascale and Maggio, 2008).
Crop rotation is not frequently prac-
tised, and as the majority of cultivated spe-
cies belong to the botanical families
Solanaceae
and
Cucurbitaceae
(with simi-
lar problems of soil-borne diseases), it
would not be effective anyway. Besides,
economic reasons dictate the practice
of monoculture. The diversification of pro-
duction is a desirable objective, but difficult
to reach in practice (Castilla, 2002).
composition. Shading, heat accumulation
and maintaining a low, even temperature
are also important in some cases (Monteiro,
1990). The management of the microclimate
through transpiration control during the
summer can be significantly improved by
means of a dynamic manipulation of venti-
lation, shading and water fogging (Boulard
et al
., 1991).
Strategies for more efficient and eco-
nomic heating include: (i) managing the
night temperatures depending on the wind
conditions in heated greenhouses (Bailey,
1985); (ii) the use of several minimum tem-
perature thresholds during the night (Toki
et al
., 1978); and (iii) the use of variable
minimum night temperatures depending on
the radiation levels of the previous day
(Gary, 1989). Developing and implementing
recommendations for the management of
climate parameters (mainly temperature
and humidity) at a local level, adapted to
the existing greenhouse characteristics, are
necessary.
By comparison with other regions in
the north of Europe, in Mediterranean cli-
mates the selection of species better
adapted to the greenhouse microclimate
(light and temperature) has promoted the
use of members of the family
Cucurbitaceae
,
which are more temperature demanding
than species in the
Solanaceae
. The selec-
tion of cultivars is based on their accept-
ance in foreign markets and local cultivars
are, frequently, left behind; there is a risk
that these genetic resources adapted to
local conditions will disappear. The resist-
ance and/or tolerance to diseases have
induced the use of a greater number of
hybrids. Soil-borne pathologic problems
have enhanced the use of plants grafted on
to
17.5.2
Biological aspects
In Mediterranean greenhouses, the produc-
tion strategies are more focused on biological
aspects of the crops than in highly technical
greenhouses where the focus is on proper
greenhouse climate control (Alpi and
Tognoni, 1975; Tognoni and Serra, 1989).
Breeding programmes have been focused on
improving production, precocity and fruit
set at low temperatures (Nuez, 1986).
Cultivars more adapted to low temperatures,
more resistant to parasites and more efficient
in the use of inputs (water, light, etc.) are
technological tools to save energy in pro-
tected cultivation (Tognoni and Serra, 1989).
Recent developments such as the long shelf-
life tomatoes denote the importance of better
biological knowledge to improve production
strategies. Other aspects with room for
improvement are: (i) the photosynthetic effi-
ciency; (ii) the optimization of plant archi-
tecture to improve the interception and use
of light; and (iii) the intelligent management
of the climate parameters inside the green-
house (Tognoni and Serra, 1989).
tolerant
rootstocks
(mainly
melon,
watermelon and tomato).
The adaptation to low radiation and
temperature conditions has involved a great
diversity of cycles and transplant dates
(Castilla
et al
., 1992). In a similar way, the
periods of excessively high temperatures
are avoided. Sometimes the strategy con-
sists of storing the fruit during the autumn
on the plants (pepper) allowing for their rip-
ening later in the winter (Monteiro and
17.5.3
Strategies and tactical
management
The essential operation in the management
of the Mediterranean greenhouse micro-
climate is ventilation, due to its influence
on the temperature, humidity and air
