Agriculture Reference
In-Depth Information
by Wittwer and Castilla (1995), other
objectives of protected cultivation are to:
to provide plant protection (biological
control, for instance). It is possible to
fumigate the soil and the atmosphere,
substitute the soil or use artificial sub-
strates (e.g. growing plants in bags,
rockwool and other sorts of hydropon-
ics), as a means to fight against soil-
borne diseases, pests, nematodes and
weeds. The use of nets or screens to
prevent damage caused by pests is quite
efficient, as is the use of direct covers
with textile or non-woven materials.
Using a mulch for solarization (soil dis-
infection with solar heat) is an efficient
technique without environmental im-
pact, but it is only feasible in regions
that have high solar radiation.
Extend areas of production and grow-
•
Reduce water use
. The use of different
types of mulching (organic wastes,
gravel, sand, plastic film, etc.) allows
for a decrease in water losses by eva-
poration and prevents growth of weeds
(which compete for the available water
in the soil). The use of greenhouses,
tunnels and other forms of protection,
which limit solar radiation, allow for a
reduction in the water requirement of
plants and for a more efficient use of
irrigation water.
Protect crops from low temperatures
•
.
The use of individual forms of protec-
tion for each plant, or plant rows or
whole plots, by means of individual
'caps', tunnels, direct covers or green-
houses, are typical examples. It is worth
mentioning other complementary tech-
niques, with this same objective, such as
the use of wind machines (to mix the air
layers and prevent the stratification of
cold air close to the earth surface where
plants are grown), anti-frost sprinkle
irrigation, smoke generators or the use of
burners to heat open field orchards.
Decrease wind velocity
•
ing cycles
. The use of greenhouses of
varying levels of sophistication, tun-
nels and mulches have increased yields
all over the world enabling horticul-
tural production in new areas and
extending availability of many prod-
ucts outside their traditional periods of
consumption.
Increase yields, improve product quality
•
and preserve resources
. In addition to
the increase in yields achieved with pro-
tected cultivation, the use of resources
(soil, water, solar radiation, energy and
atmospheric CO
2
) is more efficient than
with conventional cultivation. Besides,
with protection against the wind, rain,
hail, cold and the attack of insects and
other pests protected cultivation also
results in a better quality harvest.
Climate control allows for maximiza-
•
. The use of
windbreaks, both hedges and specific
structures made with natural (dried
cane, bamboo) or artificial materials, is
not the only technique to reduce wind
velocity, because other forms of protec-
tion may also provide a very important
windbreak effect (i.e. tunnels and
greenhouses).
Limit the impact of arid and desert cli-
•
•
tion of yields and optimization of prod-
uct quality
. In greenhouses, the
management of temperature and ambi-
ent humidity, as well as atmospheric
CO
2
and light, allow for significant
improvements in the yield and quality
of horticultural products.
Stabilize the supply of high quality
mates
. In greenhouses located in arid or
desert regions, the insulation from the
outside environment allows for the
generation of a proper microclimate for
horticultural production. This is the
case in many areas of the Mediterranean
Basin, the Middle East and Africa,
Australia and America (Mexico, the
USA).
Decrease damage caused by pests, dis-
•
products to horticultural markets.
Protected cultivation avoids many of
the risks of conventional horticulture
and facilitates a regular supply to the
markets, extending the marketing cal-
endars for many species.
•
eases, nematodes, weeds, birds and
other predators
. In an isolated environ-
ment, such as a greenhouse, it is easier
