Agriculture Reference
In-Depth Information
the environmental impact of the drainage
solution/water, although using such a sys-
tem requires the availability of good quality
water and/or high investment.
•
Soilless crops, in addition to their
higher installation costs, require pre-
cise monitoring to avoid failures in the
water and nutrient supply, which could
be disastrous given the low inertia of
these systems.
Crops grown in solid substrates are the
10.5
Summary
•
most prevalent in greenhouses, with
perlite, rockwool, sand and gravel as
the most popular substrates. Other sub-
strates used are coir (coconut fibre),
peat, bark and expanded clay.
The main physical characteristics of a
•
The choice of the location of green-
houses has been based, mainly, on cli-
matic conditions and if the soil was
not suitable in the chosen location, it
was improved, even creating an artifi-
cial soil.
Although modern high frequency irri-
•
substrate are porosity, water retention
and availability, and air content.
The readily available water in sub-
•
gation techniques limit the function of
the soil as a water and nutrient reserve,
a soil with good physical, chemical and
hydraulic
•
strates is retained in very limited and
narrow margins of matrix tension.
A good substrate, besides having good
characteristics
is
always
•
preferable.
High salinity is a common feature of
physical characteristics and stable
chemical properties (or ideally being
inert), should be biologically stable and
inexpensive.
The most common substrate growing
•
arid region soils, where many of
greenhouses are located, and this is
aggravated by the use of more-or-less
saline water for irrigation. The absence
of rain inside greenhouses decreases
the possibilities of combating salinity.
Some techniques like mulching or
'enarenado' (sand mulching) allow
cultivation in soils with slightly
saline water without compromising
production.
Soilless cultivation allows for the
•
systems in Mediterranean greenhouses
are ditches, gutters (supported or ele-
vated), slabs and bags. The choice of
the substrate determines the system to
be used and vice versa.
Closed systems, which recirculate the
•
drainage water, require good quality
water. These systems avoid the envi-
ronmental impact of eliminating leach-
ate, but the recirculating water must be
disinfected, to prevent the propagation
of diseases.
The negative influence of salinity in the
•
development of the plant roots in a
medium (solid or liquid) isolated from
the soil, and thus, avoiding soil-borne
diseases.
The reasons for the expansion of soil-
•
•
production of soilless crops may be
minimized with proper climate control.
The main traditional functions of the
less crops, besides the prevention of the
soil-borne diseases, has been the good
agronomic performances derived from
better control of the water supply and
mineral
•
root media (water storage, nutrient sup-
ply and plant support) have lost rele-
vance in modern (soilless) greenhouse
production systems.
nutrition,
and
good
root
oxygenation.
