Agriculture Reference
In-Depth Information
10
10.1
Introduction
10.2
Desirable Characteristics of
Horticultural Soils
Normally the location of the greenhouses
is based, primarily, on the local climatic
conditions, with little relevance to the soil
qualities of the chosen location. If the soil
was not appropriate, an extreme remedy
would be to create an artificial agricul-
tural soil, a frequent situation in some
areas of south-east of Spain and some
parts of the Canary Islands, where the
crop profitability allowed for such an
intervention.
The problem of soil exhaustion, in
many cases due to monoculture, decades
ago induced the system of greenhouse
'rotation', displacing them by means of
special devices (Photo 10.1) or simply
changing their location (usual in tunnel-
type
10.2.1
Physical and hydraulic
characteristics
Although modern high-frequency irrigation
techniques notably limit the basic function
of soil being a water and nutrient store,
a loamy or loamy-sandy textured soil would
be most appropriate for horticultural crops,
ideally composed of around 50-60% sand
and well supplied with organic matter.
A texture of this type with no gravel, stones
and boulders and that is well balanced chem-
ically, normally has good hydraulic and
chemical characteristics (see Chapter 11).
A proper structure provides for good por-
osity (basic for the root aeration) contribut-
ing to a balanced permeability which is so
necessary in protected crops.
An aspect that is often neglected is the
drainage conditions of the greenhouse soil.
If necessary, the soil should be provided
with an artificial drainage network.
greenhouses,
in
the
north
of
Africa).
A later innovation was the use of inert
substrates and the development of soilless
crops, which insulate the root media from
the soil, notably limiting soil-borne disease
problems.
The water and nutrient reserves of a
good horticultural soil are higher than
those of a substrate, and so the margin of
error is much smaller when growing in
substrate.
10.2.2
Chemical characteristics
A proper cation exchange capacity (CEC),
a balanced pH (from 6.0 to 7.5, if possible)
