Agriculture Reference
In-Depth Information
Photo 10.1.
Decades ago, in certain cases in england, to avoid soil-borne problems greenhouses were
moved from one location to another, in a peculiar form of crop-rotation system.
and the absence of salinity or alkalinity prob-
lems (electric conductivity of the saturated
extract (EC
e
) lower than 4 dS m
−1
with an
exchangeable sodium percentage (ESP) lower
than 10) would be desirable generic qualities,
but these are not always achievable in a hor-
ticultural soil used for protected cultivation.
The soil depth in horticultural crops is
usually not as limiting as in other crops,
due to their smaller root development, pro-
vided that good drainage is available. The
soil depth must be at least 30-40 cm.
The higher the CEC, the higher will be
the buffering capacity of the soil, limiting the
risks of fertilization errors. The organic mat-
ter content is very closely linked to the cli-
matic conditions, which determine the
speed of mineralization, and which is very
relevant to the important nitrogen supplies
it produces. In Mediterranean climates,
organic matter decomposes very quickly
and it becomes a source of nitrogen losses.
As the soil is the source of the essential
nutrients for the plants (N, P, K, Ca, Mg, S
and micronutrients) it is necessary to know
their concentration and availability to plan
a proper fertilization programme.
The salinity of the soils affects plant
growth because it increases the osmotic
potential of the soil solution, and for horti-
cultural cultivation it is advisable to discard
soils whose EC
e
exceeds the threshold of
3-4 dS m
−1
(Dasberg, 1999a), except in extreme
situations and for very tolerant crops.
10.2.3 Considerations on the
In horticultural protected cultivation,
besides the usual soil cultural practices, the
biological status of the soil must be espe-
cially considered (presence of parasites and
soil-borne diseases). The incorporation of
organic matter in the soil (primarily to
improve its physical and hydraulic charac-
teristics) must include efforts to monitor the
salinity and alkalinity conditions along
with the availability of nutrients.
The use of transparent plastic mulch on
a bare soil during the high radiation season
(solarization) has proved to be effective in
reducing the phytosanitary problems origin-
ating in soils, and, in avoiding or decreasing
the use of pesticides.
High soil salinity is very common in
arid regions, especially in coastal areas,
where it is common that the irrigation water
