Agriculture Reference
In-Depth Information
•
Transpiration requires energy for the
(i) When to irrigate?; and (ii) How much
water to apply?
The usual methods to schedule drip
water evaporation process, which
mainly comes from the sun. Greenhouse
heating also contributes to the evapora-
tion process.
The maximum transpiration values
•
irrigation in greenhouse soil-grown
crops are: (i) methods based on climate
parameters to estimate the ET of the
crop; (ii) methods based on soil para-
meters (tensiometers mainly); and
(iii) methods based on plant parameters
(seldom used).
For soilless crops, the most usual meth-
•
in greenhouse tomatoes in the
Mediterranean area are of the order of
6 mm day
−1
, although hourly rates of
1-1.5 mm may be possible.
Soil water relations are characterized
•
•
by its water retention capacity and by
its water potential (energy status of the
water in the soil).
The water content in the soil is usually
ods are: (i) methods based on climate
parameters to estimate transpiration;
and (ii) methods based on substrate
parameters (tensiometers, level sensors,
weighing devices).
The different irrigation scheduling
•
quantified by its moisture content
(gravimetric or volumetric), by the read-
ily available water and by its matrix
potential or matrix tension.
The most usual sensors used to meas-
•
methods, in both soil- and soilless-
grown crops, can be complementary.
The
•
•
water
use
efficiency
(WUE)
ure the water in the soil are tensio-
meters, which measure the matrix
tension (absolute value of the matrix
potential) in the soil.
Characterization of the water status of
defines the production (photosyn-
thetic, biological or economic) per
water unit (transpired, evapotranspi-
ration or applied).
In greenhouses, the WUE is, at least,
•
•
the plant (using methods based on
measurements of the size of plant
organs, of the sap flux, plant tempera-
ture, etc.) for irrigation scheduling is
not common in practice.
The guidelines to evaluate the irriga-
double or triple that of the open
field.
Fertilization of horticultural crops
•
must be based on replenishing the
nutrient taken up by the crop, cor-
rected as a function of the application
efficiency, and avoiding excessive sup-
plies that can generate aquifer contam-
ination by leached nutrients and soil
salinization.
The salinity tolerance level of vegetable
•
tion water quality are based on its
electric conductivity (EC), which
depends on its dissolved salts con-
tent, and the SAR (sodium absorption
ratio) (Table 11.9). Both indexes quan-
tify the capacity of salination (EC) or
alkalization (SAR) of the irrigation
water.
When a plant suffers water deficit or
•
crops involves a decrease in yield when
the tolerance thresholds are exceeded,
in the water or in the soil.
Fertigation, joint application of irriga-
•
•
stress its growth slows down, possibly
negatively affecting the yield, if the def-
icit is sufficient.
Nowadays, the most common green-
tion water and fertilizers (dissolved
in the irrigation water), is compulsory
if localized irrigation systems are
used.
Irrigation of soilless crops requires
•
house irrigation systems are the high-
frequency localized irrigation (HFLI)
systems (drip and similar), which
require different management to that of
conventional irrigation systems.
Irrigation scheduling involves giving
•
special management: supplying an
excess of 20-30% of water, and, try-
ing to maintain pre-fixed values of EC
and pH in the nutrient solution. The
analysis of the drainage solution (EC
and composition) allows for adjusting
•
a response to two basic questions:
