poster - International Conference of Agricultural Engineering

enchmarking exercises. Nevertheless, there is not a single set of performance
indicators that can satisfy the standardization criteria from every standpoint.
Therefore, primary data can be used to produce a large number of secondary data
and performance indicators, then can be analysed in different ways following the
prevalent standpoint (e.g. economic instead of environmental, etc). In the present
paper we will present results based on the following indicators:
a) Measured yield normalized on the local potential yield (t ha -1 / t ha -1 ).
Actual crop yield
Relative yield =
Potential crop yield
b) Relative water productivity (t/m 3 )
Potential crop production
Relative water productivity=
Total water supplied
c) Production value of land (kg/ha)
Total yield (kg)
Productive efficiency =
Irrigatedarea ( ha)
The above three indicators were calculated based on experimental data from a pilot
farm. The experimental work was carried out in a single- span, arched roof,
greenhouse covered by a single polyethylene film (type PE-EVA-film TUV 3945, film
thickness of 180 μm) N-S oriented, near Volos (Velestino: Latitude 39º 22΄, longitude
22º 44΄, altitude 85 m). The internal of the experimental greenhouse was properly
adjusted so that the closed hydroponic system to be installed. The geometrical
characteristics of the greenhouse were as follows: eaves height of 2.4 m; ridge height
of 4.1 m; total width of 8 m; total length of 20 m; ground area of 160 m 2 , and volume
of 572 m 3 . The greenhouse soil was totally covered by a plastic covering permeable
to water.
The tomato crop (Licopersicon esculentum, cv. Belladonna) was transplanted during
23 December 2010 and will remain in the greenhouse until mid July 2011. The plants
are grown hydroponically in rockwoll bags (1 m long, 0.2 m wide, 0.075 m high). The
plant density is 2.4 plants∙m -2 . Plants are laid out in four double rows; the two outside
rows are used as borders while the six internal lines are used for the treatments
studied.
Three treatments were studied:
a) open system, no recirculation of the nutrient solution
b) closed system, complete recirculation of the nutrient solution, addition only of
water and nutrients absorbed by the plants
c) semi-closed system, recirculation of the nutrient solution until certain set
points are reached.
The set points were: EC of the nutrient solution higher than 5 dS m -1 or Na+
concentration in the nutrient solution higher than 15 mmol l -1 . The first time to drop
out of the system drainage solution was when Na+ concentration in the system was
higher than 25 mmol l -1 and after this set point was reached, Na+ concentration was
set to be lower than 15 mmol l -1 . If the above set points were not reached, the system
added water and nutrients absorbed and recycled the solution.
3. Results
3.1. Study area
Thessaly is located in central Greece and is a plain region surrounded by Mount
Kisavos and Mount Pelion in the east, along the coast of the Aegean Sea. Thessaly’s