Agriculture Reference
In-Depth Information
Regulation UNE-EN-13206 covers three
types of films: (i) standard; (ii) clear ther-
mal; and (iii) diffuse thermal.
Previously, regulation UNE-53328 (now
superseded) defined the durability, in agri-
cultural years, taking solar radiation in
Almeria as a point of reference, whose
annual value was estimated at 148 kLy (kilo
Langley) year
−1
; 1 kLy = 41.84 kJ m
−2
).
At the time of writing, the existing reg-
ulation (UNE-EN-13206) defines three cli-
mate areas as a function of the solar
radiation expressed in kilo Langleys per
year: (i) between 70 and 100; (ii) between
100 and 130; and (iii) between 130 and
160. The anticipated durability of the film
under real conditions is estimated by
means of accelerated artificial ageing,
establishing a correlation between artificial
and natural ageing, depending on the
annual solar radiation of each site (Tables
4.4 and 4.5). Therefore, a film that lasts 2
years in a climate area with 130-160 kLy
year
−1
of solar radiation could last 4 years
in a less sunny climate area of between 70
and 100 kLy year
−1
.
Regulation UNE-EN-13206 defines,
among other properties, the characteristics
and tolerances with regard to: (i) resistance
to traction, tearing and impact; (ii) the ther-
micity (transmissivity to long-wave IR radi-
ation, which is emitted by the Earth's
surface); and (iii) the transmissivity to visi-
ble light (regulated by European regulation
EN-2155-5).
Regulation UNE-EN-13206 is applica-
ble to LDPE, to linear LDPE and the mix of
both, to EVA and to the ethylene and butyl
acrylate copolymers, as well as to their mix-
tures with LDPE.
The designation of a film or covering
film, according to this regulation, must
include: (i) the type (standard, clear thermal
and diffuse thermal); (ii) the polymer used
in its manufacture; (iii) a reference to the
regulation; (iv) the width and thickness;
and (v) the accelerated artificial ageing data.
For instance, the designation of a LDPE
film, of 5000 mm width, 105 mm thickness
with an accelerated artificial durability of
1700 h would be: COVER WITH STANDARD
FILM EN-13206…5000 105 A.
the radiation in the range from 300-400 mm
(Jarvis, 1997). In a similar way, the suppres-
sion of UV radiation around 340 mm limits
the sporulation of
Sclerotinia
and
Alternaria
(Jarvis, 1997).
White fly (
Bemisia tabaci
), vector of the
tomato yellow leaf curl virus (TYLCV), and
thrips (
Frankliniella occidentalis
), vector of
tomato spotted wilt virus (TSWV), are exam-
ples of insects which need UV light for their
visual organs. The lack of UV light limits
their mobility and decreases their presence,
reducing the incidence of disease caused by
these viruses (González
et al
., 2003; Monci
et al
., 2004).
The normal behaviour of pollinating
insects, bumblebees and bees, used in green-
houses is slightly affected by the use of
these anti-pest films, partially affecting their
vision. However, the use of these films is
compatible with pollination by these bees
(Salmerón
et al
., 2001). Further studies are
being conducted in this area.
All these variants of photoselective
films are usually used as part of a multi-
layer, with the aim of incorporating other
interesting properties into the film.
o t h e r
f i l m s
.
The diffusing effect of a film is
induced by specific additives or with addi-
tives used for other aims. These diffusive
films increase the proportion of diffuse light
inside the greenhouse. They have a whitish
appearance, are opaline and their diffusive
power is quantified by their turbidity
(European regulation EN-13206).
Other types of films incorporate fab-
rics inside them or are interlaced with
fabric to improve their mechanical proper-
ties, such as in those used in retractable
roof greenhouses.
Normalization of plastic films used as
greenhouse covers
The Spanish regulation UNE-EN-13206
(
Thermoplastic films for covers used in agri-
culture and horticulture
; the Spanish ver-
sion of European regulation EN-13206) has
replaced Spanish regulation UNE-53328
(
Polyethylene films used as greenhouse
covers
).
