Viresco®: a biotextile for the for grassing over critical terrains
(da ACER n.1/97, p.57, di M.Borin Dip. Agronomia Univ. di Padova, C.Marchetti
Studio Agronomico e di progettazione, A.Galgaro, Dip. Geologia e Geofisica, Univ. di Padova)
New patented technology for grassing over and stabilizing
critical land surfaces.
Viresco®
preliminary results show
that, thanks to its versatility and flexibility, this biotextile
may be used on all kinds of terrain.
Viresco®
is a biotextile composed of a layer of cellulose
fibres, inside which are embedded seeds of various vegetal species.
These are stable and do not change their position during
emplacement or later. The special conformation of
Viresco®
means that various sizes of seeds and other materials, including
fertilizers, can be inserted in it. Using
Viresco® simply
involves laying it in place and watering it, so that it sticks
firmly to the surface of the soil and the seeds contained in it
can germinate favourably.
Between October 1995 and September 1996, the performance of
this new product was tested on particularly difficult terrain.
The test area was in the Euganean Hills in the province of Padova
(north-east Italy), characterized by a considerable gradient
(100% slope), a northern exposure, and a substrate composed of weathered
rock.
Testing
In this environment, the performance of
Viresco® was
compared with that resulting from simple manual sowing of herbaceous seed,
both on bare soil and on bare soil covered with a
jute mat. Two mixtures of seeds, suitable for the soil and climatic
conditions in question, were used in each case. When testing
Viresco®,
treatments involving the presence or absence of
25 g/m2 of artificial fertilizer with slow-release nitrogen were
compared. 50 g/m2 of seeds were used for each test. The biotextile
was 0.7 cm thick and weighed 100 g/m2.
Tests began on October 6 1995.
Viresco®
laid in place
and seeds were sown on bare soil on a slope without vegetation,
the earth having previously been slightly roughened by raking. As
soon as it had been laid,
Viresco®
was watered with 1.5 litres
of water per square metre. The period immediately after laying
was particularly dry, with a sharp fall in temperature at the end
of November and minimum temperatures under zero.
The main results of the experiment were as follows:
- germination and rooting phases were slowed down by the presence
of Viresco(R), due to the small space existing between the seeds
and the soil before the rootlets could reach and penetrate it.
This disadvantage may be minimized if the mat is watered suffi-
ciently, so that it adhers better to the surface of the ground;
- emergence with
Viresco®
was more uniform and denser than in
the other test cases. Seeds sown on bare soil were often lost,
due to the high slope;
- the possibility of inserting fertilizer inside
Viresco® meant
that seeds grew with greater vigour, favouring more rapid growth
in relatively poor pedo-climatic conditions. The last check, made
just before the onset of winter 1995, showed that the addition of
fertilizer led to the best growth conditions;
- in May 1996, only the case of
Viresco®+fertilizer revealed
normal development of vegetation, bright green in colour and with
approximately 100% cover. In all the other cases, growth was
poor, and vegetation was yellowish-green, with bare patches;
- during spring and summer 1996, the vegetation with
Viresco®+fertilizer
grew so much that mowing was necessary in
early August;
- in non- Viresco®
areas where the vegetation grew normally, thickness
fell by 50% during the course of the year. In areas with
Viresco(R) degradation was slight;
- the presence of
Viresco®
was able to reduce erosion to a
remarkable extent. The immediate attachment of the biotextile to
the soil after emplacement and the fact that it remained in place
well after germination and plant development meant that soil
losses were efficiently reduced, and the soil itself was protected
against both leaching and surface runoff.
In the light of these preliminary tests, undertaken in
particularly difficult conditions as regards substrate and cli-
mate, we may state that
Viresco®
is an innovative product of
naturalistic engineering, and may be used with positive effects
in situations in which grassing over, consolidation and deep
stabilization operations are required (fencing, picketing, containing
walls, etc.). The flexibility of the product also indicates other
applications. If our tests, carried out in a natural
environment subject to all the climatic and mechanical factors of
a typical micro-ecosystem, represent the "average" situation in
which Viresco®
should be used, its versatility may allow
personalized or customer-designed versions, according to the specific
environment in which it is applied.
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An example of te results obtained with
con Viresco®:
excluding the one week germination delay, the grass then grows fast, robust and wealthy.
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An experiment compared the effect and the better resistance of a seeding
with Viresco®
compared to a grassing using the hydroseeding technique.
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