Plastic Covers and PSA containment - new Retilplast on-field tests
Anti-rain cover tests were carried out in Cisterna (Latina - Italy) in the following companies: F.lli Quaranta, Saccone, Duras, Decastro and azienda agricola Gullino.
Both golden (Soreli) and green (Hayward) varieties were covered and five hectares of golden kiwis (Y-356) were also covered in New Zealand.
In an interview, Walter Ruggia, R&D manager for Retilplast, said that "our objective is also to contain the cost of structures and analyse the quality of the light that filters through covers."
The cost to modify existing anti-hail structures so anti-rain films can be installed are rather low:
• In case of flat-roof structures (Cisterna and Latina), 2,000 metres of Ø4 ÷5mm steel wire are needed for every hectare - estimated cost €700.00 plus installation costs.
• In case of pyramid structures (Northern Italy), 4,000 metres of Ø4 ÷5mm steel wire are needed for every hectare - estimated cost €1,400.00 plus installation costs.
Companies and technicians feel that results for golden kiwis were positive as far as bacteriosis containment went, but we still have to wait a few more years to be certain.
As regards the agronomic aspect, a slight delay in ripening was detected.
7 fruits cultivated under plastic covering and 7 open-field fruits of the golden Soreli variety were chosen to compare the Brix level:
• The Brix level under covers varies between 5 ÷ 6.7 = 5.9 average
• The Brix level in open-fields varies between 5 ÷ 8 = 6.7 average
• A difference of 0.8 Brix was registered.
In the photo, a comparison between non-covered kiwis (left) and kiwis covered with Poly Film-MS (right).
Among other differences noticed there were the more uniform grades and Brix levels as well as the peel and flesh colour of fruit cultivated under films.
In the photo, a comparison between open-field kiwis (left) and kiwis covered with PolyFilm-MS (right).
Dry matter of Soreli kiwis was:
• Covered fruit = 16.70
• Open-field fruit = 15.61
The structures
"When choosing the type of film to use for covers, we tried not to change the quality of light, as the objective was to maintain it as close as possible to open-field light." Two types of covers were therefore chosen:
• A high-resistance diffused light thermal film (PolyFilm-150-MS).
• A plastic-coated fabric (Nuovo-Politex-150).
For what concerns bacteriosis, test results have been very satisfactory for both types of covers - Poly-Film-150-MS as well as Nuovo-Politex-150.
They are very easy and quick to install. In addition, thanks to the hinge clip applied to one edge and the elasticated tie-down string on the other edge, the system is very resistant against wind when the structure is perfectly tensioned.
The films installed in the Cistena area had to endure 100km/h winds for almost six hours on various occasions and neither the structure nor the films were damaged.
When installed flat with a 0÷40cm gap between covers at the centre of the row, the advantages are as follows:
• More room for plants;
• Uniform light;
• Better air circulation, thus preventing condensation from forming.
Closing and opening operations were also simplified.
PolyFilm-150-MS (Multi-Strati) is also used to hasten harvesting and improve the quality of fruit. Thanks to its characteristics (transmittance, diffused light, thermal, resistance), it creates a balanced microclimate that improves photosynthesis and enables to grow bigger fruit that is more compact and appealing. It is being increasingly used by international companies.
Nuovo-Politex-150 is a plastic-coated high-density polyethylene fabric (HDPE), so it is water-proof. It can therefore maintain temperatures cool during summer, as can be seen from the following chart:
Comparison chart between open-field temperatures (above, in °C) and Politex temperatures (below, in °C)
For further info:
Retilplast srl
Area Industriale, uscita A3
84022 Campagna (SA) - Italy
Tel.: +39 0828 45359
Fax: +39 0828 48127
Email: [email protected]
Web: www.retilplast.it