Plastic covers on crops, along with drip irrigation, are technologies that make it possible to cope with adverse weather conditions and increase production per cultivated area. There are reports of a decrease in the water requirement of crops by 36% under covers in the Azapa Valley, Arica.
Cover Materials Low-cost lightweight structures are a widely used option for all types of coverage, allowing quick laying of structures.
Among the main light structures are those of the Spanish vine type, simple metallic or plastic tunnels.
Structures of greater investment are the greenhouses with a wooden structure and greenhouses with a metal structure for multiple seasons.
Agricultural cover materials are the following:
Plastic covers: Shading nets
Used to prevent sun and wind damage. Among the most used are raschel meshes, as well as metallic meshes such as Aluminet, with a greater capacity to reflect excessive sunlight and with a longer useful life.
It is important that the coverage is less than 30% to avoid excessive shading. Button-type snaps are recommended for proper tensioning.
It is characterized by being a light material for direct coverage use or on stakes or low tunnels. Different weights can be found on the market, the most common being 17 g m-2, with better temperature retention for winter.
Given its low resistance to damage, it is expected to last one to two seasons. In tomato it is used on arches inside greenhouses for early development.
Known nationally as agricultural films for greenhouses, those used in the country correspond to low-density polyethylene (LPDE) in combination with other materials with a thickness between 100 and 200 microns.
Multilayer plastics with EVA have a better transmission of sunlight and higher temperature retention, not being recommended for summer.
In general, they have additives to last two seasons such as HALS, which gives a white color or nickel salts associated with the yellow color. The material has a better survival with an appropriate tension that limits its movement, avoiding direct contact with galvanized steel and wood treated with paraffinic products.
Plastic covers: Anti-aphid mesh 16/10 and 20/10
Covers used for shade houses are made of high-density polyethylene (HPDE). Suppliers approved by the SAG of 20/10 meshes ensure the protection of crops from insect vectors of viruses such as aphids, being required for quarantine and fruit fly.
Despite being more expensive than other plastic covers, they have a useful life of more than ten years. They generate 22% shading; although, being exposed to the elements for multiple seasons, they can generate shading greater than 50%, making it necessary to wash them.
They generate an important microclimate inside with higher relative humidity and low ventilation; irrigation must be controlled to avoid excess moisture in the soil.
Material for fixed greenhouses; its use is not recommended in the central valley as is glass due to its high heat retention capacity; being limiting its use during the summer.