It is especially important with tall vegetable crops. Research has shown that diffused light also reduces fungus spore development and insect propagation. Light transmission Photosynthetically active radiation PAR light transmission varies with the type of film additives. Dust, smog and plastic deterioration can also reduce light transmission. Some growers replace their plastic every year just to get a few percent higher light level when growing during the short days of winter.
Some manufacturers make a film with anti-static properties that repels dust, dirt and smog. Photoselective films Photoselective films absorb or reflect specific wavelengths of light. They can enhance plant growth, suppress insects and diseases and affect flower development. They have also been shown to improve rose yield and quality. Single or double layer For normal operation, a single layer of film is adequate. If a grower is operating a greenhouse during the heating season, an inflated double layer is desirable.
The double layer reduces heat loss at night by about 40 percent. It also reduces the stress at the attachments and the rippling of the plastic on a windy day. A slightly higher pressure should be used in windy or snowy weather.
Connecting the blower to use outside air will reduce condensation between the two layers. Plastic failure Early failure of polyethylene film can be attributed to attachment stress, abrasion on rough surfaces and sharp edges or heat build-up in the area of rafters, purlins and extrusions. Contact with chemicals from pesticides or pressure treated lumber can also affect the life of the plastic.
Polyethylene may also be subject to cuts from blowing ice especially if there are multiple greenhouses adjacent to each other. A scrim reinforced poly may be desirable in these situations. John Bartok Jr. Water issues were a major focus of the conference, including water quality related to pathogens that reside in water and the impact a water source can have on pH and nutritional management.
Growers in areas of the country that recently experienced drought conditions and restricted water use know firsthand how important a reliable source of water is to the survival of their business.
Growers in the Southeast have been especially hard hit the last few years suffering through severe drought conditions. During nearly 50 percent of the country was experiencing some type of drought. The changing landscape The issue of water availability is expected to become an even bigger issue as the federal courts put increasing pressure on the federal EPA to begin stricter enforcement of the Clean Water Act. The result is EPA has proposed more stringent regulation of nutrient water quality standards for Florida.
EPA is also looking to begin to enforce limits on storm water pollution that will have a major impact on how cities deal with runoff. USA Today reports these more stringent limits could force cities to make major changes in road construction and residential and commercial development including landscaping.
The paper said local governments, which are facing mounting budget deficits, are putting more of the financial burden of maintaining storm water systems on residents and businesses. One city that has taken a proactive sustainable approach to storm water management is Portland, Ore. Its Green Streets and Ecoroof programs are aimed at reducing storm water runoff. The city has about 50, homeowners who are directing runoff from rooftops into gardens and rain barrels.
The city is also offering financial incentives to property owners and developers to install ecoroofs. The city has of these roofs that cover 24 acres. Expect our industry to receive more pressure to reduce runoff with a great opportunity for our product to be part of the solution.
The Alcea rosea annua Spring Celebrities series from American Takii is a multi-use plant that can be grown as a cut flower, used in large containers or planted in the landscape. Three new colors are being introduced this year: Crimson, Lilac and Pink.
Plants are quite cold tolerant, though flowers will be damaged by frost. In the garden plants take full sun, are drought tolerant and attract butterflies. Vietnam India Nigeria. Water-based Air Heating.
Cooling Fog System Fogger. Cultivation work at height Harvesting Trolleys. Consulting Training. News Articles. Plastics for Greenhouses One of the main characteristics of greenhouses is the use of plastic as a enclosure material, except for the Venlo-type or Dutch greenhouses which use glass.
An example of plastic widely used in greenhouses is 3 years thermal plastic, which has the following characteristics: Blade made of three-layer LDPE coextrusion white translucent: Outer Layer : durable and non-stick, has additives against UV radiation Middle Layer : Thermal, high EVA content, providing thermicity.
Vinylacetate ethylene copolymer EVA The EVA films are widely used for covers, double covers as heat shield and in the protection of low tunnels. As expected from a polycarbonate panel, the Macrolux Greenhouse Cover is far from being the cheapest option in the market. With a thickness of 10 millimeters, this tarp is much thicker than any standard plastic sheet.
The main matrix of the tarp is transparent, with enough area to allow substantial sunlight to shine through. A mesh weave that runs through the whole extent of the tarp greatly enhances its rigidity and durability without adding much weight or compromising its transparency. The edges of the tarp are heat-sealed, and the corners are double-reinforced to support rust-free aluminum grommets, that make installation of this tarp much easier.
While the tarp is initially strong enough to withstand heavy rains and strong winds, it does not seem to have received enough UV treatment to make it last more than 2 or 3 years. Cheap and simple, this polyethylene cover from Sunview looks nothing out of the standard but holds up very well in most greenhouse applications.
The polyethylene material is thin 6 millimeters but durable, allowing more sunlight to pass through and withstanding extreme weather conditions. It has been treated with an IR additive that helps reduce heat loss from inside the greenhouse and has also been treated with UV protection.
Keep in mind that polyethylene reacts slowly when put in contact with PVC. If your greenhouse has a PVC frame, make sure to treat it with primer before installing this plastic sheet. It will tear easily if the sheet gets snagged on some sharp object. The material is also capable of stretching by a small amount, which means that it can absorb sustained pressure without breaking.
Improper installation could result in the plastic sheet cracking prematurely due to UV damage. It can rip easily with rough handling, and you can easily punch holes through it with any moderately sharp object. On the upside, repairing a clear plastic film is easy.
Telling several brands of clear plastic films apart can be a daunting task, but this greenhouse film from Farm Plastic Supply can be distinguished on one thing: how clear the plastic is. Instead of the translucent and borderline-opaque appearance of many other plastic sheets, the almost-clear appearance of this greenhouse film should let in much more sunlight for your plants and crops.
According to Farm Plastic Supply, the UV treatment of this greenhouse film should help it last up to 4 or 5 years. It may be a very light material, but it can withstand strong winds and moderate snowfall.
Even if it does get damaged, one of the chief benefits of working with polyethylene is that it can be easily patched up. While outfitting a greenhouse with glass or fiberglass panels is the vastly preferred method for the durability and transparency that they offer, not everyone is willing to go through all the work and spend large amounts for that method. Plastic sheets offer a much cheaper and easier alternative — just drape them over your greenhouse frame and secure them at strategic points.
You can opt for the cheapest polyethylene sheets or splurge a bit for a polycarbonate panel that offers better longevity and rigidity. Amazingly, there are no comments.
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