Effects of Shading Using a Retractable Liquid Foam Technology on Greenhouse and Plant Microclimates

Abstract

<jats:p>Climate control is an important aspect of greenhouse crop management. Shading is one popular method for reducing excess solar heat radiation and high air temperatures in the greenhouse during the summer season. A new innovative technology has recently been developed and is based on the injection of liquid foam between the double layers of polyethylene of the greenhouse roof. The foam can be used as a shading method during the warm days of the summer. This is the first investigation into the effect of shading using the liquid foam technology on greenhouse and plant microclimates. Our research was conducted over 2 years in two different areas of Canada. Experimental greenhouses were retrofitted with the new technology. Tomato (<jats:italic>Solanum lycopersicum</jats:italic>) and sweet pepper (<jats:italic>Capsicum annuum</jats:italic>) were transplanted. Two shading strategies were used: 1) comparison of a conventional nonmovable shading curtain to the liquid foam shading system and application of liquid foam shading based only on outside global solar radiation; and 2) application of foam shading based on both outside global solar radiation and greenhouse air temperature. Data on the greenhouse microclimate (global solar radiation, air temperature, and relative humidity), the canopy microclimate (leaf and bottom fruit temperatures), and ventilation (opening/closing) were recorded. Our study showed that the retractable liquid foam technology improved greenhouse climate. Under some conditions (very sunny and hot days), a large difference in air temperature (up to 6 °C) was noted between the unshaded and shaded greenhouses as a result of liquid foam application (40% to 65% shading). Foam shading also increased relative humidity by 5% to 12%. Furthermore, bottom fruit temperatures stayed cooler 3 h after shading treatment was stopped. As well, a reduction in ventilation needs was observed with liquid foam shading.</jats:p>

Cucumber (Cucumis sativus) Transplants as Affected by Shade Level: Microenvironment, Growth, Photosynthetic Efficiency, Osmoprotectants, Plant Water Status, and Leaf Mineral Nutrients

“…A significant reduction in air temperature due to shading was also reported in a greenhouse study on strawberry, tomato, and sweet pepper even though a different type of shading was used compared to the current study [33,37]. Overall this study showed that vegetative growth characteristics i.e., leaves number, leaf area, shoot length, stem diameter, shoot FW, and shoot DW, increased when shade level increased (Table 1 & 2).…”

Uptake Efficiency of Phosphorus in Different Light Environments by Zinnia (Zinnia elegans) and Vinca (Catharanthus roseus)

“…Use of shade curtains or whitewash are common strategies to reduce plant and air temperature in greenhouses (Aldrich and Bartok, 1994). These approaches typically reduce temperatures by 1 to 4°C, depending on the conditions, but photosynthetic light is also reduced by 30% to 75% (Aberkani et al, 2010;Al-Arifi, 2006). The reduced radiation results in lower photosynthesis (Taiz and Zeiger, 1991), water use (Nobel, 1991), nutrient demand (Adams, 1980;Chapin et al, 1995), fewer or smaller flowers (Oh et al, 2009), and increases in height along with thinner leaves (Pramuk and Runkle, 2005;Stanton et al, 2010).…”

Compatibility between Crops and Solar Panels: An Overview from Shading Systems

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“…Aberkani et al [24] comment that differences in air temperature of up to 6 • C, a humidity increase of 10% and reduction in the need for ventilation are possible when polyethylene liquid foam is used in greenhouse ceilings.…”