Abstract
The present work analyses the traditional method of applying whitening products on Mediterranean greenhouses. Four commercial whitening products (agricultural solar protectors, ASPs), applied at four doses, were compared with a non-whitened cover. The traditional product “Blanco de España” with 99% calcium carbonate (CaCO3) and other three products with 97% CaCO3 that incorporate adhesives were tested. The use of adhesives in ASP did not influence the effect of the different products on the inside temperature, and at the same dose all four products show a similar behaviour. The findings support the maximum dose recommended by other authors of 0.50 kg L−1 (50/100), above which the transmissivity of the greenhouse cover decreases by over 50%. The effect of ASP on the transmissivity of the cover depends principally on the dose applied, but also on the climatic conditions (solar radiation, cloud cover, etc.) and on the time of year (solar elevation). The habitual use of a constant dose throughout the year does not seem to be the most adequate. Recommended doses should vary according to the time of year and the desired degree of transmissivity reduction. The adhesive components are shown to provide a high degree of protection against heavy rain. The study recommends a standardised method of ASP application, establishing a method that allows the grower to verify the concentration of the product that will remain on the greenhouse cover.
Highlights
The success of the greenhouses in the province of Almería (Spain) is founded on low-cost structures and a temperate climate that permit relatively high yields
Transmissivity data for ASPBE are compared to the other products, ASPF, ASPSF and ASPSP incorporating adhesives in Section 3.2 (Transmissivity of the cover with Agricultural Solar Protector with adhesives)
As occurs with ASPF, with the product ASPSF the results provide no clear indication that the adhesive clearly increases the effect of the product on the transmissivity of the greenhouse cover
Summary
The success of the greenhouses in the province of Almería (Spain) is founded on low-cost structures and a temperate climate that permit relatively high yields. At certain times of the year natural ventilation does not suffice to combat the high temperatures, and 99%. Of growers whiten the greenhouse cover [1]. To do so they apply a mixture of water and micronized calcium carbonate (“Blanco de España”). Despite the importance of this technique in the climate control of Mediterranean greenhouses, few technical or scientific works have studied this topic. Transmissivity of greenhouse cover is one of the main parameters influencing the energy balance that determine inside temperature, that can vary along a crop season between 0.44 and 0.80, depending on whitening [2]. Public Health 2019, 16, 958; doi:10.3390/ijerph16060958 www.mdpi.com/journal/ijerph
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