A comparison of three different cooling systems in parral type greenhouses in Almería

In warm climates, high temperature can limit growth and development of greenhouse crops and their product quality. Therefore greenhouse cooling has a high-priority to reduce these adverse effects. Together with natural ventilation, shade produced by whitewashing the greenhouse roof is the most usual cooling method in the whole of the Mediterranean area. However, this technique is not homogeneous; it is not selective and not adjustable. This inconvenience can be overcome by the use of other techniques such as shading with folding or rolling screens and/or evaporative cooling. This work evaluates three cooling techniques in parral greenhouses using a sweet pepper crop: whitening, shading with a mobile internal screen and cooling with a low pressure fog system. The latter gave the highest reduction in air temperature in the greenhouse in warm periods. However, final water consumption in the fog system was 319 mm, whereas irrigation water consumption was 520 mm. The evaporative cooling system, with 6.5 kg m-2 of marketable production and the use of interior shade screens (with 6.7 kg m-2), did not increase the yield obtained by means of traditional whitening (7.1 kg m-2) used by growers in the are