Abstract
The purpose of this study was to identify the effects of using aluminised screens offering different degrees of shading on the production and quality of tomato cv Atlético crops grown under greenhouse conditions. The study was performed in an Almería-type "raspa and amagado" commercial greenhouse with an area of 10,000 square m. The covering material was heat-insulating polyethylene (200 microm thick). The passive ventilation area of the greenhouse was 14%. Transplantation of the plantlets into the sandy mulch soil of the greenhouse was performed to leave a density of 1.78 plants/square m. Plants were grown under extendable aluminised screens offering 40% (T40), 50% (T50) and 60% (T60) shading, as well as under traditional whitewashing conditions (control). The screens were used during the middle hours of the day in summer with a view to reducing radiation, and at night in autumn and winter to prevent the loss of heat via outgoing long-wave infrared radiation. Only the T60 treatment returned significantly different results compared to the control: the T60 fruit had a lower deg Brix but were firmer in both growing seasons.
Highlights
In the horticultural production systems of southeastern Spain, the high temperatures and changing air moisture levels prominent during the first (July, August and September) and the last (May and June) months of cultivation are far from optimal. This causes stress in those crops whose production cycles coincide with these periods, and production is reduced because of setting and fruiting problems
The application of a solution of whitewash and water to the greenhouse covering is a widespread practice in southeastern Spain, the aim of which is to reflect some the solar radiation that would otherwise reach the plants; the energy reflected by the whitewash does not accumulate inside the greenhouse
The mean temperature (Table 1) and relative humidity (RH) (Table 2) for both seasons were higher inside the greenhouse than
Summary
In the horticultural production systems of southeastern Spain, the high temperatures and changing air moisture levels prominent during the first (July, August and September) and the last (May and June) months of cultivation are far from optimal. The application of a solution of whitewash and water (known as “Spanish White”) to the greenhouse covering is a widespread practice in southeastern Spain, the aim of which is to reflect some the solar radiation that would otherwise reach the plants; the energy reflected by the whitewash does not accumulate inside the greenhouse. Under such conditions transmissivity levels are around 30% of the overall exterior radiation (Morales et al, 1998). Detergents can be used to help remove unwanted whitewash (FernándezRodríguez et al, 1999), but these can corrode the wires mesh used to hold the plastic sheeting in place
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