COMPARISON BETWEEN GREENHOUSE TYPE, AND THEIR EFFECTS ON TWO LETTUCE CULTIVARS YIELD, AND BOTRYTIS INCIDENCE

An experiment was carried out in Trás-os-Montes region, North of Portugal, to test the effect of greenhouse type and its restricted ventilation, on greenhouse climate, lettuce yield and on grey mold control.
A single tunnel and a double-span, round arched, plastic greenhouse were used.

Climatic variables such as air temperature and air relative humidity were measured inside greenhouses and outside.
In spite of the different ventilation possibilities, the ratio ventilation area to greenhouse area, was kept the same on both greenhouses, as well as the opening and closing time of the windows.
Growing techniques were identical.

No chemicals were sprayed for Botrytis control.
Any attacked plants were recorded.

Results showed significant differences between greenhouse type and cultivars.
A better yield was achieved in the tunnel greenhouse, with less commercial production losses, and a large ratio of total weight to clean weight, probably due to the poorer ventilation rate of the double-span greenhouse.