TOMATO YIELD IN A CLOSED GREENHOUSE AND COMPARISON WITH SIMULATED YIELDS IN CLOSED AND CONVENTIONAL GREENHOUSES

In 2002 tomato was cultivated in a closed venlo-type greenhouse to investigate the influence of cooling with forced air movement along heat-exchangers combined with high CO₂ level under summer light conditions on production and quality. Transpiration in the closed greenhouse with forced air movement was, compared to a conventional greenhouse, higher at low light levels (2 instead of 1 kg/m²) and lower at high light levels kg/m² (4 instead of 5 kg.m²). Comparison of the observed yield with crop yields predicted with TOMSIM showed that yield was increased by 22% from 46.2 to 56.2 kg/m² compared to a conventional greenhouse with CO2 concentration always above 500 ppm. The higher CO₂ concentration in the closed greenhouse (always 1000 ppm) could explain only a 9% yield increase.