The experiment was carried out in Piracicaba, Brazil, in order to evaluate the effects of carbon dioxide, applied with the irrigation water, on the productivity and quality of the lettuce cultivated in plastic greenhouse. The treatments were designed in two plastic greenhouses, one was enriched with CO2 and the other without CO2, where lettuce variety Verônica was cultivated. The plastic greenhouse had eight plots with 1.2 x 6.0 m and spaced by 0.8 m. The crop was irrigated with "Rain Tape" drip with outflow of 1.15 L/h at operating pressure of 60 kPa. The irrigation was scheduled on a daily basis in order to apply 50 liters/m²/day of CO2 daily. The seedlings were produced in plastic greenhouse by using isopor tray with vermiculite as substratum. They were transplanted 30 days after sowing date in beds of 1.2 m width and 6.0 m length, with 0.30 m spaced between plants and 0,30 m between lines. After the application of CO2 (10/02/97 - 11/02/97) plants were harvested. Enrichment of irrigation water with CO2 increased the leaf area, dry weight of the aerial part by 27%, after 30 days of transplanting. The increase in lettuce head diameter, number of leaves and yield of heads was of 15.9%, 5.55% and 28.8%, respectively, in relation to the plot without CO2 application.
Lactuca sativa L.; plastic greenhouse; CO2; drip irrigation
