An experiment was carried out from June 8th to July 24th, 1998, in the Departamento de Fitotecnia, ESAM, Brazil, to evaluate the performance of three lettuce cultivars in six different planting spacings on lettuce leaf yield under high temperature and ample sunlight. The experimental design was a randomized complete block in a 3 x 6 + 1(additional treatment) factorial scheme, with four replications. The treatments were the combination of three lettuce cultivars (Great Lakes, Elisa and Babá de Verão) and six planting spacings (20 x 20 cm, 20 x 25 cm, 20 x 30 cm, 25 x 25 cm, 25 x 30 cm and 30 x 30 cm) plus one additional treatment (Great Lakes in the 20 x 20 cm spacing under shading throughout the crop cycle). Evaluations were performed for plant height and diameter, leaf number per plant, shoot dry matter content, leaf yield, gross and net incomes, and rate of return. The cultivar Great Lakes had the greatest leaf yield and economic indices. The best spacing regarding leaf yield, shoot dry matter content, and economic indices was 20 x 20 cm. Leaf number per plant was higher in the cultivar Elisa but was not affected by spacings.
Lactuca sativa L.; shading; leaf yield
