The work had the objectives of determining the effect of water table drawdown velocities on the growth and yield of lettuce crop in a flooded soil, identifying the stage of the crop cycle with the highest reduction in the productivity and obtaining a relation between the crop relative productivity and the daily stress index. The statistical experimental design was completely randomized in factorial scheme [(3 x 4) + 1], with three replications. The water table was lowered at 3 stages of the crop cycle (12, 22 and 32 days after the transplanting), four drawdown velocities (30 cm during 24, 48, 72 and 96 h) and a 13 treatment in which stress was not applied with the elevation of the water table. The lettuce presented as a sensible crop to the water-logging, although, it was not possible to define a value for the drainage coefficient because the highest drawdown velocity tested presented 50% of loss in the yield. Among the three crop stages in witch the stress caused by the water table elevation was applied, the first one caused the highest loss in the yield. The relative yield of lettuce plant had a negative linear relation with the daily stress index.
drainage; water-logging; water-stress
