Lettuce of Ahvaz (modified) with a scientific name Lactuca sativa varieties Romaine or Cos has one of the highest yields among the different types of country. In this study, the lettuce yield under different treatments was evaluated. The statistical method of this research is factorial design in a randomized complete blocks that major factor is irrigation frequency includes A1 and A2 (1 day and 2 days) and minor factor is irrigation regime that includes B1 and B2 (100% water requirement and 80%

more »

... of the crop water requirement).This experiment was performed in 4 replicates.For this research,4 chasis in the greenhouse is devoted that plays a rol of replicate.Each block consists of the 12 plants on a row crop that were irrigated by a drip irrigation lateral tape type.For irrigate the crops was used the drip irrigation with tape type, emitters spaced 20 cm diameter of 20 mm.Soil moisture was measured with TDR device.In this experiment, lettuce height was measured during the growing season and the relationship between plant height and number of days were presented with a high correlation. Also water use efficiency was measured. Results showed that irrigation frequency under greenhouse conditions did not cause significant difference on the water use efficiency. Reduction the amount of irrigation water caused that water use efficiency increased significantly. So that the best water use efficiency was happened in the treatment of 80% water requirement with irrigation frequency 2 days to the amount 25.02 kg/m³ and the minimum water use efficiency was happened in the treatment of 100% water requirement with irrigation frequency 1 days to the amount 16.89 kg/m³.