Synopsis: Cotton irrigations were adequately scheduled according to variations in the relative turgidity of the plant leaves sampled between 2:30 and 3:00 p.m. Cotton plants were able to endure short periods of severe plant moisture stress (66 to 62% relative turgidity) without significant yield reductions. Long periods of moderate to severe plant moisture stress (70 to 62% relative turgidity) during the bloom stage of plant growth caused significant yield reductions.