A severe plant water deficit imposed for nine days during the peak flowering period of cotton reduced yield more than stress periods of comparable length imposed either early or late in the flowering period. Water stress occurring early in the flowering period reduced yields by increasing shedding of squares before they flowered. Stress late in the flowering period reduced flowering rates and boll retention.

Research from which this report was prepared was supported in part by a grant from the California Planting Cotton Seed Distributors.