The use of water by cotton crops in Abyan, South Arabia.
Cotton was grown with 15, 45, 60 and 90 cm of irrigation water, applied before sowing. After irrigation there were 10, 28, 45 and 60 cm of available water in the uppermost 3 m of the profiles of plots receiving these rates. The estimated quantities of water used by the crops were 14, 34, 46 and 67 cm, respectively. On plots where the supply of water to the plants became limiting a decrease in vegetative growth was observed, followed after about 2 weeks by a decrease in the number of new fruiting points and an increase in the percentage of young flower buds shed. This was followed after another 2 weeks by the shedding of maturing bolls. To obtain most efficient use of water over the Abyan delta as a whole, irrigation rates would need to be adjusted to provide 50 cm of available water.-R.B.