Vulkan-Levy, R.
Ravina, I., Faculty of Agriculture Engineering, Technion, Israel Inst. of Technol., Haifa, Israel
Mantell, A., Institute of Soils and Water, The Volcani Center, ARO, Bet Dagan, Israel
Frenkel, H., Institute of Soils and Water, The Volcani Center, ARO, Bet Dagan, Israel

A field study was conducted in northwestern Negev to determine the effect of the amount of water and its salinity level on the yield of Pima cotton (cv. S5). Irrigations were applied by means of a double line-source sprinkler system using two parallel lines, each supplied with water of a different salinity. The water salinity ranged from 2 to 7.5 dS m-1 and the seasonal water application ranged from 30.0 to 68.0 cm. With water amounts of up to 50.0 cm (42% of Class A evaporation), an increase in water salinity caused a reduction in the seed cotton yield and the salinity threshold increased with an increasing amount of water. The maximum yield of seed cotton (about 5000 kg ha-1) was obtained with a water application of 50 cm and a water salinity between 4 to 5 dS m-1. With seasonal water applications exceeding 50 cm, an increase in salinity increased the yield. This is attributed to a depression of excessive vegetative growth in the presence of large amounts of water.