Effects of irrigation interval and tillage systems on irrigated cotton and succeeding wheat crop under a heavy clay soil in the Sudan

A water crisis that occurs in Sudan during winter due to the competition for water to irrigate cotton (Gossipium barbadense L.) and wheat (Triticum aestivum L.) and to produce hydroelectric power necessitates a search for efficient means and ways of conserving water. Tillage is one of the methods for soil moisture conservation. Experiments were conducted in Gezira, Sudan on a Vertisol to determine if tillage practices and the lengthening of irrigation interval beyond two weeks during the period October–February would conserve irrigation water and maintain cotton yields. The residual effects of cotton tillage systems on the following wheat were also evaluated. The cotton experiment was conducted in split plot design with three replications. Three irrigation treatments of two-, three- and four-week intervals during the period October–February were used as main plots. Six tillage treatments were used as split plots (combinations of disc ploughing, cultivator and ridging). Treatments were compared by measuring cotton plant height and yields. Significant decreases in cotton yield were found between the four-week, and the two- and three-week irrigation intervals. However, no significant differences in cotton yields between the two- and the three-week irrigation intervals were detected. The lengthening of irrigation interval from two to three weeks during the period of irrigation water crisis (October–February) would result in conservation of about 3000 m³ ha^?1 of irrigation water. This corresponds to about 600 000 000 m³ of water for the cotton irrigated area in the Sudan. Therefore, the three-week irrigation interval during the period October–February has the potential for water conservation for cotton production in Gezira Vertisols, with the use of economical shallow tillage. The tested deep and shallow cotton tillage treatments did not have residual effects on the following wheat crop.