In the Delta States (Ark., La., and Miss.) annual rainfall should be sufficient to meet the water requirements of cotton. However, in many years the occurrence of some form of a drought has been common due to inadequate and poor distribution of rainfall (Musick and Hamill, 1984). Fifty-five percent of the 112,720 acres of irrigated cotton in the Delta counties of Mississippi (Northwest District) was sprinkler irrigated in 1983 (Thomas, 1984). This figure probably increased after the 1983 drought in Mississippi. The-popularity of sprinkler systems may have occurred due to the availability and convenience of overhead irrigation systems, high production costs, and the belief by farmers that supplemental irrigation represents a form of insurance against risk.

As the practice of sprinkler irrigation increases many questions with regard to cost, yield response, scheduling, quality, and other factors have been raised. Since 1952, a very large percentage of the published cotton irrigation research in the Delta States has been based on experiments operated under furrow irrigated conditions. Thus, researchers at the Delta Branch Experiment Station felt the need to expand its irrigation research with an overhead irrigation system under which several experiments could be handled per season. A lateral move overhead irrigation system was selected over a center pivot because it allowed experiments to be of a rectangular design to maximize land use. It was also felt that most of the information obtained from a lateral move system could be transferable to center pivot irrigation systems.