Irrigation management of cotton in the presence of a controlled drainage system

A three year project evaluating management of shallow saline ground water was conducted on four 30 acre plots located in the Tulare Lake Basin of California. Cotton was grown in a clay soil using flood irrigation, sprinkler irrigation, and a combination of sprinkler followed by flood irrigation. The water table was controlled to a depth of 4 feet below the soil surface at the outlet of the subsurface drain which was installed at a depth of approximately 5 feet below the soil surface. Irrigation scheduling used leaf water potential with the depth of application based on soil water content measured with a capacitance type soil water sensor. Yields were not negatively impacted in the managed area compared to the farmer's field. The ratio of yield to applied water was greater in the research plots in the controlled drainage area than in the farmer managed plots in the controlled area. Total water application was reduced in the test plots. Maximum potential ground water contribution to crop water use occurred in the flood irrigated research plots.