Submitted to: International Congress on Irrigation and Drainage
Publication Type: Proceedings
Publication Acceptance Date: 4/15/2005
Publication Date: 9/9/2005
Citation: Ayars, J.E., Schoneman, R.A. 2005. Irrigating field crops in the presence of saline ground water. International Congress on Irrigation and Drainage. Vol, 1-B, pp 131-133. Interpretive Summary: This paper describes an integrated irrigation and drainage water management system that was developed from a series of field research projects. The first project investigated using drip irrigation systems to apply saline drainage water as a supplemental irrigation water supply on a saline soil containing an operational subsurface drainage system. Results of this study demonstrated that saline water could be used in conjunction with good quality water to extend the available water supply and reduce the total drainage volume. Wheat yields were reduced as a result of using the saline water while the cotton and sugar beet yields were unaffected. Root zone salinity was effectively managed through winter rainfall and pre-plant irrigation. Boron accumulation in the soil profile was a problem after 5 years of operation. There was significant in-situ use of water by cotton in the furrow irrigated plots. The second project evaluated irrigation management of subsurface drip and furrow systems in tomato and cotton production in the presence of shallow ( 1- 2 m deep) saline (6-9 dS/m) ground water. This project demonstrated that cotton and tomato could use significant quantities of water from saline shallow ground water if the irrigation was properly managed. In one year cotton extracted approximately 40% of the 640 mm water requirement from shallow ground water. The results also demonstrated that salt in the root zone can be effectively managed through pre-plant sprinkler irrigation without the presence of a drainage system. Yields of both crops were increased with the use of subsurface drip irrigation. The third project evaluated the potential for managing the water table position using controls on the subsurface drainage laterals as a means to promote in-situ crop water use. Results demonstrated that the water table can be effectively managed without adverse effects on soil salinity or crop yield. In-situ use by the crop was increased as a result of the water table controls. The combined results of these projects demonstrated a water management system that incorporates the active management of both irrigation and subsurface drainage systems to maximize water use efficiency in irrigated agriculture.
Technical Abstract: Irrigating crops in the presence of saline ground water presents unique opportunities and challenges. As the world demand for water increases, it is incumbent on agriculture to maximize the use of water of all qualities. Traditional irrigation management in saline environments is designed to provide leaching of salt and the discharge of saline water in an uncontrolled fashion. This is no longer acceptable and management options were developed to maximize the use of water of all qualities and to reduce the subsurface drainage discharge to a minimum. This paper describes the integrated management of irrigation and drainage systems in saline environments that will increase in-situ crop water use of ground water and reduce drainage flow without reducing yields. The research demonstrated that when in-situ crop water use from ground water was included in the irrigation schedule, drainage flow and irrigation water requirements were reduced. Subsurface drip irrigation could be effectively used in areas without a subsurface drainage system without a loss in yields, and reduced deep percolation to the ground water. Salt in the root zone was effectively managed using pre-plant irrigation in areas with and without subsurface drains. Control structures installed on a subsurface drainage system made it possible to control the water table position and reduce drainage flow.