|Ayars, James - Jim|
Submitted to: Proceedings of the USCID Wetlands Seminar
Publication Type: Proceedings
Publication Acceptance Date: 6/1/2000
Publication Date: N/A
Citation: Interpretive Summary: Drainage is a fundamental requirement for irrigated agriculture in arid and semi-arid areas of the world. However, the disposal of drainage water from subsurface drainage systems can create an environmental problem when it contains salt and toxic trace elements. This is the case in the San Joaquin Valley of California where thousands of acres of productive agricultural land are threatened with water logging and salination due to the lack of adequate drainage water disposal facilities. The solution to the problem will entail improved irrigation management and managing subsurface drainage systems to reduce the total volume requiring disposal. This project evaluated the integrated management of an irrigation and drainage system to demonstrate methods to reduce drainage discharge by increasing crop use of shallow ground water. The project regulated the depth to the water table by restricting the outflow of the drainage and extended the irrigation interval. This resulted in fewer irrigations, more crop water use from shallow ground water, and reduced drainage. The yields were maintained and even improved with the changed management.
Technical Abstract: 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 occurred in the flood irrigated research plots.