Modeled crop water use and soil water drainage

• Published in: Agricultural water management 1991, Vol.19 (2), p.117-134
• Main Authors: Buller, Orlan, Manges, Harry L., Stone, Loyd R., Williams, Jeffery R.
• Format: Article
• Language: English
• Subjects: Agricultural and forest climatology and meteorology. Irrigation. Drainage; Agronomy. Soil science and plant productions; Biological and medical sciences; Earth sciences; Earth, ocean, space; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Hydrology. Hydrogeology; Irrigation. Drainage; Water resources
• ISSN: 0378-3774; 1873-2283
• DOI: 10.1016/0378-3774(91)90003-2

Soil water drainage is an integral aspect of the total water balance that needs to be recognized when irrigators seek to manage their system. Although irrigators in general realize that soil water drainage can and does occur, its significance or importance is not generally emphasized in educational programs. In this paper, a system of linked models describing the water balance and crop yield was used to select the most profitable combination of irrigation regime and crop type. The three models are a means of (1) estimating the crop water use, (2) a procedure to estimating crop yield in conjunction with a linear programming solution, and (3) the greatest value return to land, labor and water from irrigated crops. The water use model incorporates empirically derived soil water drainage equations to estimate drainage throughout the year on a silt loam soil in western Kansas for average rainfall. Soil water drainage increases as the soil water content increases in response to an increase in the water pumped. Results of this study show that little soil water drainage occurs with one 150 mm irrigation; however, most of the water pumped is lost to drainage after four 150 mm irrigations. Thus, the irrigator can control the amount of soil water drainage through the scheduling of irrigation. It is possible by proper selection of crops and irrigation regime to significantly reduce drainage without a proportional decrease in income. Educational programs to improve the management of water should include an emphasis on soil water drainage as well as crop water use. Managing water pumped to reduce drainage also reduces the potential of chemical loading of the aquifer from water soluble chemicals.