Submitted to: Irrigation Association Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/16/2003
Publication Date: 9/16/2003
Citation: Wanjura, D.F., Upchurch, D.R. 2003. Irrigation strategies for optimizing yield and water use efficiency. Irrigation Association Conference Proceedings. Interpretive Summary: The demand for water is increasing and there is a continuing need to use water more efficiently. For crop production yield and water use efficiency change in opposite directions with amount of water used. There is a need to define yield and water use efficiency relationships to determine the optimum combination of yield level and efficient use of water to obtain economical production. A one year field study compared two strategies for cotton irrigation timing. One strategy maintained constant crop water stress (CS) levels during the irrigation season and the other strategy varied irrigation levels in proportion to the sensitivity of yield to water stress during different growth stages (VS). Lint yield increased in a positive curvilinear manner with irrigation and total water in both irrigation strategies. Total water applications of 57% of PET in the CS strategy and 53% of PET in the VS strategy produced the best combination of high yield and water use efficiency. Water use efficiency based on total water, greater than 44% in the CS strategy and 30% in the VS stratgegy had a common negative linear relationship with quantity of water.
Technical Abstract: Subsurface drip irrigation (SDI) can apply precise quantities of water uniformly along the row and enhance the efficiency of water use. The Biologically Identified Optimal Temperature Interactive Console (BIOTIC) irrigation timing protocol was used to control irrigation timing using two strategies for establishing different water levels in a cotton SDI study in 2002. Daily irrigation decisions for treatments in both strategies were determined by different time threshold (TT) values required to generate irrigation signals. The TT were specific accumulations of stress time which were periods when canopy temperature exceeded 28%C during the daytime. One strategy maintained different constant rates of irrigation (CTT) and a second strategy varied irrigation (VTT) during four growth stages in proportion to each stage's yield sensitivity to water stress. The purpose of the study was to compare the yield and water use efficiency (WUE) of the two irrigation strategies. Three water levels were established with each strategy. Cummulative irrigations in the CTT strategy were 398, 313, and 201 mm for the 2.5 hr TT, 5.5 hr TT, and 7.5 hr TT treatments, respectively. The VTT strategy had cumulative irrigations of 152, 262, and 318 mm for the LW, MW, and HW treatments. Lint yield increased with irrigation and total water for both irrigation strategies in a positive curvilinear manner. The 5.5 hr TT treatment in the CTT strategy and the MW treatment in the VTT strategy produced the best combination of high yield and high WUE. Irrigation and total water WUE values from both irrigation strategies had a common negative linear relationship with applied water, except for the 7.5 hr TT treatment which had lower WUE values. The performance of the CTT or VTT strategies in scheduling irrigation was inconsistent across water levels based on the criteria of yield and irrigation WUE.