Effect of full and limited irrigation amount and frequency on subsurface drip-irrigated maize evapotranspiration, yield, water use efficiency and yield response factors

The objectives of this study were to: (1) to evaluate the effects of subsurface drip irrigation amount and frequency on maize production and water use efficiency, (2) develop production functions and quantify water use efficiency, and (3) develop and analyze crop yield response factors (Ky) for field maize (Zea mays L.). Five irrigation treatments were imposed: fully irrigated treatment (FIT), 25 % FIT, 50 % FIT, 75 % FIT, rainfed and an over-irrigation treatment (125 % FIT). There was no significant (P > 0.05) difference between irrigation frequencies regarding the maximum grain yield; however, at lower deficit irrigation regime, medium irrigation frequency resulted in lower grain yield. There was a decrease in grain yield with the 125 % FIT as compared to the FIT, which had statistically similar yield as 75 % FIT. Irrigation rate significantly impacted grain yield in 2005, 2006 and 2007, while irrigation frequency was only significant during the 2005 and 2006 growing seasons (two dry years) and the interacting effect was only significant in the driest year of 2005 (P = 0.006). For the pooled data from 2005 to 2008, irrigation rate was significant (P = 0.001) and irrigation frequency was also significant (P = 0.015), but their interaction was not significant (P = 0.207). Overall, there were no significant differences between irrigation frequencies in terms of grain yield. Ky had interannual variation and average seasonal Ky values were 1.65, 0.91, 0.91 and 0.83 in 2005, 2006, 2007 and 2008, respectively, and the pooled data (2005-2008) Ky value were 1.14.