Maize response to different subsurface drip irrigation management strategies: Yield, production functions, basal and crop evapotranspiration

Grain yield, irrigation-yield production functions (IYPFs), evapotranspiration-yield production functions (ETYPFs), total soil water-yield production function (TSWYPF), crop evapotranspiration (ETc), and basal ET (ETb) response of subsurface drip-irrigated (SDI) maize were investigated under full irrigation treatment (FIT), 75 % FIT, 50 % FIT, and rainfed (RF). Yield response to irrigation differed significantly (P<0.05) between the treatments with FIT having the highest grain yield, followed by 75 % FIT, 50 % FIT, and RF in all growing seasons. There was a 14, 6, and 12 % yield reduction in 75 % FIT, 50 % FIT, and RF with respect to FIT, respectively. FIT had the highest ETc, followed by 75 % FIT, 50 % FIT, and RF. ETc reduction with 75 % FIT, 50 % FIT and RF with respect to FIT had similar reductions between the years. Under these experimental conditions, ETc of SDI-irrigated maize can be expected to be reduced by 5.2 % (25 mm), 13 % (65 mm), and 26 % (130 mm) with the limited irrigation (75 % FIT and 50 % FIT) and RF, respectively. The amount of irrigation water required for maximum grain yield varied between the growing seasons as a function of climatic conditions (262, 225, and 173 mm in 2004, 2005, and 2006, respectively). Based on the IYPFs, a 25.4 mm of irrigation application resulted in 0.061, 0.063, and 0.066 t/ha yield increase (beyond the intercept) in 2004, 2005, and 2006, respectively, with a 3-yr average of 0.063 t/ha. A 25.4 mm of irrigation application resulted in 15.6, 16.0, and 13.7 mm of increase in ETc (beyond the intercept) in 2004, 2005, and 2006 seasons, respectively, with a 3-yr average of 15.1 mm. On a three-year average basis, 10.7, 29.1, and 67 % yield reduction in 75 % FIT, 50 % FIT, and RF treatments with respect to FIT can be expected under these climate, soil-water, and crop management conditions with SDI-irrigated maize. A strong dependence of the ETYPF slopes on RF treatment’s yield was observed. ETb had substantial inter-annual variation as 356, 230, and 315 mm in 2004, 2005, and 2006, respectively. ETb was strongly and positively correlated (R2=0.99) with the seasonal precipitation and strongly, but negatively correlated (R2=0.89) with seasonal cumulative thermal unit (Growing Degree Days). Based on the pooled ETYPFs, a 25.4 mm of ETc resulted in 1.86, 1.72, and 2.61 t/ha grain yield (beyond the intercept) in 2004, 2005, and 2006, respectively, with a seasonal average of 2.1 t/ha. Data and information of this research can provide guidance for irrigation professionals, managers, advisors, engineers, agronomists, economists, and other professionals and can be incorporated into the planning, forecasting, allocating and managing of water resources availability-demand-actual use analyses and decisions to enhance crop production efficiency.