Maize growth and yield under daytime and nighttime solid-set sprinkler irrigation
Nighttime sprinkler irrigation usually results in lower wind drift and evaporation losses (WDELs) and better irrigation uniformity compared with daytime irrigation. However, daytime sprinkler irrigation modifies the microclimatic conditions within the crop canopy which could result in improved crop growth. We studied the effect of daytime and nighttime irrigation on the growth and yield of maize (Zea mays L.) irrigated with a solid-set sprinkler system. Two irrigation treatments were tested: daytime irrigation (starting at 1000 Greenwich Mean Time, GMT) and nighttime irrigation (starting at 2200 GMT). The same irrigation amount was applied in both treatments. The irrigation amount was determined as the difference between the crop evapotranspiration (ETc) and the effective precipitation. The WDELs of daytime irrigation were twice the nighttime irrigation WDELs. Daytime irrigation decreased the mean Christiansen coefficient of uniformity (CU) by 5 to 7% and the seasonal CU by 4%. Daytime irrigation caused a 10% reduction in maize grain yield, mostly due to a reduction in biomass production. The lower soil matric potential found with daytime irrigation late in the season indicated that a progressive water stress occurred that was due to less water availability and was caused by the higher WDEL for daytime irrigation. Even though positive microclimatic changes have been reported with daytime sprinkler irrigation, the results of our study indicate that they cannot compensate the negative effects caused for the crop by less water reaching the soil root zone because of increased WDEL and by poorer irrigation uniformity.