Yield Response to Variable Rate Irrigation in Corn

To investigate the impact of variable rate irrigation on corn yield, twenty plots of corn were laid out under a center pivot variable rate irrigation (VRI) system in an experimental field near Stoneville, Mississippi. The VRI system is equipped with five VRI zone control units, a global positioning system (GPS) receiver, and computer software. Each zone control unit controls the duty cycle of the sprinklers in the zone to realize variable rate water application across the pivot lateral. The GPS receiver determines the pivot position for identification of the control zone in real time. Supplemental irrigation was scheduled based on evapotranspiration (ET) estimates. A randomized complete block design was used in this study, with five irrigation rate treatments (0, 50%, 75%, 100%, and 125% of the rate determined using the Arkansas Irrigation Scheduler) and four replications. During the growing seasons in 2012 and 2013, VRI prescriptions were created based on the experimental design, and wirelessly uploaded to the system to apply varying amounts of water to each plot. The corn was machine harvested for yield. Results indicated that effect of irrigation rate on yield was not significant in 2012 and was significant in 2013. The treatment of 125% irrigation rate had the highest yield for both years. No significant yield difference between treatments in the 2012 season could be due to the sufficient rainfall in that summer. The ET estimates used in the irrigation scheduling might be lower than actual water demand of the corn crops for a higher yield.