Role of Transpiration Reduction during Center-Pivot Sprinkler Irrigation in Application Efficiency

The magnitude and duration of corn transpiration reduction during center-pivot sprinkler irrigation was analyzed on a commercial plot. The irrigation event was defined as the period during which the pivot arm was passing over the transect AC and water droplets were moistening the plants (moist treatment). Corn transpiration rates were measured at three spots of that transect and simultaneously at another spot (dry treatment) located approximately 270 m east from the transect AC. Corn transpiration rates for the moist treatment location were reduced by 30-36% compared to the dry treatment location during the irrigation event. After irrigation, the transpiration reduction lasted for 1.8-2.6 h, and ranged from 22-29%. The gross wind drift and evaporation losses ranged from 10-13% of the applied water, whereas the net interception losses were 2% of the applied water. Considering the observed corn transpiration reduction during and after the irrigation, the net sprinkler evaporation losses ranged from 11-13% of the applied water, with no relevant differences along the pivot arm. DOI: 10.1061/(ASCE)IR.1943-4774.0000532. (C) 2013 American Society of Civil Engineers.