Water distribution analysis of a linear move irrigator by aerial survey and RTK-GNSS monitors

Irrigation uniformity in a semi-arid climate remains one of the main factors of water use efficiency (WUE) regardless of the level of agronomic advance, since over- and under-watered parts of the field represent wasted water or wasted yield at a given irrigation dose. The aim of this study was to analyze the underlying reasons for low WUE of linear move irrigators (LMI), detected by remotely sensed crop biomass maps in the Hula Valley, Israel. Head and tail towers were equipped with high-accuracy GNSS devices, recording their movements at 0.015 m accuracy. Periodic aerial surveys, run with multi-copter mounted visible and thermal cameras, showed stable and persistent over- and under-irrigation spatial patterns. Tower movement analysis revealed a “zigzag” pattern, where each tower lags behind and then catches up intermittently; over-irrigating during lags, under-irrigating during runs at the same spatial pattern over time, explaining the biomass variability. Deviations from the average at head and tail edge towers were in the 45–50% range of over-watering and the − 30% range of under-watering, and around ± 13%, at the mid part of the field. Yield sampling found 15% (pF > 0.069) yield loss. Sunken and winding wheel tracks observed in the field may have caused that movement pattern. Low WUE means waste of water that has a severe economic impact, especially in water scarce regions. Since water shortages are expected with climate change in many agricultural regions around the world, it is imperative to improve LMI machine movement uniformity, or to enable compensating irrigation control in order to solve water waste issues.