Variable Rate Precision Irrigation Technology for Deficit Irrigation of Processing Tomato

Abstract Centre pivot machines, with a variable rate irrigation (VRI) package that provides individual sprinkler control systems (VRI iS), are not common. This research focuses on how uniform the water distribution is under VRI control, and on the size of over‐ and under‐irrigated areas and volumes. Moreover, we wanted to know how wide transition zones are. We conducted different uniformity measurements using common rain gauges for measuring water application depths. Besides grid shape and radial direction measurements for uniformity, perpendicular measuring lines to borders were set to evaluate transition zones. In a processing tomato deficit irrigation experiment, we investigated how different plant properties react to different water depths. Results showed that very good uniformity is achievable both in the IR100 and IR50 application rates, but the former showed higher uniformity. CU C ranged from 91.8 to 92.9% and 88.8 to 90.8% in the IR100 and IR50 rates respectively. The highest RMSE was 2.65 mm. The amount of over‐ and under‐irrigation was not significant. Transition zones were not equally wide; 9 m was enough for transition widthways between the IR100 and IR50 rates, but was wider longitudinally. This technology is suitable for conducting deficit irrigation experiments, but consideration of transition zones is important at plant sampling. © 2018 John Wiley & Sons, Ltd.