Variable rate application of plant protection products in vineyard using ultrasonic sensors

The changes in the shape and size of vines during the growing season require a continuous adjustment of the applied dose to optimize spray application efficiency. Target detection with ultrasonic sensors can be used to adapt the applied dose following the principles of the variable rate technology. A multi-nozzle air-blast sprayer was fitted with three ultrasonic sensors and three electro-valves, to modify the flow rate from the nozzles in real time, in relation to the variability of crop width. A constant application rate of 300 l ha−1 was compared with a variable rate application using the tree row volume principle at a 0.095 l m−3 canopy. The total flow rate sprayed by the nozzles was modified according to the variations of crop width measured by the ultrasonic sensors. On average 58% less liquid was applied compared to the constant rate application, with similar deposition on leaves with both treatments. A detailed analysis of savings indicates differences between the lower, middle and top part of the crop, in accordance with the leaf area distribution with crop height. No significant differences between treatments were detected in uniformity of liquid distribution and capability to reach the inner parts of the crop. This important reduction in spray volume could be followed by an equivalent reduction of plant protection products but further research work is needed to guarantee biological efficacy of a reduced dose.