RHEA airblast sprayer: calibration indexes of the airjet vector related to canopy and foliage characteristics.

The 2009/128/EC directive requires new management techniques of the pest control practices. In this respect, research is moving towards the definition of new solutions to optimize the pesticides use. In accordance with the European general guidelines, in the RHEA Project (Robot Fleets for Highly Effective Agriculture and Forestry Management NMP-CP-IP 245986-2 RHEA) the U.O. of Florence has developed a sprayer prototype that can vary the air flow rate and the spray mixture. This meets the purpose of spraying optimization because, the right practice, should include an adjustment of the variables of spraying in relation to the target features (Chen. This study was focused on the air flow management. In the Rhea air blast sprayer, to manage this variable a system made of butterfly valves located on the main inlet manifold and in the fan calotte collector, were designed. However, to fulfill this purpose, it is required the air flow characterization and its calibration. In this connection, a sensor that provides data related to the aerodynamic force that the air vector produces on an surface area, was developed. Furthermore, an instrumental procedure to measure the instantaneous force of the air flow produced by the fan and diffusers of the sprayer, was developed. The assessment involves the quantification of air jet momentum at a defined point at the outlet of the sprayer. Moreover, it seems possible to use the effect produced by the air jet momentum as measured by the reaction force on a standard surface during the time of sprayer passage. The integral of collected data, in the different infinitesimal times, during the treatments, can be assumed to be equivalent to the impulse of the air flow jet on the surface unit on the leaves. An apparatus that allows to measure the impulse and thus to estimate the air flow momentum in dynamic conditions (i.e., with sprayer moving in the orchard) and at different distances, with or without canopy interference, was built. Laboratory and field tests with a sprayer to validate the procedure were performed. Results showed a new possibility to compare sprayer features and operative parameters with the index impulse assessments. This permits the definition of the most appropriate set-up parameters to obtain an efficient spray application in different crop conditions.