Short communication. Performance of pneumatic spraying with an over-the-row sprayer in high density apple tree orchards

Abstract

In order to optimise an over-the-row pneumatic sprayer working in high-density apple tree orchards, tests have been conducted to study the deposition and distribution of its droplets. Field tests were conducted in an "artificial orchard" made with wooden posts and in an orchard of high density apple trees. To evaluate the quality of distribution, colored water droplets were collected on white plastic cards, which were then photographed. The effect of the angle between nozzle orientation and travel path on droplet deposition around wooden posts was studied. It was also studied the influence of air speed on the deposition on the apple trees and the drift and slide down of droplets. Tests show that the best nozzle position to get a uniform coverage around wooden posts which simulate tree trunks is face to face. This position also creates a tunnel of turbulence made by the wind without any physical wall. An air speed of 55 m sE–1 at the exit of the nozzles is the best to get uniform deposition of droplets in all areas of the trees. An smaller air speed of 41 m sE–1 gives a worse deposition on the back of the leaves, while a larger air speed of 63 m sE–1 gives a poor deposition on the outside leaves and can detach fruits when they are present on the trees.