Spray interactions with a windbreak netting used in orchard applications

Abstract

An extruded plastic windbreak netting, with an optical porosity of 64%, was used to evaluate its potential in reducing sprayer air velocity and intercepting spray droplets in simulated orchard applications. The air velocity reduction was assessed in laboratory tests carried out under static and dynamic conditions. In field tests, the netting was directly sprayed with two orchard airblast sprayers, equipped with different nozzle types.Air velocity reduction was higher in the dynamic setting but decreased at lower air velocities. It also decreased when the netting distance from the air outlet increased. In field tests, the analysis of spray fallout depositions in open area conditions revealed lower recovery rate for conventional than air induction hollow cone nozzles. Comparing the fallout collected on sampling lines (perpendicular to the sprayer travel path) behind the netting and in the open area showed an average spray retention of 30.5% for the netting. The netting affected the fallout pattern along the sampling line, showing a droplet trajectory deflection associated with the momentum and kinetic energy losses. An increase of ground deposition was noticed just behind the netting (up to 2 m). At farther distances ground deposits decreased considerably. The results showed the potential for using a windbreak netting to simulate the droplet retention characteristics of a hypothetical tree foliage, in order to reduce the effect of canopy variability in certain orchard applications studies.