Modelling the performance of air-assisted spraying on artichoke

Conventional treatments on horticultural crops present a great lack of efficiency in applications and difficult penetration into dense crops. Horticultural sprayers should be able to undertake applications in a wide range of conditions, depending on the kind of crop, the pest and its location. The aim of this work is to analyse the efficiency of an air-assisted sprayer on artichoke (Cynara scolymus L.), a horticultural crop whose density makes penetration of the plant canopy difficult. Tests of an oriented jet, air-assisted sprayer for vegetables, with flexible ducts that lead the air towards the crop, have been performed in the field, using different positions of air outlets, types of nozzle and volume rates. Droplet population and coverage at different parts of the plant have been measured by means of image analysis. Generalized linear models have been used to model the sprayer performances. Fan nozzles showed the best response to air assistance, achieving the highest deposits, especially in lowest leaves and on the undersides. The flexibility of air ducts allows the outlets to be adjusted as required and a variable number of them to be employed on every row, with a resulting variation in the airflow. Better coverage and uniformity were achieved by directing three outlets per row. Any decrease in deposits due to volume reduction was not proportional to the decrease in the applied volume and can be compensated with an adjustment of chemical doses. (C) 2002 Silsoe Research Institute. Published by Elsevier Science Ltd. All rights reserved.