Improved spray deposition in full-leaf orchard spraying by sprayer type, nozzle type and air setting

To improve the current practice of spray application in pome fruit crops a research programme was setup assessing spray and liquid distribution of nowadays commonly used orchard sprayers. Improved spray deposition can lead to reduced use of agrochemicals and therefore reduced emission to the environment while maintaining high levels of spray drift reduction and biological efficacy Spray deposition and distribution in full-leaf apple trees was assessed for single row cross-flow fan sprayers (Munckhof, HSS), multiple-row sprayers (Munckhof, KWH) and a two-row tunnel sprayer (Lochmann). For the single and multiple row sprayers a distinction is made in the air delivery system; designed as a continuous slot and as spouts. Potential pathways of improvement identified are: (i) air amount, (ii) air distribution, and (iii) nozzle type, and therefore liquid distribution as the spray is transported by the moving air into the tree canopy. In a series of experiments, spray deposition measurements were carried out comparing the different sprayers and settings against a standard spray application, following the ISO-22522 protocol. Higher levels of spray deposition in tree canopy were observed with the use of 90% drift reducing venturi type nozzles, lower air assistance levels, multiple row spray applications, and its combinations. With optimised settings of the sprayer spray deposition at the leaves in the tree canopy at full leaf stage can be up to more than 50% higher compared to the standard settings of the sprayer in a similar situation. Overall results of the research are discussed, as well as how data may be presented following increased in-tree spray deposition. The results open the way to a classification system of sprayers with levels of improved spray deposition.