At the end of every pesticide application the sprayer results contaminated either internally – in the tank and in the hydraulic circuit - or on its external surfaces with a fraction of spray mixture applied in the field. If not adequately managed, these chemical residues may cause negative effects on the environment.
The amount of spray mixture residue in the tank at the end of treatment depends partly on the technical features of the sprayer (fraction not suckable by the pump) and partly on how the sprayer has been adjusted in order to use up the whole pesticide tank content on the sprayed area. Quantity and pesticide concentration of the leftovers are also influenced by the tank capacity and shape as well as by the efficiency of the agitation system. In order to minimise the amount of residues present in the internal parts of the sprayer at the end of the application it is always recommendable to use ENAMA/ENTAM certified sprayers, which fulfil the technical requirements of the International Standards in terms of maximum residuals and efficiency of the tank agitation system. Moreover, when the tank content is going to be finished, it is important to close the backflow line, so to allow the pump to suck as much as possible all the spray mixture present in the sprayer.
Concerning external contamination of sprayers, its amount depends on the sprayers features (e.g. the presence of a fan enhances a lot the external contamination of the machine), on the spray quality (higher contamination applying fine droplets), on the air flow parameters adopted and on the characteristics of the product sprayed (some formulations are more sticky and persistent on the machine).
Management of sprayer cleaning directly in the field allows to simplify the disposal of the effluents at the farm, reducing their amount and concentration. It is therefore necessary to use the rinse water tanks of adequate capacity equipped with efficient systems for internal and external cleaning.