The impact of apple tree training system on spray deposit coverage values within the tree crown | Vpliv gojitvene oblike jablan na stopnjo pokrovnosti obloge skropilne brozge v razlicnih sektorjih krosnje dreves

The impact of apple tree training system on spray deposit formation within the tree crown was studied in the apple tree plantations with super-spindle (SS), modified slender-spindle (MSS), slender-spindle in a twin row (SSTR) or V-system super-spindle (VSS) training systems. The formation of spray deposit within twelve crown positions was evaluated by measurements of spray coverage values obtained on water sensitive papers (WSP; % coverage) and measured by Optomax image analyser. At all plantations, sprays were applied by the same standard axial fan sprayer equipped with three types of nozzles (Lechler TR, Lechler ID90 or Lechler ID120) and calibrated to deliver 350 or 700 litre of spray per hectare. The tree training system had a significant impact on the uniformity of spray coverage values detected in the twelve different crown regions and also on the absolute spray coverage values measured. The interactive effects of nozzle type, spray volume and type of tree training system on spray coverage were observed. By increasing the spray volume from 350 to 700 l/ha the spray coverage was increased significantly in all plantations. The increase was the least in the SS tree training system (30 %) and the highest in the MSS trained trees (48 %). The influence of nozzle type on achieved coverage values was significant but not the same far all the studied tree trainings systems. In case of SS trees, the highest coverage (average of twelve crown positions) was achieved by ID120 nozzle (40,3 %), in MSS trees by ID90 (26,3 %), in SSTR trees when using ID90 nozzle (24,6 %) and in VSS trained trees by ID90 nozzle (30,3 %). Drift-reducing nozzles of ID type provided higher coverage values than standard TR nozzles in all four types of plantations in at least half of the observed crown positions. The highest variability of coverage values among 12 crown positions was observed in SSTR trees and the smallest in SS trees. The coverage values measured in SSTR, VSS and MSS trees were significantly lower than in case of SS trees. It can be assumed, that spraying tress of SSTR, VSS and MSS training systems by the same sprayer whose nozzle configuration and operating parameters are adapted to the SS trees, can not provide spray coverage high enough for sufficient disease and pest control. The nozzle type, nozzle configuration and operating parameters of sprayer therefore must be adapted to the specific tree training systems.