OptiThin – Implementation of precision horticulture by tree-specific mechanical thinning

Abstract

Apples show biennial fluctuations in yields (alternate bearing). The alternate bearing cycle can be broken by reducing excessive flowers using either chemical or mechanical means. Currently, automatic thinning systems are treating the trees uniformly despite the fact that neighbouring trees can have a very different numbers of flowers resulting in different thinning requirements. In order to solve this problem the joint project OptiThin has been started. The aim of OptiThin was to develop a system that adapts thinning intensity individually to each tree by reducing the flowers efficiently and eco-friendly. In the result, OptiThin comprises a set of new technologies including: a) a stereo camera with software for real-time determination of flower density per tree; b) a shock absorbing camera platform; c) a mobile geographic information system; d) a decision support tool to calculated optimum thinning intensity based on current flower density and ancillary data (e.g. yield, soil); e) a mechanical thinning unit which is controlled in real-time. It was shown that adaptive management of excessive flowers could improve yield of marketable fruits and that environmental friendly mechanical thinning - without chemicals - is feasible.