Crop load regulation of fruit trees by means of a mechanical flower thinning device.

摘要

The aim of our study was to mechanically thin apple flowers without use of chemicals in orchard biosystems. The objectives were to remove, on average, one flower per cluster and concomitantly minimise any leaf damage, to improve fruit quality, to reduce hand thinning and overcome alternate bearing. The constructed device had three adjustable horizontal rotors with vertically rotating brushes. Apple trees grafted on M.9 rootstock were mechanically thinned at blooming with 300-420 rpm rotation and 5 or 7.5 km/h vehicle speed; adjacent untreated and manually thinned apple trees of the same rows served as controls. Mechanical thinning resulted in better fruit quality viz increased soluble solids (taste), acidity, fruit size, fruit with advanced ripeness, and additionally better red fruit colouration, associated with a higher (healthy) anthocyanin and chlorophyll content. The best engineering results were obtained with 360 rpm with both 5 km/h and 7.5 km/h vehicle speeds, a compromise between minimal tree damage and sufficiently reduced fruit crop of good quality including colour and taste as well as fruit size.