Articles
INFLUENCE OF GROWTH REGULATORS, RINGING AND ROOT CUTTING ON APPLE QUALITY AND PHYSIOLOGICAL DISORDERS
Trees treated every year with SADH considerably outyielded control trees.
The yield increase was smallest in trees treated from the plantation onward and greatest in trees treated from the third year after plantation.
Parallel to the yield increase the percentage of healthy fruit increased as well.
However, these fruits were smaller and therefore had less bitter pit.
Trees sprayed only every second year with SADH showed a marked alternation and yield was not increased as compared to control trees.
No yield increase could be achieved by treatments of the uppermost periphery of the trees as well.
The susceptibility to bitter pit of the fruits fluctuated from one year to another and was not exclusively determined by fruit size.
Similar fluctuations were found in fruit coloration.
Trees treated with SADH generally had more red coloured fruits.
While SADH-treatments had no effect on trunk circumference they reduced the weight of the prunings.
In a second trial the effect of root cutting and ringing was examined and compared with the effect of PP333 (Paclobutrazol) and SADH. The following apple cultivars were included: ‘Boskoop’, ‘Gravenstein’, ‘Golden Delicious’, ‘Glockenapfel’ and ‘Cox Orange’.
The root cutting reduced crop yield in all these cultivars except ‘Cox Orange’.
Ringing modified yield in very different ways.
The several treatments induced different effects on fruit size.
Ringing and SADH generally strongly diminished the mean individual fruit weight.
When ‘Gravenstein’ fruits of equal size were compared, those originating from trees treated with PP333 or from ringed trees showed a higher amount of bitter pit.
Taking all treatments into consideration, the susceptibility to bitter pit increased with increasing fruit size.
In all cultivars examined, fruit coloration was sometimes considerably improved by root cutting.
Ringing mainly intensified ground colour.
SADH-treatments strongly increased coloration in the cultivars ‘Cox Orange’ and ‘Gravenstein’. On the other hand, PP333 was inefficacious in this respect.