REGULATION OF GROWTH AND CROPPING OF APPLE TREES BY CULTURAL PRACTICES AND CHEMICAL MEANS
In the experiments mainly the cultivars 'Boskoop', 'Cox's Orange Pippin', and 'Golden Delicious' were used.
Nitrogen fertilization and time of nitrogen application gave little control of shoot growth. Even O nitrogen for a period of 12 years decreased total growth by only 5 percent, compared to 100 or 200 kg nitrogen per ha.
The mode and time of pruning gave more pronounced results. If the trees were not pruned at all for 3 successive years, shoot growth decreased rapidly and profoundedly. Comparable results were obtained, when pruning was done only in August, and not in winter. Flowering of vigorous mature trees in these treatments was the more improved, the better shoot growth could be controlled. But biennial bearing of the trees could not be prevented by these cultural methods. Chemical fruit thinning made the trees crop more evenly. Even more regular crops were achieved by an additional application of SADH + CEPA 2 weeks after fruit thinning. But this treatment sometimes gave harmful fruit drop, retarded fruit growth and worse fruit storage quality.