Effects of combined pruning treatments on fruit quality and biennial bearing of 'Elstar' apple (Malus domestica Borkh.)

The effect of four combined pruning treatments on yield, fruit weight (season 2003 and 2004), soluble solids content (SSC), total acid (TA), SSC/TA ratio and mineral content of 'Elstar' apples after storage for 16 weeks in air (season 2004) were studied. These treatments included canopy pruning with root pruning and trunk girdling, canopy pruning with root pruning, canopy pruning with trunk girdling, and solely canopy pruning. Root and canopy pruning with or without trunk girdling resulted in higher yield but did not affect fruit weight. Treatments with root pruning caused the lowest biennial bearing. Fruits of the trees, which were treated only with canopy pruning, had the highest N content. Fruits of the canopy and root pruned trees, with or without trunk girdling, had lower contents of the fruit P. Fruits of the trees, which were treated with canopy pruning and trunk girdling, had the highest total Ca content. Fruit water-soluble magnesium (WS Mg) was significantly different among treatments. Zn content was lower in trunk girdled and root pruned trees. Fruits of the trunk girdled trees had higher manganese contents. Fruits of the trees, which were treated only with canopy pruning, had significantly highest Cu content. Results show that root pruning combined with canopy pruning is effective method for reducing biennial bearing in 'Elstar' apple. Besides application in conventional fruit production, it is also applicable for organically produced fruits since it does not include use of growth regulators, or any other chemical compounds. Root pruning combined with canopy pruning can significantly increase tree productivity. Besides, this combined pruning treatment can stabilize yield without a negative effect on fruit quality. This practice can be safely recommended without a risk of negative effect on fruit quality.