ISHS Acta Horticulturae 903: IX International Symposium on Integrating Canopy, Rootstock and Environmental Physiology in Orchard Systems
EFFECT OF TIMING OF TOPPING TO REDUCE TREE HEIGHT ON SUBSEQUENT YEAR VIGOR OF EARLY-SEASON 'ARCTIC STAR' NECTARINE |
| Authors: | K.R. Day, R.S. Johnson, T.M. DeJong |
| Keywords: | Prunus persica, summer pruning, light management, mechanical topping, carbohydrate storage, size control |
| Abstract:
Production costs could be substantially reduced if the height of fruit trees could be lowered enough to eliminate the need for, or reliance upon, ladders in the orchard. Recent research demonstrates that high yields can be obtained on shorter trees with appropriate management techniques, but vigor control can be a problem. In 2004, selected rows of ‘Arctic Star’ nectarine trees growing in the Dinuba, CA area were topped in July, September and November. In July and September the plots chosen for topping were divided into two sub-treatments. One sub-treatment was topped to 3 m (down from approximately 5.5 m) and the other was topped at 3.7 m. In November, each of the 3.7 m July and September sub-treatments were re-topped to 3 m along with a block that was previously not topped. One treatment was also left untopped, and received normal dormant pruning during which height was reduced to ~4 m. All trees were hand pruned during dormancy to select fruiting wood, and pruning weights were recorded. Trunk and rootstock samples of wood tissue were taken from four trees of each treatment by using a 12 mm hole saw to extract a plug of wood from about 20 cm above the graft union and 10 cm below the graft union on December 1, 2004. Topping increased light penetration, and the July severe topping treatment stimulated regrowth that resulted in delayed bloom and fruit maturity in the following year. Contrary to our hypothesis, stored carbohydrates in the roots were greatest in the early topping treatments and lowest in the late topping events. Topping in September resulted in the lowest amount of summer pruning necessary in the subsequent year. | |
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