Effects on root pruning of apple [Malus pumila] tree and its physiological change

Nine-year-old Fuji trees (M.26, M. prunifolia) and 13-tear-old Fuji trees (M.26, M. prunifolia), which were blown down by the strong winds of Typhoon 9119 in Kazuno Branch, Akita Fruit Tree Experiment Station in 1991, were used in this experiment. Changes in tree physiology and growth rate were absorbed after the typhoon. This experiment also included 16-year-old fuji trees (M.9) with mechanically pruned roots. Up to 60% of the total root volume was removed at the end of August and September. The author observed how fruit bearing and controlled fertilizer application affected the vigor recovery among the trees. The results are the following: 1) Shoot elongation and transpiration rates slowed down in trees where roots were pruned for less than 40%. However, no significant effect on yield was found. 2) Referring to the vigor recovery of trees blown down by the typhoon, the data suggest that trees which grew in deep soil have faster recovery than those in shallow soil. To regain the vigor of the typhoon-dama ged trees to the level of unpruned ones, it took one to two years for such where roots were 20% pruned. two to three years for those 40% pruned, and three to four years for those 60% pruned. 3) Shoot elongation and transpiration rate were considered as indices of tree vigor since significant effects were observed in response to the ratio of root pruning. 4) There was no significant difference in vigor recovery rate between trees where roots were mechanically pruned at the end of August and those at the end of September. 5) The data suggest that tree vigor recovery rate was slightly faster in the nonfruiting blocks. However the difference in tree vigor recovery rate was small when comparing blocks bearing 100% fruit load versus bearing 50% fruit load. 6) No correlation was found between the rate of tree vigor recovery and the amount of fertilizer application