2003 Volume 2 Issue 4 Pages 279-281
To determine the adequate pruning time during the rest year of satsuma mandarin trees in a systemized-alternate bearing orchard, the sprouting ratio and growth in new shoots were compared among satsuma trees (cv:‘Haraguchi Wase’) pruned in mid-February, trees pruned in mid-March (bud-breaking time), and trees that were not pruned. Pruning was performed for the whole tree canopy, and most of the 1-year-old branches were cut, then new shoots sprouting and growth on 2,3-year-old branches were compared with those of non-pruned trees. As for sprouting of spring shoots, pruning strongly increased it, and trees pruned in March produced over seven times more shoots than those that had not been pruned. As for sprouting of summer shoots, the remarkable occurrence was observed only in the trees pruned in March. The average length and leaf color of the new shoots (spring and summer shoots) did not differ between pruned and non-pruned trees. These results suggested that the bud-breaking stage is the most appropriate time for pruning satsuma mandarin trees during the rest year in a systemized-alternate bearing orchard. On comparison of carbohydrate (glucose, sucrose, and starch) and nitrogen (total nitrogen and NO3−) concentration in the bark of the 2 or 3 year-old branches, it was determined that pruning markedly decreased the starch concentration and slightly increased the soluble sugar concentration while the total nitrogen and NO3− concentrations increased before sprouting, depending on pruning time. These changes caused by pruning appeared to be a phase conversion to vegetative growth.
