Abstract
1. Effects of severity (heavy, medium and light) of renovation pruning on improving the yield and the quality (size) of the nut in low-yield or senescent chestnut trees were examined.
2. Heavy pruning resulted in causing vigorous top growth, which was maintained for a longer period of time. Light pruning could increase tree vigour for only a short period of time, but its effect disappeared in the third year. In this case, however, the tree vigour was recovered by trying it again in the fourth and fifth year.
3. Removal of most of the primary or secondary scaffold branches stimulated the growth of shoots on the remaining scaffold branches in the same tree, as compared with that of a few of them.
4. The heavy pruning resulted in greater ‘leaf-area index’ and ‘leaf-area density’, and also much greater ‘leaf-wood’ and ‘leaf-sapwood’ ratios than the medium or light pruning.
5. The yield per tree was reduced by the pruning in the first year, but it increased markedly in propotion to the severity of pruning after the third year. Therefore, the cumulative yields per tree in five years were in the following order: heavy>medium>light pruning. Yearly changes of the yield per ground area occupied by a tree showed almost identical trends with those of the yield per tree.
6. Nut size increased with the severity of pruning. This effect did not disappear for five years in the heavily-pruned tree. Whereas, it disappeared in the third year in the lightly-pruned tree. In this case, the nut size increased again by another renovation prunings in the fourth and fifth year.
7. To improve the nut yield and quality in low-yield or senescent chestnut trees, therefore all their scaffold branches should be renovated at the same time or over the consecutive several years.
