How to Control the Alternate Bearing of Plum Trees? Practical Cultivation and Management Methods

1. Reasonable pruning to regulate tree vigor. On-year trees should be pruned early (before the onset of winter) and heavily. Remove dead branches, residual branches, slender branches, scorched-tip branches, diseased and pest-infested branches, and excessively dense, crossing branches. Do more heading back to stimulate shoot growth; for vigorous branches and competing branches, cut back hard, removing 2/3 to 3/4 of the branch or leaving only 3 to 5 buds. Thin flower buds early, prune away excess flowering branches, and reduce the fruit load. Off-year trees should be pruned late (around the beginning of spring), keeping flowering branches and thinning out non-flowering vegetative branches. Leave branches unpruned or bend them down to moderate tree vigor, retain as many flowers and fruits as possible, and increase the fruit set.

2. Reasonable load to adjust the fruit set. On-year trees must have their fruit set controlled; fruit thinning should be done in late spring and early summer, that is, about 50 days after flowering. First remove diseased and pest-damaged fruits, deformed fruits, and fruits at the tips of shoots, then set the final fruit number according to a leaf-to-fruit ratio of roughly 18:1. Fruit can also be set according to branches: for large-fruited types, generally leave 1 fruit per spur, that is, leave 1 fruit per fruiting base branch about 10 cm long; for medium-fruited types, generally leave 1 fruit per spur and 2 fruits on strong branches, spaced 6 cm to 8 cm apart; for small-fruited types, leave 1 to 2 fruits per spur, spaced 4 cm to 5 cm apart. Thin fruits evenly throughout the tree to reduce the fruit load, promote the growth of branches and leaves, and ensure a good yield in the off-year. Off-year trees should have their plum fruit set rate increased; vigorous branches and strong shoots can be pinched or thinned to control shoot growth, and artificial pollination should be used in time, along with spraying 2,4-D and similar substances.

3. Scientific fertilization. On-year trees should be given heavy applications of fruit-swelling fertilizer and post-harvest fertilizer. After flowering, during the rapid fruit enlargement stage (about late May), apply per tree 50 kg of human and livestock manure, 0.3 kg to 0.4 kg of urea, and 0.3 kg to 0.4 kg of potassium sulfate to supplement nutrients and promote fruit development, shoot growth, and flower bud differentiation. After harvest, apply per tree 20 kg of decomposed organic fertilizer, 0.2 kg to 0.3 kg of urea, 0.4 kg to 0.6 kg of superphosphate, and 0.3 kg to 0.4 kg of potassium sulfate to replenish tree consumption, which helps restore tree vigor and flower bud differentiation, laying the foundation for a bumper harvest the following year. Off-year trees should be given a good pre-flowering fertilizer; about 10 days before flowering, apply per tree 0.1 kg to 0.2 kg of urea and 0.1 kg to 0.3 kg of potassium sulfate. In addition, during the flowering period, 0.1% to 0.2% borax or 0.2% to 4% urea can be sprayed to supplement the shortage of stored nutrients in the tree, improve tree nutrition, increase the fruit set rate, and raise the yield.