Detailed Explanation of the "Three Early" Cultivation Techniques for Plums

"Three Early" cultivation techniques for plums:

1. Reasonable pruning to promote early flower bud formation: In the year the plum is planted, when the new shoots grow to about 30 cm, pinch off the growing tips to control growth, stimulate secondary shoots and form flower buds. For example, on Misi plum, Oishinaka, and Oishiwase, after pinching, 40% of the secondary shoots can form flower buds, while plum trees not pinched in summer generally do not form flower buds that year. During winter pruning in the first year, current-year branches are generally left unpruned and laid flat, while densely crowded branches, water sprouts and shade-casting branches are removed by thinning. In this way, a large number of clustered flower buds can form on the laid-flat branches of that year. During winter pruning in the third year, the branches that were laid flat are appropriately retracted to prevent the tree from weakening. In subsequent years' winter pruning, the same pruning sequence is used.

2. Reasonable fertilization to promote flower bud differentiation and early ripening and coloring of fruit: Fertilization should pay attention to the combination of various fertilizers, especially applying sufficient organic fertilizer before leaf fall in autumn. Before the plum fruit ripens in the second year, an appropriate amount of phosphorus and potassium fertilizer should be applied to promote flower bud differentiation and fruit coloring. Nitrogen fertilizer has a relatively large effect on how early or late plum fruit matures, so before plum harvest, the amount of nitrogen fertilizer applied should be controlled. In this way, the plum fruit maturity period can be advanced, thereby increasing its commercial value.

3. Preventing low temperatures in spring to increase fruit set rate: Plums are often damaged by low temperatures during the flowering period, which affects fruit set. For this reason, irrigation can be carried out before buds sprout in spring to lower soil temperature, delay budbreak, and postpone the flowering period. In summer pruning, more pinching and heading back should be done to stimulate secondary shoots, using the characteristic that secondary shoots flower 7 to 10 days later than main shoots to delay flowering. In mid-to-late September in autumn, 100 mg of ethephon can be sprayed per tree, which can also delay the flowering period of the following year by 3 to 5 days. Using the above measures, damage to flowers from low temperatures in early spring can be avoided, thereby increasing the fruit set rate.