1, the best period of applying expansive fertilizer to early and middle ripe apples.

Because the growth and development of fruit can be divided into three periods, from fertilization to physiological fruit drop: the first growth stage. In the second and third growth stages, the volume of pulp cells and the transverse diameter of fruit increased rapidly. Therefore, it is the best time to apply swelling fertilizer to grasp the second and third growth stages of apples.

Then, the fruit trees and fruits of Apple Tengmu 1, Shanxia, Gala series and other varieties are in the stage of flower bud differentiation and fruit expansion from late June to early July, and a large amount of potassium and phosphorus fertilizers are needed for their growth and development. Therefore, the best time to apply expansive fertilizer is to choose 6 down and 7 up.

2. The best time to apply swelling fertilizer to late-maturing apples.

There are many varieties of late-maturing apples, and the best time to apply expansive fertilizer to Fuji apples is from late July to early August. This period of time has entered the end of the critical period of flower bud, and it needs more nutrition. Applying expansive fertilizer with potassium as the main fertilizer and phosphorus as the auxiliary fertilizer can regulate the growth of flower buds and accumulate sufficient nutrients. For fruit, it plays the role of prophase cell division and longitudinal growth, and cell division mainly depends on potassium and phosphorus to expand fertilizer, so the timing of expanding fertilizer is very important.

3. Spraying fertilizer on the leaves.

Foliar spraying of expansive fertilizer can be carried out alone or in combination with spraying. Be sure to spray evenly when cooking, especially on the back of leaves. Potassium dihydrogen phosphate has a good effect on promoting flower bud differentiation and fruit expansion. Amino acids and calcium fertilizers also have a good effect on preventing and treating Shui Xin, pockmarked seeds and bitter pox, improving resistance and increasing fruit hardness.

To sum up, spraying swelling fertilizer at the best time can play a key role in fruit swelling and flower bud differentiation, which is often said that "good steel is used on the blade".

Extended data:

1. After the spring shoots of apple fruit-setting fertilizer stop growing, the fruit begins to divide, and the number of cell divisions is directly related to the size and yield of fruit development. At this time, topdressing should be carried out to enhance leaf function, promote flower bud differentiation, improve fruit setting rate and promote fruit expansion.

2. The young fruit period of apple is a period of rapid division of fruit cells, and adequate nutrition is the guarantee to produce large fruit. At this time, the fruit consumes a lot of storage nutrients after flowering, leaf spreading, bamboo shoots and fruit growth. In addition to thinning flowers and fruits as early as possible, thinning over-dense and ineffective branches to reduce nutrient consumption, various nutrients should be supplemented in time as needed to promote the growth of new shoots and young fruits.

3. The development of apple fruit has entered a period of rapid expansion, which is the stage with the highest fertilizer requirement in the growing period. Fertilization is generally carried out before the fruit expansion period, in which nitrogen, phosphorus and potassium are the main fertilizers, which can improve the fruit hardness and sugar content and promote the fruit coloring.