Why fruit trees need nitrogen fertilizer, application methods and precautions

In fruit tree cultivation, reasonable fertilization is a very important part, among which nitrogen fertilizer is indispensable. So why do fruit trees need nitrogen fertilizer? What are the application methods and precautions?

1. Why do fruit trees need nitrogen fertilizer?

Among the several types of major elements and trace elements required by fruit trees, only nitrogen fertilizer can promote the growth and development of fruit trees. This is because the nitrogen element is the main component of plant cell proteins, and is also a component of nucleic acids, chlorophyll, vitamins, enzymes and coenzyme systems, hormones, and many important metabolic organic compounds. Therefore, nitrogen can promote new shoot growth, increase leaf area, increase leaf thickness, increase the chlorophyll content in leaves, improve photosynthetic efficiency, favor trunk thickening growth and rapid canopy expansion, and promote early high yield. Proper nitrogen application can also promote flower bud formation, increase the fruit-setting rate, accelerate fruit enlargement, increase fruit yield, and improve fruit quality.

Therefore, generally during the vegetative growth of fruit trees, it is necessary to provide sufficient nitrogen element to fruit trees to meet their vegetative growth needs.

2. What are the methods and precautions for applying nitrogen fertilizer to fruit trees?

1. Nitrogen fertilizer application methods

(1) Application time: What is the best time to apply nitrogen fertilizer? In principle, it can be at any time during the growing season when you find that nitrogen is insufficient. However, to achieve the best fertilizer effect, it is often necessary to consider how the nitrogen demand of fruit trees changes with the seasons: that is, the early growing season requires a large amount of nitrogen for canopy development and fruit growth; in the late growing season, when fruit quality is forming, only a basic supply of nitrogen is needed. We believe there are two time periods that can be used for soil nitrogen application: the first is from bud break to the start of rapid new shoot growth; the second is the late growing season, when soil nitrogen fertilizer no longer affects fruit quality (before or just after fruit harvest).

(2) Application rate: How much nitrogen fertilizer should be applied? The answer to this question depends on three factors: the nitrogen demand of the fruit trees; the nitrogen naturally supplied by the soil; and the efficiency with which the fruit trees use the applied nitrogen fertilizer.

(3) Foliar nitrogen application: In addition to soil nitrogen application, foliar spraying of nitrogen can also help meet the nitrogen demand of fruit trees in the early growing season or improve the nitrogen reserves of fruit trees after autumn harvest.

If leaf testing in the previous year shows that the nitrogen content is lower than 2.2%, then applying foliar fertilizer in the early growing season helps fruit setting and early fruit growth. Foliar nitrogen fertilizer can extend the effective pollination time and promote cell division, but a lower concentration should be chosen to prevent burning the young leaves in the early growth stage. Generally, a 0.3% to 0.4% urea solution is used before flowering, and after flowering it can be increased to 0.6% to 0.7%.

Foliar nitrogen spraying in the late growing season can increase the nitrogen storage level of the tree body, thereby improving the plant's growth condition in the second year.

2. Precautions for nitrogen fertilizer application

(1) Neither excessive nor deficient nitrogen is suitable. Excessive nitrogen in the fruit tree body will cause an imbalance between carbohydrates and nitrogen in the tree body or disrupt the relationship with other elements, resulting in excessive vegetative growth, rampant growth of branches and leaves, poor flower bud differentiation, and severe flower and fruit drop.

(2) If fruit trees lack nitrogen nutrition, it will affect photosynthesis and protein formation. The spring shoot growth of the tree will be delayed, branches will grow thin and weak, leaves will be thin, small and pale in color, and the old leaves at the base of branches will age and turn yellow, causing early leaf drop in autumn and causing a large amount of fruit drop. When nitrogen is deficient, flowers are small, the fruit-setting rate is low, and the fruit is pale in color and poor in quality. Long-term nitrogen deficiency will reduce the stress resistance of fruit trees and shorten tree lifespan.

(3) Various nutrients should be kept balanced and coordinated. When fertilizing fruit trees, attention should be paid to maintaining the balance and coordination of various nutrients. Various nutrients have promoting and restricting effects on one another. For example, phosphorus deficiency can affect the metabolism of nitrogen-containing substances; potassium has a certain relationship with nitrogen absorption and protein synthesis. When applying nitrogen fertilizer, applying it together with phosphorus and potassium fertilizers gives good fertilization results.