Reasonable autumn topdressing for apple trees, with scientific fertilization requiring careful attention

The root system of apple trees is mainly distributed in the 0-40 cm soil layer, and its root growth has two peaks during the year, with autumn being the second growth peak. Entering autumn, apple trees need reasonable topdressing. The fertilizer absorption characteristics of apple trees are: nitrogen is dominant in the early stage, potassium is dominant in the middle and late stages, and phosphorus absorption is relatively stable throughout the year. Therefore, fertilization should pay attention to the following points:

1. Determine the fertilizer amount according to the yield load, and the fertilization ratio should be balanced. The absorption ratio of nitrogen, phosphorus and potassium by apples is 1:0.5:1. Generally, every 100 kg of fruit produced requires 0.8 kg of nitrogen, 0.4 kg of phosphorus and 0.8 kg of potassium.

2. Autumn is the late stage of fruit tree growth, so potassium fertilizer should be the main type to promote fruit expansion and sugar accumulation and improve quality.

3. Grasp the timing of fertilization. In autumn, base fertilizer is generally applied after fruit harvest, when the root growth peak arrives. It is best applied after the autumn shoots stop growing, mostly from September to October in northern regions.

4. Combine organic fertilizer, chemical fertilizer and foliar fertilization. Organic fertilizer is generally used as base fertilizer; cattle and sheep manure and chicken manure are both acceptable. In terms of total fertilization amount, the amount of cattle and sheep manure should be "one jin of fertilizer per jin of fruit", and chicken manure can be halved. Autumn fertilization should be based on this total amount, and according to the deficiencies of spring fertilization, supplement the fertilization amount and fertilizer types.

Pay attention to the position and depth of fertilization. Generally, ring-shaped and semi-ring-shaped trench application is suitable for young trees. Strip trench, hole application, radial trench fertilization methods and whole-orchard broadcast application are mostly used for mature trees. The fertilization depth is generally about 40 cm. As the tree canopy expands, the fertilization range and depth should also increase accordingly, and it is best to apply fertilizer in the main distribution layer of the root system.