Topdressing of apple trees in autumn should be reasonable.

The root system of apple tree is mainly distributed in the soil layer of 0 cm to 40 cm. There are two peaks in the root growth year, and autumn is the second growth peak. In autumn, it is necessary to fertilize apple trees reasonably. The fertilizer absorption characteristics of apple trees are as follows: nitrogen in the early stage, potassium in the middle and later stage, and the absorption of phosphorus is relatively stable throughout the year. Therefore, the following points should be paid attention to in fertilization:

1. According to the yield load to determine the amount of fertilizer, the proportion of fertilization should be balanced. The absorption ratio of nitrogen, phosphorus and potassium in apple was 1. 5. 5. Generally speaking, 0.8 kg of nitrogen, 0.4 kg of phosphorus and 0.8 kg of potassium are needed for every 100 kg of fruit.

two。 Autumn is the late growth stage of fruit trees, which should be dominated by potash fertilizer to promote fruit expansion and sugar accumulation and improve quality.

3. Seize the opportunity to apply fertilizer. In autumn, basal fertilizer is applied at the peak of root growth after fruit harvest, and it is best to apply base fertilizer after the growth of autumn shoots stops. In the north, it is from September to October.

4. Combined application of organic fertilizer, chemical fertilizer and extra-root fertilization. Organic fertilizer is generally used as base fertilizer, including cow and sheep manure and chicken manure. In terms of the total amount of fertilization, the amount of cow and sheep manure should be "jin fruit jin fertilizer", and chicken manure can be reduced by half. according to this total amount of fertilization in autumn, according to the deficiency of fertilization in spring, the amount of fertilizer and the type of fertilizer should be supplemented.

Pay attention to the location and depth of fertilization. In general, annular and semi-annular ditches are suitable for young trees. Strip ditch, hole application, radiation ditch fertilization and whole garden sprinkling method are mostly used for adult trees. The depth of fertilization is generally about 40 cm. With the expansion of the crown, the range and depth of fertilization should be increased accordingly, which should be applied in the main distribution layer of the root system.