The indispensable part of the growth process of fruit trees is the supply of fertilizers, especially in the annual growth cycle (before germination to leaves), the amount of fertilizer required is relatively large, then when does the fruit tree have a good topdressing effect? When is the best time to fertilize fruit trees?
1. Fertilization before germination
Inorganic nitrogen fertilizer should be applied mainly in the soil, and the application amount is about 1/3 of the annual nitrogen fertilizer amount. The purpose is to prevent the germination to the flowering stage, and the quality of the flower is poor due to nitrogen deficiency, resulting in serious falling flowers and fruits And poor growth of young leaves.
The nitrogen content in flower organs is the highest in all organs of the tree body. Taking apple trees as an example, the nitrogen content of flowers can reach about 5%, while the leaves contain only about 1-2%. The content of other branches, stems, roots, ripe fruits and other organs is even lower.
This is why it is recommended to apply top-effect inorganic nitrogen fertilizers before germination, and do not emphasize the principle of top-dressing phosphorus, potash, or compound fertilizers.
If the planted fruit tree has zinc deficiency symptoms (leaflet disease), it can be sprayed with about 3% zinc sulfate water on the tree body before germination to prevent and control; Take 0.5 ~ 1.0% borax water spray during the flowering period; if you add 0.5% urea to the water spray for mixed spraying, the effect will be better.
2. Topdressing fertilizer after physiological drop to rapid fruit expansion
A large number of studies have confirmed that during this period, fruit trees need to absorb and utilize a large amount of nitrogen and potassium and a small amount of phosphorus nutrients due to flowering, fruiting and growth.
And about 20 to 35 days after flowering is the best time for fruit trees to absorb calcium and supplement calcium fertilizer. Generally speaking, after the physiological fruit drop stops to the fruit ripening period, it can be divided into two growth stages, that is, the early stage fruit growth is the cell division stage, and the later stage is the cell expansion stage.
In the first stage of fruit growth, the lack of nitrogen and calcium will obviously affect the number of cell divisions in the young fruit, which will lead to smaller fruit and reduced yield.
In the second stage of fruit growth, lack of potassium will ultimately affect the fruit's content and appearance quality, which is manifested by low sugar content, low VC content and poor fruit coloring. Therefore, in the above-mentioned top dressing period, it is best to apply fertilizer twice, and the first time to take high nitrogen and medium potassium.
The second time adopts the principle of low nitrogen and high potassium: two top dressings, the nitrogen fertilizer used is about 1/3 of the annual amount of nitrogen fertilizer. The amount of potash fertilizer should be about 80% of the total annual amount.
In addition, during this period, 20 to 35 days after flowering, regardless of bagging or not, be sure to spray calcium fertilizer (0.5% calcium nitrate aqueous solution, or commercially available calcium fertilizer, such as high-energy calcium Calcium urate, etc.), two sprays are separated by 5-7 days.
During this period, if symptoms of iron deficiency (ie, yellow leaf disease) occur, spraying with 0.5% ferrous sulfate aqueous solution 1 or 2 times may be taken. If there is lobular disease, you can spray zinc sulfate 0.1 ~ 0.2% water solution 1-2 times.
3. Apply base fertilizer after fruit harvest
Different tree species and different varieties have different morning and evening due to the mature harvest period, and the time of applying the base fertilizer will also be different in the morning and evening. Generally, the time of applying the base fertilizer is generally from mid-late September to early November. In general, after the fruit is harvested, a heavy fertilizer combined with organic fertilizer and inorganic fertilizer should be supplemented in time.
This fertilization is very important, especially for those tree species with short growth cycle and early fruit ripening, such as peach, apricot, plum, cherry and some very early varieties.
This is because after the fruit is harvested, all the organs above the tree have stopped growing, but the root system still has a strong ability to absorb fertilizer and water, and the tree is in the weakest state. It is in urgent need of supplemental nutrition to restore the tree vigor, and Store nutrients to create good basic conditions for the growth and flowering of spring in the coming year.
Scientific research and production practices have proved that it is incorrect and unscientific for fruit tree growers all over China to get used to applying base fertilizer in winter or early spring.
The amount of organic and inorganic fertilizer applied in autumn fertilizer is about 20% of the total annual application of organic fertilizer + annual total of inorganic Phosphate fertilizer + annual total of inorganic potassium fertilizer.
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