(4) Apply the ball fertilizer. The ball-forming period is the period in which the product is formed, and the assimilation is the strongest, so the amount of fertilizer and water is large. Applying the ball-forming fertilizer 5-6 days before the wrapping, it is necessary to use a large amount of fertilizer that lasts for a long time, especially the potassium fertilizer. In general, 20 kg of ammonium nitrate is applied, and 10-15 kg of superphosphate and potassium sulfate are used as ball-forming fertilizer. In order to make the nutrients last, it is best to mix the fertilizer with the decomposed manure, and it is advisable to open a deep groove of 8-10 cm between rows. This top dressing has the effect of enriching the inner ball of the leaf ball to enhance the quality of the Chinese cabbage. Metal House,Prefab Metal Frame House,Prefab Metal House,Metal Frame House Foshan Shengbang Steel Structure Co.,Ltd , https://www.fssbssteel.com
Chinese cabbage originated in China and is one of the specialty vegetables in China. The quality of the leaf ball is soft and nutritious. The nutrients contained in it are vitamin C, B1, B2 and calcium, phosphorus and iron. They are indispensable nutrients for the human body. At the same time, it is also one of the most zinc-containing vegetables, especially for children's intellectual development. Chinese cabbage grows rapidly, has a short growth period, and has high yield. It is a vegetable with a large amount of fertilizer. Cabbage leaves as a product and is most sensitive to nitrogen requirements. When the nitrogen supply is sufficient, the chlorophyll is increased, and the production of carbohydrates is increased, which also promotes the growth of the leaf ball and increases the yield. If there are too many nitrogens and the phosphorus and potassium are insufficient, the cabbage plants are long, the leaves are large and thin, the ball is not tight and the water content is high, the quality is decreased, and the disease resistance is weakened. Phosphorus can promote the differentiation of leaf primordia, so that the outer leaves occur faster, the differentiation of the leaves increases, and it also promotes its transport to the leaf. Fully supply of potash fertilizer, so that the cabbage leaves are full, the yield is increased, and the nutrient content in the cabbage is increased to improve the quality.
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First, the fertilizer requirement of cabbage
Each 100 kg of cabbage produced about 150 grams of nitrogen, 70 grams of phosphorus, and 200 grams of potassium. In the case of 5000 kg per mu, it absorbs about 7.5 kg of nitrogen, 3.5 kg of phosphorus and 10 kg of potassium. The approximate ratio of the three elements is 1:0.47:1.33. It can be seen that the most absorbed potassium is followed by nitrogen and phosphorus. The absorption of three elements in different growth stages of Chinese cabbage is different, which is roughly proportional to the growth of dry weight of plants. The germination period to the rosette period is only about 10% of the total absorption, while the ball-forming period absorbs about 90%. The proportion of the three elements absorbed in different periods is also different. The nitrogen absorbed by the rosette to the rosette is the highest, followed by potassium and phosphorus. During the balling period, the potassium is absorbed the most, followed by the nitrogen, and the phosphorus is still the least. This is because during the ball-forming period, cabbage requires more potassium to promote the production of photosynthetic products in the outer leaves, and a large amount of potassium is required to promote the transport and storage of photosynthetic products from the outer leaves to the leaf cells. The effects of specific nutrients are as follows:
(1) Within a certain range of nitrogen use, the yield of Chinese cabbage increased with the increase of nitrogen use. The main reason for the increase in production is to increase the cotyledon area and thickness, rather than increasing the number of leaves. The reason for increasing the application of nitrogen fertilizer to thicken the leaves is that the cell population is not enlarged due to the expansion of the cell volume. 
(2) Phosphorus promotes the cell division of plant growth points, accelerates the differentiation of new leaves, and forms rosettes. Phosphorus also accelerates the roots of the main roots, expands the contact surface with the soil, and absorbs more water and nutrients. Phosphate fertilizer is sufficient, root tip cells and heart leaves grow faster, which is conducive to the formation of leaf cells. The increase rate of phosphorus is lower than that of nitrogen, but the application of phosphate fertilizer on the basis of applying nitrogen fertilizer can increase the vegetable yield and improve the firmness of the leaf. 
(3) Potassium can increase the sugar content of Chinese cabbage, increase the ratio of sugar to nitrogen, and accelerate the ball-forming speed. According to the analysis, the sugar content in the leaves is higher than that in the outer leaves, and the sugar content in the petiole is higher than that in the leaves. In the growth period, the sugar content during the ball-forming period is higher than that in the rosette stage, and the sugar content in the rosette period is higher than that in the seedling stage. In the formation of the leaf ball, in order to transport the organic matter to the product organ, a large and full leaf ball is formed, which requires a lot of potassium fertilizer. If potassium is deficient, the rosette leaves will gradually yellow when the leaf ball is full, the photosynthetic efficiency is greatly reduced, and the disease resistance of the plants is also weakened. 
(4) In addition to the three elements of nitrogen, phosphorus and potassium, Chinese cabbage also needs other nutrients. At present, the most prominent production is calcium and boron. In the cabbage period, harvest period and storage period of the Chinese cabbage, it is often found that the edge of the young leaves inside the leaf ball is browned and dried (no rot and odor), and the vegetable grower is called “dry heartâ€. The main reason is that the soil is deficient in calcium, or the soil is dry, the application of nitrogen fertilizer is too much, the concentration of soil solution is too high, the root absorption of calcium is hindered, and the antagonism of sodium, potassium and ammonium on calcium. In addition, excessive humidity and transpiration may lead to calcium deficiency in the Chinese cabbage; Symptoms of boron deficiency on plants.
Second, fertilization technology
(1) Apply enough base fertilizer. Cabbage has a long growing period, and the base fertilizer should be based on organic fertilizer, with appropriate quantitative fertilizer. Generally, the amount of manure in the mu land is not less than 5,000 kilograms. Before the cultivated land, 60% of the manure is scattered in the ground and deep into the soil. Before the depression, 40% of the manure is scattered on the ground and into the shallow soil, and then ridges. Fertilizer can be applied with single chemical fertilizer and compound fertilizer. Generally, 15 kg of urea, 15 kg of diammonium phosphate and 15 kg of potassium sulfate are applied, or 35-45 kg of compound fertilizer with 45% nutrient content is applied. 
(2) skillfully apply seedling fertilizer. After the cotyledon of Chinese cabbage grows, the main root has reached about 10 cm; and the first-order lateral roots have the ability to absorb water and absorb fertilizer. In the case of insufficient or no fertilizer application, a small amount of seedling fertilizer should be applied, 5 per acre. -7 kg of urea to promote its growth. When applying fertilizer, it is important to apply small seedlings and weak seedlings to promote the formation of strong seedlings. 
(3) Apply the fertilizer. The rosette leaves growing in the rosette stage are the organs that will produce a large number of photosynthetic products in the future during the ball-forming period. Fully fertilizing and watering is the key to ensure the strong growth of the rosette leaves, but at the same time, it is necessary to prevent the rosette leaves from growing and causing the heart to end. “Fat fertilizer†should be applied when there are a few plants in the field to start the group. Generally, 800-1500 kg of manure is applied to the mu, 50-100 kg of plant ash, and 7-10 kg of phosphorus and potassium. Direct fertilization of cabbage should be applied to the small ditch of 8-10 cm on the edge of the plant and the soil should be covered. The transplanted cabbage is applied to the gully, and the soil is mixed well and then planted. If there is a long-term phenomenon in the late period of the rosette, it is necessary to take the "small seedlings" measure. 
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