1. Characteristics of Fertilizer Requirement of Chinese Cabbage
Chinese cabbage is a high-yield vegetable, and the yield per mu can be as high as 10000 kg. To form such a high yield, we need enough nutrients to ensure it. According to the actual planting experience, every production of 1000㎏ Chinese cabbage needs to absorb nitrogen (N) 1.8~2.6㎏ and phosphorus (P2O5) 0.9 ~1. It can be seen that the demand for potassium in Chinese cabbage is obviously higher than that of nitrogen and phosphorus. The demand for nitrogen, phosphorus and potassium in different growth stages is also quite different, which has the characteristics of less absorption in the early stage and a sharp increase in the later stage, that is, the absorption of nitrogen, phosphorus and potassium in seedling stage accounts for a small amount of the whole growth stage, which rises sharply in the heading stage and reaches the peak. Different varieties have similar laws.
The absorption of three nutrients by Chinese cabbage is that the greater the growth, the more it absorbs. Under the condition of the same fertility, applying different amounts of nitrogen, phosphorus and potassium fertilizer, or even not topdressing, this fertilizer requirement law of Chinese cabbage is similar.
Second, the formula fertilization of Chinese cabbage
1, Chinese cabbage base fertilizer
When preparing soil before sowing, apply 4000~5000㎏ fully decomposed organic fertilizer, 30 ~ 50㎏NPK compound fertilizer or 20 ~ 30 ㎏ diammonium phosphate+10~20㎏ potassium sulfate per mu, and harrow the soil after rotary tillage.
2. Topdressing Chinese cabbage
(1) Top dressing of Chinese cabbage at seedling stage
Generally, no fertilizer is applied at seedling stage. If the seedlings are weak, nitrogen fertilizer can be applied at one time, and 1% urea can be sprayed on the leaves or 5-7.5 ㎏ urea can be topdressing per mu. Before intertillage, apply chemical fertilizer on both sides of the seedling with the spacing of 10- 12 cm, and then intertillage.
(2) Top dressing in the rosette stage of Chinese cabbage
After Chinese cabbage enters the rosette stage, the outer leaves form and develop rapidly, which requires timely fertilization. The specific method is as follows: after Chinese cabbage seedlings are watered, when the soil moisture is suitable, a shallow ditch with a depth of 8- 18-20 cm is opened in the middle of the ridge, and high-quality organic fertilizer with decomposition and subdivision of1200-1500 is sprinkled into the ditch per mu.
(3) Top dressing at heading stage of Chinese cabbage
At heading stage, the aboveground and underground parts of Chinese cabbage are in a vigorous growth stage, and the demand for fertilizer has reached a peak, so key fertilizers should be applied again. Apply 20-25 ㎏ ammonium bicarbonate or ammonium sulfate per mu of water; After interval 1 water, topdressing with 20-25 ㎏ ammonium bicarbonate or ammonium sulfate per mu 1 time; In the middle stage of nodulation, topdressing per mu 1 time, ammonium bicarbonate or ammonium sulfate 15~20㎏.
In a word, the topdressing of Chinese cabbage should master the following principles: light fertilization at seedling stage and heavy fertilization at heading stage. In the process of growth, foliar fertilizer can also be sprayed, usually once every 7~ 10 days, 3~4 times. When spraying foliar fertilizer, it is best to choose it in the early morning or after 4 pm on a calm sunny day.
The above is the law of fertilizer demand and formula fertilization of Chinese cabbage. It can be seen that fertilization at rosette stage and heading stage should be re-applied in Chinese cabbage planting, especially at heading stage, which determines the yield and quality of Chinese cabbage.