The growth and development of Chinese cabbage can be divided into two stages: vegetative growth and reproductive growth. The vegetative growth period can be divided into the following periods:
1] Germination period: The germination period is from seed germination to digging and exposing true leaves. It takes about 3-5 days under suitable temperature and soil moisture conditions.
2) Seedling stage: from the exposure of true leaves to the spreading of 5-8 leaves to form the first leaf ring. It takes about 12- 15 days for early-maturing varieties to produce 5 leaves at seedling stage. It takes about 17- 18 days for late-maturing varieties to grow 8 leaves at seedling stage.
3) Rosette stage: After seedling stage, two leaf rings will form a rosette. The young and delicate leaves in the center of the plant begin to gather, which is the characteristic of the end of the rosette period. During this period, it takes about 20-2 1 day for early-maturing varieties and 27-28 days for late-maturing varieties.
4) Nodulation stage: from heart lobe to lobular formation. It takes about 25-30 days for early-maturing varieties and about 50 days for late-maturing varieties.
5) Dormancy: Due to the cold climate, bulbs are forced to go into dormancy. There is no dormancy period in areas with warmer winters such as Guangdong.
After vernalization at low temperature, Chinese cabbage can enter the reproductive growth stage under long sunshine, and the process can be divided into three stages: bolting stage, flowering stage and pod setting stage. The transition from vegetative growth to reproductive growth of Chinese cabbage generally requires low-temperature vernalization conditions of 2- 10 degrees Celsius and 10-30 days, and the requirements for late-maturing varieties are stricter than those for early-maturing varieties. In some areas of Guangdong, due to the warm winter, the conditions of low-temperature vernalization of Chinese cabbage can not be met, and late-maturing Chinese cabbage often can not pick flowers and harvest seeds.
Chinese cabbage likes mild and cool climate conditions, and the suitable growth temperature is in the range of 10-22 degrees Celsius. It will not grow well above 25 degrees Celsius, and it will not adapt to it above 30 degrees Celsius. /kloc-It grows slowly below 0/0℃, stops growing below 5℃, and is resistant to light frost and heavy frost. Chinese cabbage needs sufficient light conditions during its growing period to facilitate photosynthesis, accumulate more substances and promote ball formation. Because of the large number of leaves, large leaf area, thin cuticle on leaves and large water transpiration, it is necessary to ensure adequate water supply during the growth period. There is little water demand at seedling stage, but the root system is underdeveloped and the water absorption capacity is weak, so it is appropriate to keep the soil moist. During the rosette stage, the leaf area expands rapidly and the water demand increases greatly, so it is necessary to replenish water in time. The water demand is the highest in the nodulation period, so it is necessary to ensure that there is enough water in the soil, but the water should be controlled in the late nodulation period to facilitate the storage of leaf bulbs. Chinese cabbage is the product of vegetative organs, with large yield per unit area and high requirements for soil nutrients. Nitrogen, potassium and phosphorus are the main nutrients absorbed, and more nitrogen is needed in the early stage and more potassium is needed after granulation. Every 1000 kg of Chinese cabbage needs to absorb about 1.5-2.5 kg of pure nitrogen, 0.7-0.9 kg of pure phosphorus and 2-3.5 kg of pure potassium. It accounts for 10-20% of the total fertilizer absorption from seedling stage to fruiting stage, and 80-90% of the total fertilizer absorption at fruiting stage.