How to prevent early-crop Chinese cabbage from failing to form heads?
1. Biological control (1) Take care to protect natural enemies such as parasitic wasps, and apply Bacillus thuringiensis var. aizawai (each gram of powder contains 10 billion spores) at 500-700 times dilution, or Qingchongjun No. 6, B.t. emulsion, etc. Apply granulosis virus preparations or collect from the cabbage field late-instar larvae that died from viral infection (infected larvae have reduced appetite and turn black in body color...
When Chinese cabbage is planted early, it often only grows leaves without forming heads, the heads are small, and yields are low. The main reasons are high weather temperatures, abundant rain, or rapid soil moisture loss, as well as severe pest and disease damage, especially soft rot, dry heart disease, downy mildew, powdery mildew, viral disease, aphids, cabbage caterpillars, etc. In addition, improper fertilization, such as too much nitrogen fertilizer, insufficient phosphorus and potassium fertilizer, and uneven water supply, is also an important cause of Chinese cabbage failing to form heads. If the following technical measures are taken to strengthen management, head formation and heading can be promoted. Increase phosphorus and potassium fertilizer application. About 25 days after planting Chinese cabbage, begin applying more phosphorus and potassium fertilizer once every 10-15 days, each time applying 25-30 grams of monopotassium phosphate per plant (dissolved in clear water and poured on), or apply diluted decomposed human and livestock manure water at 80-100 times dilution, preferably 2-3 times in succession.
Spray foliar fertilizer. From the time Chinese cabbage begins to form heads, spray the leaves once every 7-10 days with a mixture of 0.3% monopotassium phosphate, 500 times Zhuangfengyou, and 1500 times Shennongsu chelated fertilizer, for 3-5 consecutive sprays, evenly wetting all leaves, preferably until water droplets begin to drip down.
Prevent water shortage. During the growing period of Chinese cabbage, sufficient water supply must be ensured, and it must not be too much at one time and too little at another, or alternately dry and wet, so as to prevent the leaves from curling and wilting; in dry weather, in addition to watering once with clear water in the morning and once in the evening, 1.5-2 kg per plant each time, the bed surface should also be covered with wheat straw or other weeds to reduce water loss and keep the soil moist.
Control pests and diseases. Chinese cabbage affected by viral disease, soft rot, diamondback moth, aphids, and other pests and diseases will fail to form heads and fail to head. Therefore, during the head-forming period of Chinese cabbage, pay attention to inspecting the leaves. If pest or disease damage is found, continuously spray 2-3 times a mixture of 1500 times Nongdile and 1500 times Amobam, or spray a mixture of 1500 times Lesben and 1000 times Keshade for control. If soft rot occurs and causes severe damage, 500 times agricultural streptomycin should also be added.