Detailed Explanation of Management Techniques for Chinese Cabbage During the Head-Forming Stage

When Chinese cabbage enters the head-forming stage, its water consumption is greater than in the earlier period, so irrigation must be used to supplement it, keeping moisture uniform and the supply adequate. Avoid alternating between too much and too little, or between dry and wet. The specific requirements are: the first watering at the head-forming stage should be light, as too much water will harm plant growth; 4-5 days after the first head-forming watering, move to normal irrigation, generally once every 5-7 days, with each irrigation applying no less than 30 cubic meters; stop watering one week before harvesting, first to prevent excessive moisture that reduces storability, and second to make harvesting easier and reduce losses from mechanical damage.

Topdressing during the head-forming stage should mainly consist of fertilizers applied with irrigation water. The first topdressing should be applied before Cold Dew, and the second a few days before Frost's Descent. During this period the temperature gradually drops, so the topdressing should mainly be quick-acting nitrogen fertilizer, generally ammonium sulfate, applied at 20-30 kg per mu with irrigation water. For plots where head formation is somewhat poor, the topdressing amount should be appropriately increased. Topdressing should be stopped in the later period to prevent excessive vegetative growth of the Chinese cabbage.

Pest and disease control. Pesticide application should be stopped half a month before harvesting Chinese cabbage. During the head-forming stage, Chinese cabbage requires focused control of downy mildew, black spot, soft rot, black rot, bacterial angular leaf spot, aphids, cabbage caterpillars, beet armyworm, and others. Apply pesticides according to the target, with scientific and timely control. Spraying should be thorough and meticulous, ideally covering both the upper and lower surfaces of the leaves. Combine chemical control with physical control; where conditions permit, insect-killing lamps or yellow sticky boards may be used to trap and control pests.

Specific pesticide applications:

(1) Disease control: Downy mildew: spray 72% cymoxanil-mancozeb wettable powder at 600-800 times dilution; or 69% dimethomorph-mancozeb wettable powder at 800-1000 times dilution; or 72% curzate wettable powder at 600 times dilution. Black spot: spray 50% iprodione wettable powder at 1000 times dilution; or 80% mancozeb wettable powder at 600-800 times dilution. Soft rot and black rot: use 72% agricultural streptomycin at 4000 times dilution, or 77% copper hydroxide wettable powder at 500 times dilution. If soft rot or black rot infected plants are found, they should be promptly pulled out, taken outside the field, and deeply buried; the diseased planting holes should be disinfected with quicklime or chemicals, then filled with soil and compacted, to prevent the pathogen from spreading during watering or after rain. Bacterial angular leaf spot can be controlled with 4000 times dilution of cellomycin.

(2) Pest control: To control beet armyworm, use 1.8% abamectin at 3000 times dilution; to control diamondback moth and cabbage caterpillar, use 2.5% spinosad suspension concentrate at 1000-1500 times dilution; to control snails, use snail-killing granules.