Field Management Techniques for Broccoli at Each Growth Stage

Broccoli is an annual or biennial herbaceous plant, native to the eastern Mediterranean coastal region. It is cultivated only to a limited extent in China, mainly for use in Western cuisine. Broccoli is rich in nutrients, containing protein, sugar, fat, vitamins and carotene, and ranks first among vegetables of its kind in nutritional content, and is known as the “crown of vegetables”.

I. Management during the seedling recovery stage

Management during this stage mainly involves cooling and moisture retention to promote early seedling recovery. In addition to using shade netting to build a shelter for shade and cooling, water must be sprinkled once each in the morning and evening. To prevent underground pests from biting through the seedlings, Mirel should be evenly scattered on the soil surface at transplanting. About 7 days after transplanting, apply a light application of human excrement and urine or a 2%-3% urea aqueous solution to promote plant growth. To prevent and reduce the occurrence of diseases, spray once with 75% chlorothalonil 600-fold solution or 50% carbendazim 600-fold solution about 10 days after transplanting.

II. Management during the rosette stage

This stage is the period of vigorous vegetative growth for broccoli, and sufficient fertilizer and water must be provided so that stems and leaves grow rapidly, laying a good nutritional foundation for obtaining high yields. During this stage, topdressing is needed twice. The first topdressing is when the plants begin to grow rapidly (about 15 days after transplanting), applying urea in holes opened between plants with a small hoe, at about 15 kg per mu; the second topdressing is carried out before the plants close the rows, when the heart leaves begin to show a twisting-heart shape (about 30 days after transplanting), applying fertilizer in shallow furrows opened between rows together with weeding, then earthing up, applying 20-25 kg of compound fertilizer per mu, or 25 kg of peanut bran. Where conditions permit, it is best during this stage to apply human excrement and urine once every 7-10 days. In the early rosette stage, watering should be sufficient to meet the needs of rapid plant growth and development; after the plants form a full rosette, watering should be appropriately controlled to promote underground root development. Side shoots appearing at this stage should be removed promptly to promote the formation of the main curd. At the same time, pay attention to the prevention and control of pests and diseases, especially the damage of diamondback moth (commonly known as hanging-thread worm), cabbage white butterfly (commonly known as cabbage caterpillar), black rot and soft rot. For diamondback moth, spray for control from the peak hatching period of eggs to the 2nd-instar larval stage with 5% fipronil 3000-fold solution or 1% insecticidal agent 3000-fold solution, etc.; for cabbage white butterfly, spray for control with Bt emulsion 1000-fold solution, or fenvalerate 1500-4000-fold solution, etc.; for black rot and soft rot in the early stage of disease onset, alternately spray with 200 mg/L agricultural streptomycin, or 200 mg/L chloramphenicol, or 75% chlorothalonil 600-fold solution, or 77% copper hydroxide 500-800-fold solution, etc.

III. Management during the curd-forming stage

To promote the transformation from vegetative growth to reproductive growth and favor curd formation, nitrogen fertilizer should be appropriately controlled during this stage, with combined application of phosphorus and potassium fertilizers and trace fertilizers such as boron and molybdenum. At the beginning of curd formation (40-50 days after transplanting), apply a heavy fertilization once, with 15 kg of potassium chloride and 15 kg of compound fertilizer per mu. To reduce yellowing of the curd surface and hollow stems, and to delay plant senescence, spray the leaf surface with 0.5% borax and 0.5% ammonium molybdate solution during the curd-forming period, about once every 1 week, for 2-3 consecutive applications. Throughout the curd-forming period, the field soil should be kept moist, and diseased leaves and old leaves should be removed promptly, and pests and diseases should be controlled. For cultivation that also harvests side curds, keep 3-4 robust side flower shoots per plant, and the remaining side flower shoots should preferably be removed.

IV. Management during the peak harvest stage

During this stage, attention should be paid both to promptly removing diseased leaves and old leaves to facilitate ventilation and light penetration and promote the accumulation of nutrients in the curd, and to controlling moisture to prevent excessive humidity, which can cause diseases and curd rot. In acid rain or heavy fog weather, water should be sprinkled promptly to wash away the fog moisture and acid rain, so as to reduce curd rotting. The suitable harvest period for broccoli is relatively short. If harvested too late, the curd becomes loose, the flower buds turn yellow, and quality declines; but if harvested too early, the curd is small and the yield is low. Generally, the suitable harvest time is when the flower bud granules feel somewhat loose to the touch or the flower bud granules at the edge of the curd are slightly loose, and the curd surface is tight and smooth without bumps. Broccoli harvesting is best done in the early morning or evening on a clear day. When harvesting, cut off the curd together with about 10 cm of tender fat flower stalk, place it in a shaded and cool place, and package it for market as soon as possible. If it cannot be marketed in time, it must be quickly stored at low temperature. For cultivation that also harvests side curds, topdressing should also be applied once after the main curd is harvested, at about 15 kg of compound fertilizer per mu, and the side curds should be harvested when they grow to about 5 cm in diameter.