Field Management Techniques for Broccoli at Different Growth Stages

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

Morphological Characteristics

Shape

The morphological characteristics and growth habits of broccoli are basically similar to those of common white cauliflower (cabbage). It belongs to the Brassicaceae family, Brassica genus, cabbage species, and is an annual or biennial herbaceous plant. It grows vigorously and has strong heat tolerance and cold resistance. The plant is tall; depending on the variety, about 20 leaves grow before the flower stem emerges, with flower buds clustered at the top. They are tightly clustered into a head shape, hemispherical in form, with green flower buds, hence the name green cauliflower.

Leaves

The leaves are blue-green and alternate, gradually turning dark blue-green, with a thickened waxy layer. The petioles are narrow and long, and leaf shapes include broad-leaf and long-leaf types. The root stem is thick with a thin epidermis, the pith cavity in the center has high water content and is tender, and the root system is well developed.

I. Management during the seedling recovery stage

Management during this period mainly involves cooling and moisture retention to promote early seedling recovery. In addition to using shade nets to build shelters for shade and cooling, watering is required once each in the morning and evening. To prevent underground pests from biting off seedlings, Mireor is evenly scattered on the soil surface at transplanting. About 7 days after transplanting, a light application of night soil or a 2%-3% urea water solution is applied to promote plant growth. To prevent and reduce disease occurrence, about 10 days after transplanting, spray once with 75% chlorothalonil 600-fold solution or 50% carbendazim 600-fold solution.

II. Management during the rosette stage

This is the period of vigorous vegetative growth for broccoli, and sufficient fertilizer and water must be provided so that stems and leaves grow quickly, laying a good nutritional foundation for high yield. During this period, topdressing is needed twice. The first topdressing is when the plant begins rapid growth (about 15 days after transplanting), using a small hoe to open holes between plants and apply urea, about 15 kg per mu; the second topdressing is done before the plants close the rows, when the heart leaves begin to twist inward (about 30 days after transplanting), combining weeding with opening shallow furrows between rows, applying fertilizer and then hilling soil, with 20-25 kg of compound fertilizer per mu, or 25 kg of peanut bran. Where conditions permit, it is best to apply night soil once every 7-10 days during this period. In the early rosette stage, watering should be sufficient to meet the needs of rapid plant growth and development; after the plant forms a rosette, watering should be appropriately controlled to promote underground root development. Side branches appearing at this stage should be removed promptly to promote formation of the main curd. At the same time, attention should be paid to pest and disease control, especially the damage from diamondback moth (commonly known as hanging silk worm), cabbage white butterfly (commonly known as cabbage caterpillar), black rot and soft rot. Diamondback moth can be controlled by spraying 5% fipronil 3000-fold solution or 1% insecticide 3000-fold solution from the peak hatching period of eggs to the 2nd instar larval stage; cabbage white butterfly can be controlled by spraying Bt emulsion 1000-fold solution, or fenvalerate 1500-4000-fold solution; for black rot and soft rot in the early stage, alternate spraying 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.

III. Management during the curd formation stage

To promote the transformation from vegetative growth to reproductive growth and facilitate curd formation, nitrogen fertilizer should be appropriately controlled during this period, with combined application of phosphorus, potassium and trace fertilizers such as boron and molybdenum. At the beginning of curd formation (40-50 days after transplanting), apply a heavy fertilizer 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 delay plant aging, spray the leaf surface with 0.5% borax and 0.5% ammonium molybdate solution during curd formation, about once every 1 week, continuously 2-3 times. Throughout the curd formation period, field soil should be kept moist, and diseased leaves, old leaves should be removed promptly and pests and diseases controlled. For cultivation that also harvests side curds, keep 3-4 healthy side flower branches per plant, and the remaining side branches should be removed.

IV. Management during the peak harvest stage During this period, attention should be paid to promptly removing diseased leaves and old leaves to facilitate ventilation and light penetration and promote nutrient accumulation in the curd, while also controlling moisture to prevent excessive humidity, which can cause disease and curd rot. In acid rain or heavy fog weather, water should be sprinkled promptly to wash away fog water and acid rain to reduce curd rot. The suitable harvest period for broccoli is relatively short; if harvested too late, the curd becomes loose, flower buds turn yellow, and quality declines, but if harvested too early, the curd is small and yield is low. Generally, the suitable harvest time is when the flower bud particles feel slightly loose to the touch or the flower bud particles at the edge of the curd are slightly loose, and the curd surface is tight and flat without bumps. Broccoli harvest should preferably be carried out in the early morning or evening on sunny days. When harvesting, cut off the curd together with about 10 cm of tender flower stem, 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 be applied once after harvesting the main curd, about 15 kg of compound fertilizer per mu, and side curds should be harvested when they grow to about 5 cm in diameter.