Brussels sprouts (Brassica gemmifera, the Cruciferae family) originated as a bud mutation in Belgium in 1875. The crop is common in Western Europe and is especially widely grown in England.
It is a biennial plant. During the first year, a stem 60 cm and more in height is formed which carries small and medium-sized leaves on thin petioles. The buds in the leaf axils give rise to very short shoots at whose apices small heads (sprouts) are formed. During the second year, the plant forms floriferous shoots, blooms (flowers) and produces seeds.
Brussels sprouts are sensitive to soil conditions. High yields of good quality fruits can be obtained with structured, loamy, permeable soil rich in organic nutrients.
Brussels sprouts are cold resistant. In marine climate, it is a late autumn (crop) culture. The optimum germination temperature is 18-20˚C, and the optimum growth temperature is 15-18˚C. During sprout formation and firming, the crop is particularly cold tolerant and withstands short periods of temperature drop down to 8-10˚C below zero very well.
Like other brassicas, Brussels sprouts require moisture at all stages of growth. At the same time, this crop endures water deficit somewhat better than other brassicas thanks to its more extensive root system.
Harvesting should be done when the sprouts are firm and compact enough. Initially, whole plants are uprooted, and then defoliated. The sprouts are kept on the stem because they start to wilt very soon after being cut off.
Brussels sprouts are used fresh for salads, for cooking soups, as garnish for meat and other courses, as well as a separate dish. It is valuable raw material for canned and frozen food industries.
Growing tips
The best preceding crops are annual legumes, cucurbits, winter cereals, early tomato and potato, and onion.
Healthy, uniform transplants are a prerequisite for high yields. These should be 35-50 days old, depending on the growing technique, and have 4-6 well-developed leaves. The planting pattern is 60 x 60 cm or 70 x 70 cm. The seeding rate is 35-50 seeds per 10 m2 of open ground. Cassette or potted seedlings become more readily established because no root system injuries occur during transplanting and, hence, there are no diseased plants. Fertilizers are applied at a rate of 700-750 g ammonium nitrate, 350 g superphosphate and 600 g potassium salt per 10 m2 (N 250, P2O5 75 and K2O 250 kg of active substance per hectare). The phosphate-potassium fertilizers are applied during autumn soil cultivation and the nitrogenous ones as supplementary fertilizing.
Systematic irrigation is a crucial factor in the cultivation cycle. Brussels sprouts are given 8 to 10 irrigations with an irrigation rate of 350-400 l per 10 m2 (350-400 m3/ha) per irrigation prior to the formation of sprouts and 400-450 l per 10 m2 (400-450 m3/ha) subsequently.
Among the plant handling features, the removal of the apical bud by pinching or stem topping is worth mentioning. This arrests vegetative growth and speeds up maturation of sprouts. The procedure is performed when the sprouts begin to become firm (normally, 4 to 6 weeks before harvesting). The Brussels sprouts yield generally varies between 1,5 and 3,0 kg per 1 m2 (15-30 ton/ha).
During the growing season, the crop may be attacked by a number of pests such as blue fleas, cabbage aphid, cabbage butterfly and cutworm, cabbage moth, and thrips. Therefore, chemical control is an essential component of the Brussels sprouts production technology.
Control measures: on discovering the first signs of infestation, sprays with insecticides such as Sumi-alpha, Zolone, Sherpa, Karate, Actellic, Volaton, etc. should be made systematically in cycles of 7-10 days. Considering that the cabbage leaf has a thick wax coating, it is advisable to admix adhesives (OP-7, skimmed milk or household soap in amounts of 30-50 g per 10 l of water) into the spray solution to increase the efficiency of the insecticide application.
The cabbage root fly, which is the most harmful insect pest attacking cabbage plants, deserves special mention. It starts to fly in mid- or late April when the soil has warmed up to 12-13˚C. The fly lays eggs on the root neck or in the soil around it. The hatching larvae penetrate the roots and gnaw passages in them. As a result, the plants begin to wilt (especially in dry, hot weather), the leaves turn leaden-blue, the growth is retarded or completely terminated and, not infrequently, the plants die.
Control measures: good cultural practices, preventive sprays (at the beginning of flight of butterflies) with the above-mentioned insecticides. Where the plants are attacked by larvae of the cabbage root fly, soil application of 0,15-0,2% Bi-58 or Basudin at a rate of 0,25-0,3 l per plant is recommended. A particularly effective control measure is preplant furrow application of pelleted phosphamide or pelleted superphosphate treated with phosphamide (Bi-58) and hilling-up of plants. Hilling-up prevents the larvae from reaching the plant and promotes adventitious root formation.
Among the diseases attacking brassicas, the most harmful are Black rot, Soft rot and Fusarium wilt.
Control measures: use of tolerant varieties, seed treatment, strict adherence to the crop sequence and good cultural practices.