Botanical and biological features

The cauliflower (Brassica oleracea var. botrytis cauliflora D.C.) is an annual plant belonging to the Brassicaceae family. Cauliflower is more sensitive to growing conditions than other brassicas are. The root system of cauliflower is less extensive than that of cabbage and is characterized by a relatively poor ability to absorb nutrients from the soil.

Cauliflower is less tolerant of low temperatures as compared with cabbage. Although germination can occur at 5–8˚Ñ, long periods of temperatures below 8˚Ñ tend, later on, to slow down the process of head formation and to lower the head quality. The optimum growth temperature is 18–20˚Ñ. At economic maturity, the plants are the least resistant to frosts and are injured at temperatures 2–3˚C below zero. Exposure to high temperatures shortly after the beginning of curd formation may result in leafy curds. Formation of small, underdeveloped curds may be due to exposure to relatively low temperatures (10˚C or lower) for a period of time as long as a few weeks. Initially, cauliflower plants fail to react to a temperature drop like this, but later on, after 5 to 7 leaves have developed, formation of small, underdeveloped curds may occur – the so called premature curd development. The formation of small, underdeveloped curds may also occur due to transplanting of overgrown seedlings or root injury resulting from waterlogging or root disease and/or other departures from proper crop management practices. ‘Ricy’ curd (loose or protruding flower buds creating a ‘ricy’ appearance) is a condition caused by lack of optimum temperature conditions or by wide temperature variations during curd development. These variations in temperature may also be due to overhead irrigation of cauliflower plants during curd development.

When a temperature drop or other stressful conditions (extreme temperatures, poor soil conditions, drought, insufficient fertilizer application, etc.) occur at the plant growth stage, the apical point and, consequently the curd, may fail to develop and in early spring the apical point may completely disappear. This phenomenon is termed ‘sterile flower’. The occurrence of this disorder depends on weather or growing conditions. Some cauliflower varieties are characterized by a higher genetically determined susceptibility to this disorder than others. ‘Sterile flower’ is usually a problem with early spring sowings. The disorder may occur in areas with wide temperature variations. The best way to prevent this disorder is to avoid too early plantings and to use cauliflower hybrids suitable for the chosen sowing dates.

Cauliflower has especially high light requirements during seedling production. It is a moisture-loving crop. It has particularly high soil and atmospheric moisture requirements during leaf formation, heading and head expansion. During this period, the optimum soil humidity (soil moisture content) should be 75–80% of field moisture capacity, and the relative air humidity should be 85–90%. Cauliflower prefers light, water-rich, deep soils rich in humus and available nutrients. This crop responds very well to organic and mineral fertilizers.

Growing tips

The best preceding crops are annual legumes, cucurbits, winter cereals, and onion. The planting pattern is 70–90 õ 40–45 cm, such that the plant density is 2.5–3.5 pl/m2. The seeding rate is 50–60 seeds per 10 m2. Higher planting densities tend to delay maturity by several days.

With autumn soil cultivation, fertilizers are applied at a rate of 500 g of nitroammophoska per 10 m2 (N 80, P2O5 80, K2O 80 kg of active substance per hectare). During the growing season, 2 to 3 supplemental fertilizer applications are made at a rate of 400 g of potassium nitrate and 150 g of ammonium nitrate per 10 m2 (N 100, K 180 kg of active substance per hectare). It is also good practice to apply magnesium sulfate at a rate of 600 g per 10 m2 (Mg2O 100 kg of active substance per hectare). The fertilizer application rates are adjusted according to the nutrient status of the soil.

With cauliflower, deficiency of micronutrients such as boron and molybdenum is often the case. Therefore, it is good practice to use micronutrient complex fertilizers (Terraflex, Kemira, Master) applied to the root zone and foliar-applied micronutrients (Speedfol, Rexolin, Wuxal).

During the growing season, cauliflower is given 5–10 irrigations, the water application rate being 350–400 l per 10 m2 (350–400 m3/ha) per irrigation. Water deficit causes a drop in yield and, occasionally, the reddening of curd. Systematic irrigation is a crucial factor in the cultivation cycle. Combining drip irrigation with application of water-soluble fertilizers through the drip irrigation system (fertigation) is a highly efficient technique resulting in a more uniform moisture and fertilizer distribution in the root zone, more efficient water use, less soil compaction, and no soil crust formed. Readily soluble mineral fertilizers are given with each water application.

Cauliflower can be grown from early spring till late autumn. It can also be used as a second double crop after early harvested preceding crops.

To ensure good head quality, it is necessary to bind together or break partway 2 to 4 upper (outer) leaves to provide a tight wrap to prevent sunlight from reaching the curd. The color of the curds may turn yellow due to exposure to the sun. It is not advisable to touch the curd with hands during wrapping for protection against sunlight, harvesting and shipping; otherwise the curd quality will deteriorate.

The diseases and the control measures are similar to those in white cabbage.

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