Brassica Oleracea

Description: 

Brassicas  

Kale is one of several species referred to as Brassicas. This group of forbs includes forage rape (Brassica napus L.), kale (Brassica oleracea L.), turnips (Brassica rapa L. subsp. rapa), swedes (Brassica napus L.), and hybrids like Tyfon (a hybrid between Chinese Cabbage (Brassica rapa Pekeninensis Group) and stubble turnip (Brassica rapa Rapifera Group). 

Description and Uses 

Kale is a biennial leafy forage crops grown mostly in cool northern parts of Europe, Canada, and the United States. It resembles cabbage when young but is leafier and does not form heads. Stemless types growing to 2 feet (0.6 m) with marrow-stem types to 5 feet (1.5 m) or more. It is used almost exclusively for temporary pasture or greenchop, sown alone or in combination with annual ryegrass or oats to provide somewhat earlier grazing and easier ensiling. Kale can be spring-seeded following early-maturing corn silage fields for fall grazing or seeded in late summer or early autumn in warmer areas to provide winter grazing. 

Identification Characteristics

Type: 
Forb
Identification Characteristics: 

Four-petaled, light-yellow flowers are borne in loose clusters in the second year atop branched stems.

Climate and Soil Suitability Zones

Climate Tolerances: 

Marrow-stem types are frost tolerant, surviving temperatures down to 10 °F (-12 °C), allowing for winter grazing in mild winter areas. [USDA Plant Hardiness zone 4 for most cold-tolerant types; Jan mean minimum of -30 °F, -34.4 °C); American Horticultural Society Heat Zones 1-9 (<150 days above 86 ˚F (30 C)]. Requires 40-60 inches (1000-1500 mm) of precipitation or irrigation.

Soil Tolerances: 

Best suited to well-drained to moderately well-drained soil drainage classes. Not tolerant of soils that are of high clay texture, wet, or poorly drained. For good root growth, turnip needs a loose, well-aerated soil. Tolerates moderately acid soils (pH 5.6-7.3). Moderately sensitive of saline conditions (1.5-3 dS/m). Somewhat tolerant of water-soluble aluminum (persisted at 1-2 ppm Al3+). 

Cultivars

Kale cultivars differ markedly in rate of establishment, stem development, time required to reach maturity, and winter-hardiness. Cultivars include stemless and marrow-stem types.

Stemless type: (e.g. ‘Coleor’, ‘Premier’, ‘Keeper’) has a faster rate of establishment than cultivars which produce stems. Crop height is approximately 25 inches (64 cm) and matures in approximately 90 days, allowing two crops per year. ‘Premier’ overwinters at mid-latitudes, whereas other cultivars typically winterkill. 

Marrow-stem type: (e.g. ‘Caledonian’, ‘Bombardier’, ‘Grampian’, ‘Maris Kestral’) grows to 60 inches (152 cm) tall with 2-inch (5 cm) stems and requires 150 to 180 days to attain maximum production.  ‘Thousand-head’ kale is an older standard cultivar. It produces a woody stem with numerous leafy branches.  

Quality and Antiquality Factors

Quality Factors: 

Very high quality, highly digestible forage, with 20-25% crude protein and 65-80% TDN. 

Anti-quality Factors: 

Brassicas are often grazed with no ill effects yet, on occasion, adverse effects do occur. Brassicas have a readily digestible carbohydrate content but are low in fiber so cattle should be provided a fiber source to prevent rumen acidosis and bloat. Limit brassicas to 70% or less of total cattle diet dry matter. Interseeding brassicas with cereal grains such as wheat, rye or oats is recommended to ensure adequate fiber. Adjacent pasture, corn stalks, or palatable hay can provide additional fiber. Cattle should be introduced to brassicas slowly by limiting grazing to a few hours per day for the first week to ten days.  

Strip grazing brassicas is recommended to increase utilization and ensure uniform grazing. Most brassica-related disorders in cattle tend to occur during the first two weeks of grazing while adjusting to the forage. The primary potential disorders are polioencephalomalcia, hemolytic anemia (mainly with kale), nitrate poisoning, and pulmonary emphysema. Other possible clinical disorders include bloat and rumen acidosis, and metabolic problems such as hypomagnesemia and hypothyroidism with goiter. Glucosinolates present in brassicas are precursors of irritants that can cause colic and diarrhea. 

 

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Resources

Publications: 

Srinivas C. Rao and Floyd P. Horn, 1995. Cereals and Brassicas for Forage. Chapter 36. In: FORAGES: An Introduction to Grassland Management. Vol. 1. 5th ed., Iowa State University Press. 

Danny H. Smith and Michael Collins. 2003.  Forbs. Chapter 10. In: FORAGES: An Introduction to Grassland Management. Vol. 1. 6th ed., Iowa State University Press. 

Kenneth J. Moore. 2018. Compendium of Common Forages. Brassicas. In: FORAGES: An Introduction to Grassland Management. Vol. 1. 7th ed., Wiley Blackwell.