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Brassica rapa L.

Syn.: Brassica campestris L.
Brassicaceae
Turnip, Turnip greens, Turnip rape, Field mustard

Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.

  1. Uses
  2. Folk Medicine
  3. Chemistry
  4. Toxicity
  5. Description
  6. Germplasm
  7. Distribution
  8. Ecology
  9. Cultivation
  10. Harvesting
  11. Yields and Economics
  12. Energy
  13. Biotic Factors
  14. References

Uses

Turnips are one of the most commonly grown and.widely adapted root crops, as general farm crop, truck crop, or home-garden crop. Roots eaten raw or cooked as a vegetable, and tops as potherb like spinach. Roots also grown for feeding to livestock during fall and winter.

Folk Medicine

The powdered seed is said to be a folk remedy for cancer. The root when boiled with lard is used for breast tumors. The stems and leaves are said to be a remedy for cancer, while a salve derived from the flowers is said to help skin cancer. (Hartwell, 1967–1971).

Chemistry

Per 100 g, the root is reported to contain 30 calories, 91.5 g H2O, 1.0 g protein, 0.2 g fat, 6.6 g total carbohydrate, 0.9 g fiber, 0.7 g ash, 39 mg Ca, 30 mg P, 0.5 mg Fe, 49 mg Na, 268 mg K, a trace of b-carotene equivalent, 0.04 mg thiamine, 0.07 mg riboflavin, 0.6 mg niacin, and 36 mg ascorbic acid (Watt and Merrill, 1963). Per 100 g, the leaf is reported to contain 23 calories, 92.7 g H2O, 1.9 g protein, 0.2 g fat, 4.6 g total carbohydrate, 1.0 g fiber, 0.6 g ash, 168 mg Ca, 52 mg P, 2.6 mg Fe, 78 mg Na, 420 mg K, 1330 mg b-carotene equivalent, 0.10 mg thiamine, 0.18 mg riboflavin, 0.7 mg niacin, and 47 mg ascorbic acid (Wu Leung et al., 1972). Seed oil contains large amount of erucic, linoleic, and linolenic acids.

Toxicity

Occasionally suspected of poisoning bovines, sheep, and pigs.

Description

Biennial herb with swollen tuberous white-fleshed taproot, lacking a neck; leaves light to medium green, hairy or bristly, stalked, lyrate-pinnatifid, 30–50 cm long, stem-leaves sometimes glaucous with clasping base; flowers bright yellow, sepals spreading: petals 6–10 mm long, those in anthesis close together and commonly overtopping the unopened buds; outer 2 stamens curved outwards at base and much shorter than inner stamens; fruit 4–6.5 cm long, with long tapering beak, on divaricate-ascending pedicels 3.2–6.5 cm long; seeds blackish or reddish-brown, 1.5–2 mm in diameter. Fl. and fr. second spring.

Germplasm

Varieties may have white or yellow flesh, and outside crown may be white, green or purplish-red. Most common white-fleshed varieties are: 'Purple Top White Globe' and 'White Egg'. 'Shogoin' is a white-skinned, white-fleshed Japanese variety, widely grown in the South for greens and salad. Yellow-fleshed turnips include 'Golden Ball' or 'Orange Jelly', 'Amber or Yellow Globe' and 'Yellow Aberdeen'. 'Seven Top' is grown in South for useof greens. 'Purple Top White Globe' is recommended for tropics. Brassica rapa subsp. rapa, turnip, cultivated for its tuberous taproot, sometimes escapes as a weed. Brassica rapa subsp. oleifera DC., Turnip rape, grown as a fodder crop, has larger reddishbrown seeds and non-tuberous taproot. Brassica rapa subsp. sylvestris (L.) Janchen (B. campestris L., p.p.). Field mustard is a weed or ruderal in much of Europe, native to Asia. Reported from the China-Japan, Eurosiberian, and Mediterranean Centers of Diversity, turnip, or cvs thereof, is reported to, tolerate aluminum, bacteria, disease, frost, fungi, high pH, low pH, laterite, mycobacteria, photoperiod, smog, sulfur dioxide, virus, and weeds (Duke, 1978). Terrell (1977) divides Brassica rapa into the following groups: Chinensis Group—pak-choi, Pekinensis Group—pe-tsai or "Chinese cabbage", Perviridis Group—spinach mustard, Rapifera Group—turnip, and Ruvo Group—ruvo kale. (2n = 20)

Distribution

Cultivated in Europe for over 4000 years, probably native to central and southern Europe, now spread throughout world, including most parts of the tropics.

Ecology

Turnip is basically a cool climate crop, resistant to frost and mild freezes. Grown as a spring or fall crop throughout the United States. Temperatures below 10°C cause bolting. Turnips do well in deep, friable, highly fertile soil with pH 5.5–6.8; sandy loams are used for early markets roots and greens. Short growing season makes them very adaptable as a catch crop. Ranging from Boreal Moist to Rain through Tropical Thorn to Moist Forest Life Zones, Brassica rapa is reported to tolerate annual precipitation of 3.5 to 41.0 dm (mean of 75 cases = 9.1), annual temperature of 3.6 to 27.4°C (mean of 75 cases = 10.7), and pH of 4.2 to 7.8 (mean of 66 cases = 6.2) (Duke, 1978, 1979).

Cultivation

Seed sown thinly in spring, summer or fall in drills at seed rate of 1.1–2.2 kg/ha. Seedlings then thinned to stand 5–15 cm apart in rows 0.3–0.9 m apart. Cultivate shallowly for weed control. Add lime to soil to correct pH to 5.5–6.8. Only light applications of fertilizer are justified, as 450–675 kg/ha of 4–12–4. When turnips are seeded as a fall crop following a crop that has been well fertilized, no additional fertilizer may be necessary. Seed may be broadcast on fertile, well-prepared seedbeds where weed control will not be difficult. Turnips may be intercropped with corn, and as such they are shade-tolerant, or they may be used as a catch crop after early vegetables. It is not advisable to grow turnips after a root crop. Good rotation, helps to control diseases. Best grown after clover, beans, peas or grass crop (Reed, 1976).

Harvesting

Roots may be harvested in 45–80 days. They are harvested for bunching when 5 cm in diameter, and for topped turnips when 7.5 cm in diameter. Turnip greens may be harvested when plants are young and tender. For early spring market, turnips are pulled, washed, their tops left on, tied in bunches, and marketed. Topped turnips for the general market are sold by the bushel or the hundredweight. Flavor and texture are not improved by storage. They should not be left in the ground where temperatures near freezing occur; in milder areas they may be left in field until desired. They may be stored in pits or piles, in well-drained soils. Piles should not be more than 2.6 m wide nor more than 2 m deep to prevent heating at the center. For good aeration, wooden chutes are inserted at intervals of 2.5–3 m in the pile. A ditch is dug around the base of pile for water runoff. Alternate layers of straw and soil are used as covering for pit storage. For indoor storage, crates or small piles laid on earth cellar floors are satisfactory. Small quantities of turnips may be stored in a cool cellar and covered with moistened clean sand to keep them from drying out. Storage temperature in a cellar or in a cold storage room should remain between 0° and 1.5°C, with a relative humidity of 90–95%.

Yields and Economics

Good yields are 12.5 tons/bunched or 25 tons/topped per hectare in the United States. However, these figures do not represent true yields since it is difficult to determine what proportion of a crop is sold topped, bunched or fed to livestock. Turnip crop in 1969 was ca 60,000 MT; the 1971 consumption was ca 50,000 MT. The national consumption for both turnips and rutabagas (these are usually reported together) is ca 200,000 MT, not counting quantities used for animal feed. Turnips and turnip greens are available all year, with peak production in October and November. Duke (1978) reports fresh turnip yields of 65 MT/ha.

Energy

According to the phytomass files (Duke, 1981b) annual productivity ranges from 4 to 11 MT/ha. Indian studies showed DM yields of 530–1,260 kg/ha after 38 days with 61–191 kg extractable protein; 820–2,090 kg/ha after 52 days with 90–265 kg extractable protein. If this much were available in 45 days, and plots were cropped continuously (perhaps impractical, if not impossible), DM yields might run 6–16 MT/ha with ca 800–2,000 kg/ha, the residues remaining for potential energy conversion. Seed yields in Minnesota and Canada run over 1,000 kg/ha/yr, and the oil from such seeds is being considered for energy purposes (Matai et al., 1973).

Biotic Factors

Cross pollination, by various insects, is necessary for good seed production. In USSR, 16–17 colonies of bees/ha are used, but 2 or 3 hives are sufficient to increase pollination and to insure good seed set. Isolation of varieties necessary for pure seed production; in England at least 900 m; in New Zealand, 400 m. Should be well-isolated from all other forms of B. juncea, B. campestris, and B. napus. Clubroot (Plasmodiophora brassicae) and Black rot are the most serious diseases. Other fungi attacking turnips include: Albugo candids, Alternaria brassicae, A. brassicicola, A. oleracea, A. herculea, A. tenuis, Botrytis cinerea, Cercospora albo-maculans, C. brassicicola, C. brassicae, Choanephora cucurbitarum, Cladosporium cladosporioides, Colletotrichum higginsianum, Corticium solani, Cystopus candidus, Curvularia inaequalis, Erysiphe polygone, E. communis, Fusarium oxysporum, F.conglutinans, Gloeosporium concentricum, Leptosphaeria napi, Macrophomina phaseoli, Macrosporium macrosporum, Mycosphaerella brassicicola, Oidium erysiphoides, Peronospora parasitica, P. brassicae, Phoma lingam, Phymatotrichum omnivorum, Pythium ultimum, Rhizoctonia sp., Sclerotinia sclerotiorum, Sclerotium rolfsii, Septomyxa affine, Stemphylium botryosum, Streptomyces scabies, Spongospora subterranea. Turnips may be parasitized by Orobanche cernua, or attacked by the following bacteria: Agrobacterium tumefaciens, Bacterium aroideae, Erwinia carotovora, E. aroideae, Pectobacterium carotovorum, Pseudomonas maculicola, P. madrasensis, Xanthomonas campestris, and X. vesicatoria campestris, and X. vesicatoria. Viruses isolated from turnips include: Beet mild yellowing, Beet ringspot, Cabbage blackspot, Cauliflower mosaic, Crinkle mosaic, Cucumber mosaic, Kukitachina mosaic, Turnip latent, Turnip mosaic and Curly top. Nematodes attacking turnips include: Belonolaimus longicaudatus, Ditylenchus dipsaci, Helicotylenchus dihystera, H. pseudorobustus, Heterodera cruciferae, H. schachtii, Meloidogyne arenaria, M. hapla, M. incognita, M. i. acrita, M. javanica, Nacobbus aberrans, Pratylenchus neglectus, P. penetrans, P. projectus, and Trichodorus christiei. Turnip aphid, root maggot and flea beetles are the most injurious insect pests.

References

Complete list of references for Duke, Handbook of Energy Crops
Last update Tuesday, December 30, 1997