Two Legumes with High Potential as Green Manures


The velvetbean (Mucuna spp.), is grown primarily for weed control, as a cover crop, green manure, and forage. It derives from southern Asia or Malaysia, was introduced to Florida ca. 1876, and then reintroduced to tropical or subtropical areas. It is now grown especially as a cover crop in Hawaii, Australia, the Philippiness and Malaysia, but can mature seeds as far north as Maryland or Kansas in the U.S.

On the Northern Coast of Honduras, small farmers have grown velvetbean with maize for 10 years, averaging yields of 4000-5000 lbs/ha, compared with 1500-1700 lbs/ha without the legume (CIDICCO, Milton Flores). In New Delhi, maize-velvetbean gave ca. 50% more foliage than maize-cowpeas. It practically eliminates weeds, improves soil structure and tilth.

A strong-growing short-day annual with slender stems, it grows as bushes or vines 3-18 m or longer with trifoliate leaves. Seeds are usually marbled, sometimes solid white, brown or black with pods up to 15 cm long.

The limitations of the velvetbean are that it requires a long frost-free growing season to produce pasture, 180-240 days, and does not succeed on cold, wet soils. Temperatures of 200-300C are recommended. It tolerates an annual precipitation of 380-3150 mm, temperatures of 18.70-27.10C, and a pH of 4.5-7.7. A pH 5-6.5 on a light sandy soil is optimum. Seeds mature in 100-130 days in southeastern US, and in 7-9 months in the tropics. It is reportedly tolerant to drought, laterites, poor soil, sand, and smothering weeds. When velvetbean is grown alone, 2-3 cultivations are necessary to control weeds until plants start vining, eventually forming a dense mat about 60 cm deep.

Because of the L-Dopa (levoratory form of the amino acid Dopa) content insect problems are few, it is immune to most bean diseases but very susceptible to vine rot disease. Some fungi attack this legume, as does bacterial leaf spot and a mosaic virus. It is resistant to rootknot nematodes.

The use of velvetbean(Mucuna pruriens) by village farmers of the northern coast of Honduras to produce corn, 1987, Milton Flores, CIDICCO.

Handbook of Legumes of World Economic Importance, 1981, J. A. Duke, USDA Beltsville, MD.

N.B. ECHO carries two varieties of velvetbean, a tropical non-itching variety Mucuna deeringiana, and a 90 day itching variety grown in the southern US.

17430 Durrance Rd.,
North Fort Myers, FL 33917


The jackbean (Canavalia ensiformis), a prehistoric American Indian domesticate found in the southwest United States, is native to Mexico, Brazil, Peru and the West Indies. Large-scale plantings are done in the Congo and Angola.

Jackbean is widely cultivated throughout the tropics, primarily as a green manure crop, a soil cover for erosion control, and for forage. As a green manure, it yields 4-12 MT/ha and is intercropped with sugarcane, coffee, tobacco, rubber and sisal. As a cover crop it is planted with cacao, coconut, citrus and pineapple. It is said to be unpalatable and undigestible to cattle, and therefore is preferable where animal damage is feared.

Usually grown as an annual, jackbean may become a perennial climber. Both climbing and dwarf bushy varieties are grown, stems are erect or semierect, 0.6-1.6m long and trifoliate. The seeds, oblong compressed, are white or ivory with a brownish mark near the grayish hilum. Jackbean is relatively resistant to drought, salinity and waterlogging, and reportedly is tolerant to disease, fungus, insects, low pH, sand, shade, slope and virus.

Jackbean fares best with an annual rainfall of 900-1200 mm, temperatures of 150-300C, and pH 5-6. It has been reported to tolerate an annual precipitation of 640-4290 mm, temperatures of 14.40-27.80C, and pH of 4.5-8.0. Green pods are produced in 3-4 months, ripe seeds require 180-300 days. As green manure, climbing varieties give more foliage, but they require strong supports.

Few pests attack this crop, including the fall armyworm, the pod weevil as well as the fungal root disease Colletotrichum lindemuthianum, asparagus bean mosaic virus, and some nematodes.

Handbook of Legumes of World Economic Importance, 1981, J. A. Duke, USDA Beltsville, Maryland.