Introduction

The common bean, Phaseolus vulgaris, is a herbaceous annual plant in the family Fabaceae which is grown as a pulse and green vegetable. Beans are cultivated widely worldwide, forming one of the most significant food sources in Africa and Latin america. Beans were introduced to Africa from Latin America several centuries ago. To date beans are a vital staple in Africa, providing the main source of protein. Beans are consumed in many forms; the young leaves, green pods, and fresh bean grains are used as vegetables. Consumption of bean leaves is reported from the tropics from southern and eastern Africa: South Africa, Zimbabwe, Zambia, Malawi, Tanzania, Kenya and Uganda.

Pulse crop ; In tropical Africa common bean is primarily produced and consumed as a pulse. The mature dry seeds of common bean are eaten worldwide as a pulse and the immature pods and seeds as a vegetable. In tropical Africa the bean is most typically consumed boiled, often with seasoning and some oil added. It may also be mashed or made into soup. In many parts of the world the dry seeds of common bean are canned, either alone or in tomato sauce.

Leafy vegetable; Common bean leaves are eaten as a vegetable, e.g. during the hunger months of the year when not much food is available. Consumption of the bean leaves is more prevalent in the cooler highlands of east and southern Africa.

In South Africa, the leaves are commonly eaten as a cooked green called moroqo or m'fino. In the inland highveld, the bean leaves is dried in the sun to store for the dry season. Dried morogo is frequently available year-round, in urban as well as rural markets.

The Shona, Kaianga and Zezuru people of Zimbabwe eat Bean leaves as cooked greens regularly, with a peanut paste or stew when available. In Zambia, fresh bean leaves are cut up and boiled with salt or trona (crude sodium carbonate) and eaten immediately, or dried in the sun for two or three days. In Malawi bean leaves are harvested during the pod filling stage. The fresh leaves are sundried on mats and stored in sacks. Although young leaves are preferred, older leaves are also eaten, usually cooked with sodium carbonate, trona or potash to soften them. The Chewa and other peoples eat bean leaves with peanut paste or stew

In Uganda, bean leaves are commonly eaten fresh-cooked and are dried for dry season consumption. They are used to supplement the staple food dish as a sauce, a relish added to meat and fish, and mixed with the bean seed itself. In Kenya, bean leaves are important in the higher rainfall areas where most beans are grown. Intercropping is the standard practice, usually in rows between other crops, but sometimes in small patches. The leaves are steamed, boiled or fried alone or in combination with other vegetables, depending on use and availability.

Various local spices and trona may be used to alter the leaves' consistency. Most are eaten as an accompaniment to a high-carbohydrate food stuff such as maize, sorghum, cassava, banana, etc. However in Kenya, bean leaves are not an important market commodity, even at the local level, although some will be sold, particularly in drier areas or in periods of famine or shortage.(The Beannicowpea collaborative research support program (CRSP), n.d.)

Livestock fodder; Crop residues are often used as fodder.

General Information

The common bean is typically a climbing, trailing or erect and bushy annual herb,depending on the variety being grown. The leaves grow alternately on the stems, are green or purple in color and are divided into 3 oval leaflets with smooth edges. The leaves can grow 6–15 cm long and 3–11 cm wide. The common bean produces white, pink, lilac or purple flowers which are approximately 1 cm in diameter, and bean pods 8–20 cm long and 1–1.5 cm wide which can range in color from green to yellow or black to purple. Each pod contains 4-6 smooth, kidney-shaped beans. Common bean plants are annual plants and last only one growing season and range greatly in size from the bushy varieties 20–60 cm in height; to vines or runner beans which can reach 200 –300 cm in length. (Wortmann, C.S., 2006)

Common beans do well in regions with temperatures between 15 and 27°C. The crop can tolerate the maximum temperatures of about 29. 5°C. Temperatures close to or above 35°C, and stress due to moisture during the flowering stage and pod formation may cause abortion effects to several blossoms and under development of new pods. The sufficient conditions necessary for beans growing are; rainfall range between 350 and 500 mm and relatively low humidity. Low humidity and enough rainfall are significant in controlling the risks associated with bacterial and fungal diseases.

Common bean (dry bean) varieties in Kenya 

Examples of common bean varieties grown in Tanzania

• "Canadian Wonder" (characteristics as in Kenya) 
• "Cheupe" (recommended altitude:above 1500 m, potential yield: 2.5-3.0 t/ha, seeds light brown, resistant to anthracnose, CBMV, HB and rust)
•  "Lymungo 85" ((recommended altitude: 900-1800 m, days to flowering: 33, pod colour: yellow, potential yield: 1.2-1.5 t/ha, resistant to ALS, anthracnose, CBB and CBMV)
• "Lymungo 90" (recommended altitude: 900-1800, seeds are larger than Lymungo 85, colour deep mottled red purple, yield potential; 1.2-1.5 t/ha)
•  "Selian 05" (recommended altitude: 1000-1500, potential yield: 1.0-1.6 t/ha, seeds cream in colour, resistant to anthracnose, CBMV, HB and rust) 
• "Selian 06" (recommended altitude below 1500 m, yield potential; 2.5-3.0 t/ha, seeds white, days to flowering: 40, resistant to anthracnose, CBMV and HB)

Examples of common bean varieties grown in Uganda

•  "K 132" (Seeds large kidney shaped red with white mottled colour, maturity period: 80 days, potential yield: 2 t/ha, resistant to CBMV but susceptible to anthracnose)

 Commercial varieties of French beans available in Kenya

Source: PIP Technical Itinerary French Beans. www.coleacp.org

Recently introduced French bean varieties in Kenya (HCDA)

• "Bakera"
•  "Bronco"
•  "Claudia" 
• "Coby" 
• "Cupert"
•  "Espadia"
•  "Gloria" 
• "Morgan"
•  "Pekera"
•  "Rexas" 
• "Sasa"
•  "Super Monel"
•  "Tonivert" 
• "Vernando" 

Agronomic aspects

Planting Time/Period

Beans are susceptible to extreme temperatures but do well in warm seasons. During low temperatures, plant growth is relatively low as compared to high temperatures, which records an accelerated growth rate. The plants have high adaptability to short days because they are very frost-tender, with an average minimum soil temperatures of about 18°C for better germination. Sowing of bean plants should therefore be after the last dates of frost-free. When sowing, it is essential to take account of the temperatures and the length of days to ensure favorable growing conditions. Most types of beans require a frost-free growing season of 85 to 120 days (Dulloo, M. E., et al., 2008, Claessens, n.d.)

Planting

Common bean is normally propagated by seed, the seeds may be sown by broadcasting and row planting. Sole-crop sowing rates range from 150,000–400,000 seeds per ha. With intercropping, sowing rates are less than for sole cropping (Wortmann, C.S., 2006).

Bush beans (Erect and bushy type) should be planted in rows 60–90 cm apart with 5–10 cm spacing within the rows. The climbing common bean (Pole bean type) is sown 3–6 seeds per planting hole in rows 100–120 cm apart with 40–50 cm spacing within the row. Seeds are normally sown 3–4 cm deep, but as deep as 7 cm if the soil surface is dry and not too heavy or prone to crusting. Climbing bean cultivars are more often produced in sole cropping than non-climbing types. The dense foliage in sole cropping easily creates a humid environment promoting diseases. Common bean is sometimes grown as a relay crop on residual moisture, e.g. in Malawi and southern Tanzania or intercropped with other annual or short-lived perennial crops like maize, bananas and root or tuber crops.(Wortmann, C.S., 2006, Bean | Diseases and Pests, Description, Uses, Propagation, n.d.)

Crop Management

The climbing bean type (Pole beans) should be provided with a pole or trellis to climb on to support the weight of the pods and allow light to penetrate to all parts of the plant, helping to prevent disease.

The crop is usually weeded once or twice, after which its canopy is sufficiently developed to suppress weeds. Earthing-up is often done at about 3 weeks after sowing. This should be done carefully, because common bean is liable to damage to the collar of the plant. Irrigation is uncommon except at higher latitudes with winter (dry season) production (Wortmann, C.S., 2006, Bean | Diseases and Pests, Description, Uses, Propagation, n.d).

Beans are comparatively light feeders and require as a guide line about 25-35 kg P/ ha (equivalent to 1-2 bags of Mijingu rock phosphate/ha) and 75-80 kg K/ha. Like all legumes, beans are able to fix nitrogen from the atmosphere, so do not require nitrogen fertilization. However, a soil conducive to nitrogen fixing with the natural nitrogen fixing bacteria present is preferable. Hard soils with little organic matter will not give good yields of beans, unless organic matter is provided, preferably in the form of good quality compost or well decomposed farmyard manure. For pure stands of beans, it is preferable to construct slightly raised beds of maximum 1 metre width in order to limit soil compaction around the bean plants. Application of good compost in the beds will improve yields as it will improve nitrogen fixation. Timely and thorough weeding is essential for French beans.

The first weeding should be done 2-3 weeks after emergence followed by a second weeding 2-3 weeks later. During weeding slight ridging of plants will help bean plants withstand attack of bean flies. Cultivating beans when the soil is wet encourages spread of soil-borne diseases such as anthracnose and fusarium root rot. Shallow tillage is preferred especially in the period before flowering as damage to the roots or the collar of the plant encourages soil borne diseases. Common bean can be rain-fed or irrigated. Irrigation is beneficial in semi-arid regions, with overhead irrigation preferred over flood irrigation. In peasant farming, the crop is seldom manured. Crop rotation is necessary to limit soil borne diseases such as root-knot nematodes and fusarium root rot. Fertilise the soil properly and plant French beans on hills or ridges where root rot could be a problem. Avoid furrow irrigation in areas prone to root rot and root-knot nematodes and fusarium. 

Mulching 

Mulching with straw and cut grasses helps conserve moisture, promote adventitious root development and enhances tolerance to bean fly maggot damage. 

Intercropping

Beans are excellent for intercropping with other food crops, such as maize, potatoes, celery, cucumber and can help supply the other crops with nitrogen to a limited degree. Longer season varieties of beans can fix higher amounts of nitrogen than short season varieties. Intercropping with chives or garlic helps repel aphids (KIOF - personal communication). 

Water management 

A regular water supply is essential for French beans as moisture affects yields, uniformity and quality. Water stress during flowering reduces yields, as does waterlogging. Irrigation in dry spells is recommended as 35 mm per week at planting and 10 days post emergence, followed by 50 mm per week thereafter till end of production. 

Pest and disease prevention with EM or BM 

EM (Effective Microorganisms) and BM (Beneficial Microorganisms) have been shown to prevent many diseases and a few pests in various crops when sprayed on a regular basis. These are commercial products and are readily available in Kenya. It is organically acceptable and quite cheap. 

Harvest/Post Harvest Practices

     a. Harvest

Common bean may be harvested while most pods are still green but near physiological maturity, for an early harvest of a fresh, easy to cook pulse product, but most crops are harvested when mature. French beans are harvested before the pods are fully-grown. Harvest starts 7-8 weeks after sowing in early cultivars. Pods should be picked every 2-3 days, and the number of pickings is greater in climbing than in bushy cultivars. Dry beans are harvested as soon as a considerable proportion of the pods (roughly 80%) are fully mature and have turned yellow. Some cultivars tend to shatter. Usually entire plants are pulled and further dried till ready for threshing. After threshing the beans are further sun dried to estimated 12 % moisture to avoid storage problems.

When leaves are used as a vegetable, the plant is usually not left to set seed but uprooted before flowering at three to five weeks of age. Occasionally, the leaves are picked just prior to senescence when the pods are full but not yet dry. In this case both leaves and seeds are used. The tender leaves are plucked and the shoots left to continue growing. Harvesting of the bean leaves should stop once the plants begin to flower. 

Farmer practices:

Solar drying of bean seeds before storage is essential. Also before storing, mix bean seeds with a) ashes or ash/chilli mixture b) diatomite (commercially available as Kensil Lagging from most hardware shops in Kenya) c) store completely dry seeds in a sealed container such as a metal or plastic bucket with air tight lid, checking regularly that no weevils are developing and closing tightly again.

     b. Post Harvest

The bean leaves is preserved through blanching to make them available during the dry season. To dry the bean leaves, spread themon a mat on the sun and regularly turn the leaves to allow them dry evenly. Store the dried leaves in a cool and dry place The dried leaves can be used any time of the year as a food resource.

Nutritional value information, Complimentary recipes

 1. Recipe 1- Bean Leaves in Groundnut Sauce (Chimpapila)

Ingredients

• 1.5 grams fresh beans leaves
• 400 grams groundnuts pounded
• 150 grams tomato
• 50 grams onion
• salt
• water

Cooking procedure

• Pluck leaves from the stems and wash in cold water
• Put in sauce pan, bring to boil and cook 15 minutes
• Make groundnut paste and add to the vegetables
• Add salt and keep stirring for 20 minutes to allow groundnuts to cook
• Add chopped tomato and onion and immediately remove from fire
• Stand 5 minutes and stir to blend the mixture together

Serving for 6

Recipe from Zambian Cookbook, by Sylvia C. Banda and Hector H. Banda published by CARE International in Zambia.

2. Recipe 2

Ingredients.

• Beans leaves 250gm
• 50 gm grated coconut
• 1 piece ginger
• 1 Onion
• 1 teaspoon Mustard seeds
• 1 Tablespoon Oil, preferably coconut oil
• 50 gm Raw peanuts 

Instructions.

1. Wash and cut the bean leaves into small pieces.
2. Fry mustard in the oil, once the seeds are broken, add onion, peanuts, and grated coconut into the pan.
3. Keep stirring until the grated coconut turns brown. Add the bean leaves and ginger bits into the pan.
4. Mix with salt, if you need, cover it and cook, low flame, in the steam from the leaves.
5. Shut the pan. Ready in 6 minutes It's a dry preparation.
6. If you have fresh curry leaves, chuck them in during the last two minutes of cooking.