Proper field establishment

Beans are short term crops and grow very fast, especially green beans, which are ready to harvest 7 to 8 weeks after planting, while the dry beans are ready in 10 to 12 weeks. Beans, therefore, need proper attention and suitable growing conditions in order to maximise yields.

Preparing land by hand can be done with a hoe or a spade. Except in cases of noxious weeds like spear grass or couch grass, it is not necessary to completely turn the soil. Loosening and breaking up clods is sufficient. Stones, sticks and weed roots must be removed. If heavy animals such as oxen are used to till the soil, care must be taken to work the land only when it is dry.

Green bush beans should be sown in rows 60 cm apart and 10 cm between the plants for comfortable picking. Climbing beans should be sown in double rows and a larger spacing of 80 cm between rows and 100 cm between each double row.

Sharing experiences on the establishment of bean gardens (bush and climbing beans)

Inquire about farmers’ experiences with establishing a bean crop by asking the following questions:

What are your experiences with regard to field establishment of
bush and climbing beans?
Have you experienced any challenges?
How have you tried to address them?

Land preparation

Beans can develop deep roots, provided that the soil is well structured. The soil should be loosened and any noxious weeds like couch grass (Cynodon dactylon) should be removed. If the plot was previously covered with weeds like Amaranthus spp, which produce a lot of seeds, then the land needs to be prepared early in the season. This will encourage most of the weed seeds to germinate as soon as the soil gets any moisture. They can then be lightly tilled down before beans are planted; very shallow cultivation is needed, only along the topsoil, to remove these weeds. Compost or animal manure should be added earlier during the first cultivation to allow for any weed seeds carried along to also germinate before the final tilling session before planting.

Discussion on common practices of bean crop management

Invite the farmers to share their experiences:

How do you set up bean fields?
What field activities are performed after planting and how often?
What else do you think needs to be done in order to encourage proper growth and good bean yields?

Intercropping and crop rotation

Beans can be grown either as a monocrop, or intercropped with other crops such as maize, cassava or sweet potatoes.

Although a bean monocrop is preferable for large scale production for efficient crop management and harvest, intercropping presents more benefits especially for small scale farmers:

Higher production per land unit;
Crop biodiversity contributes to natural pest regulation:
Higher yield security. If one of the intercrops does not develop well, the farmer will get a harvest from the other crop.

Intercropping beans with other crops such as maize, bananas or tubers (yams, cassava, and sweet potatoes) is widely practiced and brings good results. Only 30 % of all beans in Africa are grown as monocrops, 50 % is intercropped with Maize, 10 % with Banana, 10 % with roots/tubers and 2 % with Sorghum. For example:

Intercropping 2 to 3 maize plants with 6 bean plants per square meter can result in a 100 % yield for both crops.
The yield of sweet potato intercropped with beans does not significantly differ from a monoculture of sweet potatoes. The recommended plant density is 3.3 sweet potatoes and 10 bean plants per square meter.
Intercropping cassava with beans also gives excellent results, provided the cassava variety is not too vigorous and late branching. The yields reach 80 % for the cassava and 100 % for the beans.
Intercropping bananas with beans has a positive effect on the banana yield and provides a 50 % bean yield compared to a monoculture of beans.

Beans used for intercropping are usually of determinate growth. Climbing beans can hinder or even suffocate the main crop. Towards the end of a maize growing season, climbing beans can be sown that use the dry maize stalks for support and use residual soil moisture.

Beans in a monocropping system must be grown in rotation with other crops. It is not advisable to grow beans for two consecutive seasons on the same field. Beans leave a nitrogen-rich soil allowing subsequent crops to therefore benefit and grow successfully. Examples of crop rotations with beans include root crops (cassava, sweet potatoes), cereals (maize, rice, sorghum) and vegetables (cabbage, tomatoes, onions).

Plant support

Bush beans with determinate growth do not need any support material. Indeterminate bush beans may have to be supported with twigs or grown together with maize or cassava as support plants.

Climbing beans must be grown on some kind of trellis. The trellis should not be higher than 2 metres in order to make picking easier. When the beans reach the top of the trellis, the growing point of the main shoots should be pinched out. This reduces height and increases the growth of lateral shoots.

There are several ways to construct a trellis:

Single sticks - They must be made of sturdy material since they are prone to falling or breaking in strong winds. Around each pole 6 to 8 seeds should be planted in a mould. After appearance, the weakest plants are removed and the strongest 5 are left.
Wigwam construction - Three or four poles are tied together at the top forming a pyramid, which is more stable than a single pole. The poles are often made of mature elephant grass, tall reeds, bamboo or cassava stems. At the base, the poles are fixed in the soil 80 cm apart.
Tent construction - Double rows of poles are tied together in pairs perpendicular to the seedbed. The pole pairs are interconnected at the top with a horizontal slat, thus forming a long tent. The feet of the pole pairs are 80 cm apart, the pole pairs 100 cm apart. The advantage of this construction is that less sturdy material such as reed can be used. The disadvantage of tent and wigwam constructions is the cumbersome harvest of beans hanging inside of the foliage, as well as the suboptimal exposure to sunlight and ventilation of the plants.
Single row trellis - A sturdy pole is placed every 4 meters of the plant row. A metal wire is strung between the poles at a height of 2 metres. Strings are tied to the top wire and hang down as a support for the climbing beans. Alternatively, a wire or nylon net with a mesh width of 10 to 10 cm is hung from the top wire. This system offers ideal illumination and ventilation of the crop. The costs of the material, however, may prove prohibitive.
Live trellis - Live materials such as maize or cassava are intercropped and used instead of sticks, poles or wires as support material for the beans. Maize stems from a previous maize harvest are left standing to support the climbing beans. Other materials such as cassava stems can be constructed either as single sticks, single rows, wigwam or tent to support beans. The cassava develops roots so it becomes more stable. However, it needs regular pruning so that it does not overshadow the beans.

Improving soil fertility

Although beans can be grown on practically all soil types, deep, well drained sandy loams with a moderate pH are ideal. Unproductive soils can be improved by employing the following approaches. First is preventing soil organic matter loss. Second is incorporating organic material (e.g. green manures, compost or animal manure), which will increase organic matter and nutrient levels in the soil.

a. Soil conservation

Beans are delicate plants and susceptible to breakage by wind or running water from uphill, even in gently sloping areas. It is therefore highly advisable to grow beans (bush or climbing) as an intercrop within taller and stronger plants such as maize and cassava. In addition, proper terracing is needed to protect against soil and organic matter loss.

b. Addition of organic materials

Beans require modest amounts of nitrogen because of the symbiosis with Rhizobium bacteria that transform atmospheric nitrogen into nitrogen available to the plants. In poor soils, a small amount of nitrogen from a nitrogen rich source should be supplied before sowing to benefit the initial growing phase when the rhizobia are not yet active. Rhizobia develop better and faster in soil to which compost has been added.

Organic materials such as animal manure or compost should be applied to the land such that they are well incorporated into the soil during land preparation for planting. Animal manure or compost will make an important contribution to maintaining and increasing soil fertility. Soil fertility can also be increased by growing green manure crops and digging or ploughing them into the soil. Crop residues should be composted before application in order to benefit the beans. Fresh manure should be avoided because it attracts the bean fly. Therefore only composted manure should be applied to the bean fields. It is usually better to give a good supply of animal manure to the previous crop in the rotation, then the beans will not need any additional applications.

Sharing information on local soil fertility management in bean production

Inquire among the farmers about their approach to soil fertility management in bean fields asking the following questions:

Do you grow beans with any other crops together or in rotation?
Do you apply any organic manure to the fields before or after planting?
Identify any shortcomings with the methods used and recommend appropriate modifications.

Proper weed control

Weeds contribute to biodiversity in the field, but compete with beans for water, nutrients and light. Weed control in bush beans is necessary until the bean foliage covers the rows, thereby inhibiting weed growth. Weeding is carried out with a hand or mechanical hoe. Along with hoeing, the rows should be ridged for better plant stability, protection of the plant collar and the formation of lateral roots. Ridging also covers weeds in the row. Weeds in the row that do not suffocate or that cannot be removed mechanically are pulled out by hand. During first hoeing, ridging is done when the bean plants are about 15 cm high.

Because climbing beans never completely cover the soil between the rows, weed control has to be carried out for a longer period than for bush beans, especially in the first half of the growing cycle. Weed growth in the second half of the growing cycle does not significantly influence the yield, but weeds should not be allowed to seed.

Proper pest and disease management

Beans suffer from a number of pests and diseases. The major insect pests in order of importance are aphids, cutworms, bean stem maggots (bean fly) and storage pests such as bruchids (bean weevil). The diseases in order of importance include bean mosaic viruses, blight, leaf rust, root rots, anthracnose and angular leaf spot. Organic management of pests and diseases in bean production is based on an integrated preventive package, which encourages that a range of practices are applied simultaneously to prevent the introduction and spread of pests and diseases. Individual management of specific pests and diseases is difficult in beans since they are very short term crops. The use of synthetic pesticides is not allowed in organic bean production.

Pests and diseases can be effectively managed in the bean garden by using the following approaches:

Use of improved varieties - Choose improved varieties with good yield potential and, if possible, resistant to common diseases or tolerant to major pests and adapted to local environmental conditions. Seeds should be obtained from approved seed suppliers or carefully selected to avoid introduction of seed-borne disease like viruses.
Proper field management - Vigorously growing plants are more resilient and can tolerate pest and disease infections. Growing a healthy crop begins by choosing a suitable growing location that has loose, fertile soil, which helps quick emergence to avoid pests such as the bean fly. Fresh manure should not be applied in the bean garden in order to avoid the bean fly.
Early planting - To avoid water stress and proper weeding early planting is recommended. Early planting will also enhance quick growth of the bean plants. Pests can be regulated by encouraging functional biodiversity. This is where natural enemies of pests are encouraged to develop and propagate unhindered. Beneficial insects will build up their population and prey on plant pests, for example the Syrphid fly (hover fly), a common predator of aphids, can prey also on the bean aphid. Since many beneficial insects depend on nectar and pollen of host plants, it is advisable to plant flowering plants along the boundaries or terraces within the garden.
Plant hygiene - Another effective preventative measure is plant hygiene. Remove any plants with virus symptoms from the field and burn or bury them. Disease infested plant material should not be left in the field, but made into compost. The plot should then be rotated with other crops, meaning beans or other legumes should not be grown on the same plots for any 2 consecutive seasons.
Sulphur compounds - Spray sulphur compounds at a 0.2 % concentration at the first signs of rust infection. Some varieties are susceptible to sulphur, make trial sprayings before treating the whole crop. On small plots, following regular scouting for pests, botanical plant extracts (such as Tephrosia, Tithonia, Marigold, Datura and Neem leaves) can be used to eliminate any evading pests.
Management of storage pests - The most damaging storage pest reported by dry bean farmers is the bean bruchid (bean weevil) Acanthoscelides obtectus. Proper drying and clean storage is the best control for bean weevils or bruchids. Botanical plant dried leaves (such as Tephrosia, Tithonia, Marigold, Datura) are also effective in controlling the bean weevil if mixed with the beans before storage.

Field visit to identify bean pests and diseases

If possible, visit different bean fields and identify any observable signs of pest or disease problems. Inquire about identification and knowledge on pests and diseases by asking the following questions:

Are you familiar with the signs of pest and disease infections identified?
Have you monitored to see when these pests and diseases are most likely to attack and the damage caused?