Beans are one of the staple foods in Kenya. The only one that is more or equally grown food crop is maize. I think this is because in most homes there is a food made by combining the two called githeri. It is usually boiled when cooked in its simplest form but can later be garnished or fried and reconstituted into other dishes.
Among the beans there are many varieties that are grown and these will be determined by the altitude and climate of each place.
Beans growing in the field
Among the beans that are grown in my area are chelalang', nyayo, red kidney, mwitemania, wairimu, rosecoco among others. All the above are good for commercial venture as they have production of between 6 to 10 bags weighing 90 kilos per acre.
I personally prefer rosecoco for not only its production but also its flavour.
Beans can either be grown as pure stand or as is more popular inter-cropped especially with maize. The advantage of inter-cropping beans with a crop such as maize is that the beans fix nitrogen in the soil from the air. This assists in adding fertility to the soil and thus helps the maize grow faster.
The land preparation begins with clearing the land of bush and weeds. This is best when it is cut down and left in place to start decomposing so as to add organic matter to the soil. When ploughing the land , the turning over of the soil will the incorporate the dead plant material into the soil. In later years though, I became an advocate of zero tillage as it offers more benefits. Harrowing is then done to break up the big clumps of soil. In as much as beans are not fussy growers, a finer tilth is better and so repetition of the harrowing process may assist the crop thrive.
Lastly the seed is then sowed. In most farms which are small- micro holder farms, the seed drilling is usually done by hand. Holes are cut in the soil at a spacing of about 50 cm for row and 10 cm for seed to seed. A single bean per hole is sufficient. If doing inter-cropping with maize, the beans are usually planted about 3-4 weeks after the maize has been planted. This is to ensure that the maize gets ahead start as the beans are fast maturing and are ready for harvest in about 3 months. For inter-cropping, the beans are usually planted in the middle of each row of maize at a spacing of 10 cm from seed to seed.
The seed quantity required will depend on the variety of beans being planted. If the variety has bigger seeds, more will be required and the opposite is also true. Generally beans will require between 25-50 kilos per acre when grown in pure stand.
At the farm we found that inoculating the beans with a biofix really makes the plants the plants thrive and thus increase yields. The biofix is strains of bacteria called rhizobia that assist the plant in taking nitrogen from the air and adding it to the soil. We have not seen the need to fertilize with commercial fertilizer. Addition of well composted farmyard manure is usually sufficient.
The inter-cropping of beans also assists in weed control in the maize by providing soil cover. Moisture conservation is also achieved to some degree. This makes beans an important cover crop.
Weed control is the next important step that needs to be done. This is usually done by hand uprooting the weeds or using a hoe. Weeding is usually done for the first month and if done well, it will not be needed again as the beans will grow and cover the soil thus stifling the growth of weeds. The other method of weed control that can be done is through the use of chemical sprays. They however have to be specifically for beans and an agronomist or agro-vet specialist is best consulted before use.
Pests and diseases need to be looked out for. The best way is to always scout the field so as to catch them early.
Common pests in beans are black aphids, white flies and cutworms. At the first sign of these insects, a spray regime with an appropriate insecticide should be started.
Disease like bacterial wilt and black rot are common in beans but more so during heavy rains. Inoculating the seeds before planting with a bio-fungicide like trianum-p helps in controlling fungal diseases. Once disease are spotted breaking out, an appropriate spray regime should be started with a fungicide.
Once the beans are mature and have begun to dry, they are uprooted taken to be completely dried in a controlled manner. This is because if beans are let to completely dry in th field, they have a tendency of splitting open and scattering their seeds in the fields.
Once beans have been dried in the sun and are completely dried, they can then be manually or mechanically threshed, winnowed, sorted and kept for storage. They must be kept in a cool dry place as moisture will spoil the beans and make the begin to rot or germinate.
Would I do it again?
Beans are both a good for food and for business. They are relatively high in protein and offer good nutrition. Beans also when managed right can give a farmer income from their sale. They are usually in high demand along with maize as they form the staple food locally for the general population and even schools and hotels and other eateries.
The nitrogen fixation also benefits the crops grown on the same plot of land especially in a good crop rotation program.
I believe a farmer cannot go wrong by planting beans.