Categories: Articles, Crop productionPublished On: 13th November 2023

Food for Africa: Legumes

By 7 min read

legume 3

Beans, including common beans that are eaten fresh, and the seeds of other legumes that can be dried and stored for later use, are grown and consumed throughout Africa.

These African legumes are suitable for planting under difficult environmental conditions, such as drought and high temperatures. Beans are a good source of protein and micronutrients, which is important to provide healthy food on the continent where poor nutrition has led to diet-related diseases like diabetes, heart conditions and obesity, as well as deficiencies in the diets of pregnant mothers and stunted growth in children.

Common beans, cowpeas, groundnuts, and soya beans are easy to grow and provide a high yield. In addition, they put nitrogen back into the soil to increase the soil’s fertility without the use of expensive chemical fertilisers. A small quantity of legumes can be used with or in the place of nsima or sadza, which is made from maize or cassava, and it can even replace expensive meat to a large extent.

Nutritional value of beans

Beans and legumes are the fruits or seeds of a family of plants called Fabaceae. Commonly eaten worldwide, beans and legumes are rich sources of fibre, essential vitamins and minerals, and plant-based protein. They are good sources of fibre and vegetable protein.

Cooking beans

Dry beans need to be soaked prior to cooking. This not only softens the beans so that less cooking time is required, but it also releases antinutrients that may stop nutrients from being absorbed by the body. You can incorporate beans into soups and stews with or without meat to add protein to your diet.

Health benefits

Beans and legumes have several health benefits. Eating more of them may help reduce cholesterol, help prevent heart disease, decrease blood sugar levels, and increase healthy gut bacteria.

Beans and legumes grown in Africa

Four beans, among many others, which are widely grown in Southern Africa, include common bean, cowpeas, groundnuts, and soya beans.

Common bean (Malawi: nyemba; Zimbabwe: shuga, bhinzi)

Common beans include bush and vine varieties that are grown in a wide range of environments. Bush beans do not have to be staked. Beans do not do well under hot, humid conditions, but need moder ate rainfall during the growing period, followed by a dry period for ripening. Beans do not tolerate extremely acid soils. They are attacked by a wide range of pests and diseases, but when they are regularly grown in intercrops with maize or other cereals, it may help to reduce these attacks.

Although climbing bean varieties can have higher yields than bush beans, they are only practical in environments with a longer rainy season. They produce a lower yield but over a longer period. They require staking, which is expensive, so an alternative is to intercrop climbing beans with maize. When grown as a sole crop, 70 to 80 kg of seed/ha is needed for some varieties.

Cowpeas (Malawi: khobwe; Zimbabwe: nyemba)

Cowpeas originated in Africa and is quite tolerant to heat, drought and acid soils but not to waterlogging. Cowpeas are attacked by many insects, and aphids (nyinda/nhata) are especially dangerous as they can infect cowpeas with viruses that will seriously reduce crop growth and yields. When grown as a monocrop, 25 to 35 kg cowpea seed/ha is used. Cowpea leaves are often used in relish, and the crop residues make a good feed for livestock. There are many species of rhizobium in African soils which will form nodules with cowpea, and the nodules formed can be round or odd shaped.

Soya beans (Malawi: soya, nyemba, khobwe, mtedza; Zimbabwe: soya bhinzi, shuga bhinzi, nyemba, nzungu).

Soya beans, which have hairy leaves and pods, tolerate moderately acid soils and short-term droughts. It can be grown from lowland to upland tropics. As it performs poorly under cool and shaded conditions, it is not suitable as an intercrop under densely planted tall, leafy crops.

Soya beans are attacked by a brown fungal disease or rust that can seriously reduce yields, so it is recommended to grow soya beans in rotation with other crops. When grown as a monocrop, from 50 to 80 kg of seed/ha are used, depending on seed size and planting distance. Leftover plant material from the soya bean crop can be used for livestock feed.

Groundnuts (Malawi: mtedza, Zimbabwe: nzungu)

Groundnut pods are formed underground. For best growth and production, it needs moderate (about 600 mm) rainfall during growth, followed by a dry period for ripening. Groundnuts do best on a sandy loam soil and can tolerate acidic soils, but may need calcium for good pod development. The crop is susceptible to a viral disease called rosette, which is spread to groundnut plants by aphids. About 50 kg of seed/ha are needed for monocrop groundnuts.

Growing legumes

Legumes can be grown in a number of different ways. In intercropping, the legumes are grown with other crops. The timing of the legume sowing has to be planned carefully if the crop is to complete growth before the dry season begins. It is common to grow one row of beans or cowpeas in alternation with one row of maize. With this arrangement the legume yield tends to be lower as the plants are shaded by the maize.

The advantage is that the same labour can be used to harvest the maize and legumes. For short-season legume crops, such as cowpeas, the legume is sown into the maize field a few weeks before maize harvest. Since the maize is drying down, it doesn’t shade the cowpeas so much. Alternatively, the legume can be sown into a field of newly planted cassava cuttings.

Fixing nitrogen

If sustainable development goals set by the United Nations (UN) must be achieved to end hunger by 2030 in Sub-Saharan Africa, where one third of all households are threatened by food-insecurity, cereal crop yields must increase substantially. Yields are severely limited in the region by the depletion of soil nutrients after decades of continuous cropping with insufficient fertilisation. This is the result of the inadequate use of mineral fertilisers and the lack of biomass for organic fertilisation.

That means more nitrogen is needed to increase crop yield. Besides being increasingly expensive, mineral fertilisers can harm the environment if used incorrectly. The good news is that nitrogen is abundant in the atmosphere and legumes have the ability to fix this atmospheric nitrogen in their plant tissues via symbiotic bacteria. By growing legumes before cereals and, instead of removing the plant remains from the soil, digging it into the soil before sowing could provide substantial nitrogen inputs. This will optimise the use of mineral fertilisers needed to improve cereal crop yields, thereby cutting costs.

Vine beans can be intercropped with maize so the dry stalks can be used
instead of staking.

Signs of nitrogen deficiency

All crops need nitrogen, water, sunlight, and other elements to grow and produce harvests. When the lower leaves of your plants turn yellow, it is a sign that a plant isn’t getting enough nitrogen. If the nitrogen in the soil is not fixed, the plants will not grow tall, and the yield will be low. Because crops remove nitrogen from the soil in order to grow, additional nitrogen must be added to the soil in one form or another every growing season.

Plants get nitrogen from several sources: from broken-down remains of previous crops grown on the soil, from animal manure, which in combination with the crop remains forms compost, from artificial fertilisers and from legume crops. By leaving the plant rests of legumes in the soil, nature will fix the nitrogen in the soil all by itself.

References

Duodu, K.G., Apea-Bah, F.B. (2017) African Legumes: Nutritional and Health-Promoting Attributes. Woodhead Publishing Series in Food Science, Technology and Nutrition 2017, Pages 223-269 https://doi.org/10.1016/B978-0-08-100866-9.00009-1Get rights and content https://www.sciencedirect.com/science/article/abs/pii/B9780081008669000091

Paliwal, R., Abberton, M. Faloye, B., Olaniyi, O. (2020) Developing the role of legumes in West Africa under climate change. Current Opinion in Plant Biology Volume 56, August 2020, Pages 242-258 https://doi.org/10.1016/j.pbi.2020.05.002 https://www.sciencedirect.com/science/article/abs/pii/S1369526620300546

Snapp, S.S., Cox, C.M., Peter, B.G. (2019). Multipurpose legumes for smallholders in sub-Saharan Africa: Identification of promising ‘scale out’ options. ScienceDirect https://doi.org/10.1016/j.gfs.2019.03.002 https://www.sciencedirect.com/science/article/abs/pii/S2211912418300798

Ranaivoson, L., Ripoche, A., Affholder, F., Falconnier, G., Leroux, L. (2023) Food security in Africa: growing legumes to reduce the need for mineral fertilisers? https://www.cirad.fr/en/cirad-news/news/2023/betting-on-legumes-for-foodsecurity-in-africa  Lalaina Ranaivoson

Tarirai Muoni, Andrew P Barnes, Ingrid Öborn, Christine A Watson, Göran Bergkvist, Maurice Shiluli & Alan J Duncan (2019). Farmer perceptions of legumes and their functions in smallholder farming systems in east Africa. International Journal of Agricultural Sustainability, 17:3, 205-218. Tandfonline.co DOI: 10.1080/14735903.2019.1609166 https://www.tandfonline.com/doi/full/10.1080/14735903.2019.1609166

0
0

Deel hierdie artikel.

Leave A Comment

0
0