Kenya: Farmers grow jack beans to improve soil fertility and reduce soil erosion

| September 16, 2019

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It’s mid-morning and Anne Nyangasi is leading a group of farmers who are inspecting their jack beans, also known as canavalia beans. She is growing the beans in a demonstration plot on her farm to test whether they grow well in the area. Farmers grow jack beans as a cover crop to increase soil fertility and reduce soil erosion, as well as being a food crop.

Mrs. Nyangasi says, “We started planting jack beans in March this year as a trial to see if it can adapt to the climate in this area.”

Mrs. Nyangasi lives in Igunga village in western Kenya’s Vihiga county. Here, most fields have infertile and degraded soils. To reverse the situation, Mrs. Nyangasi and other farmers in her 15-member group, Community Hands Against Poverty, or CHAP, are conducting trials on small portions of selected farmers’ fields.

Mrs. Nyangasi and five other farmers have each allocated about 500 square metres of their fields for the demonstration, planting one kilogram of jack bean seed, which they bought from a farmer in Githunguri sub-county for 2,000 Kenyan shillings ($19 US).

Mrs. Nyangasi’s jack beans are doing very well. And she plans to expand the amount of land on which she plants jack beans. She explains, “We want every farmer in this village to plant this crop. It will bring income to many households, which in turn will help them to send their children to school.”

But jack beans are not just a food crop. They also provide many benefits to the soil. Roland Bunch has been working with green manure and cover crops for about 35 years in Latin America and Africa. He says cover crops such as jack beans are a solution for small-scale farmers whose degraded soils do not retain enough water to sustain crops and who are experiencing worsening droughts that are damaging crops.

He explains: “Green manure or cover crops add large amounts of organic matter and nitrogen to the soil and control weeds by covering them. By adding organic matter to the soil each year, they can not only double smallholder farmers’ present yields, but can overcome droughts. Jack bean is one of these plants.”

Mr. Bunch adds: “Jack beans are by far the most drought-resistant of all the beans we know during their first year of growth. Furthermore, they grow quite well even in the worst of Africa’s degraded soils … They can produce more nitrogen than any other bean plant that can grow in the African lowlands.”

Mr. Bunch says that if farmers intercrop maize and jack beans, after two or three years, they can stop growing jack beans and switch to other beans—lablab beans, pigeon peas, or chickpeas. Not only will they have double or triple as much maize as previously, but they can enjoy high-protein beans to eat from the same field.

He adds: “The amount of nitrogen that jack beans can put into one hectare of soil if we manage them correctly is equal to the nitrogen in about 12 bags of urea fertilizer. This means that even on land that is so degraded, after two seasons of growing jack beans, the farmer will be able to start producing maize.”

Lorna Onzere is another farmer in the CHAP group who has a demonstration plot. She says that, though this is the first time jack beans have been grown in the area, the crop has started providing good soil cover—which is important in conservation farming. For instance, the demonstration plot in her farm has tall, well-grown jack beans with large, healthy green leaves.

Mrs. Onzere explains: “This is God’s miracle. I never expected the beans to grow to such [a] height, but now I am happy that I will produce enough yields. I think my farm is becoming fertile.”

This work was created with the support of Canadian Foodgrains Bank as part of the project, “Conservation Agriculture for building resilience, a climate smart agriculture approach.” This work is funded by the Government of Canada, through Global Affairs Canada,