How to Grow Bambara groundnut

Vigna subterranea · Also called: Bambara bean, Bambara nut, Njugu mawe, Nyimo, Ntoyo, Okpa, Epa roro, Gurjiya

A young bambara groundnut plant growing in pale sandy stony soil, with several leaves divided into three leaflets on long upright stalks rising from a single crown at the ground, on an open field with sparse scrub and scattered trees behind.

Photo: Yq2Yq, CC0 (Wikimedia Commons)

Bambara groundnut is Africa's own crop and one of the toughest food plants in the world. It was domesticated in West Africa, it is grown across the drylands from Senegal to Tanzania and on into Indonesia and Malaysia, and it produces on poor sandy ground in seasons that leave groundnut and cowpea with nothing. It is grown overwhelmingly by women, mostly on small plots, mostly for the household. Its real distinction is nutritional: it carries starch, protein and some fat all in the one seed, which almost no other pulse does, so a family eating bambara groundnut is close to a complete meal from a single crop. Its honest drawback is the cooking. Dry bambara seed takes three or four hours on the fire, and in a household gathering its own firewood that is a real cost which no yield figure ever shows.

Growing Bambara groundnut, Stage by Stage

1. Get the land ready — Choose light sandy ground that drains, work it loose, and resist the urge to enrich it.
2. Choose your seed and planting material — Use fresh shelled seed of a local kind, because local landraces are what have survived your seasons.
3. Sow the seed — Sow shallow into warm moist soil at the start of the rains, giving each plant room to spread its crown.
4. Water — This is a drought crop grown on rain, and what it cannot take is wet ground while the pods are ripening.
5. Weed and earth up — Weed early and then stop, and draw loose soil up around the crown so the pods have somewhere soft to form.
6. Flowering and pod set at ground level — The flowers open at the soil surface and then bury themselves, which is the strangest and most important thing about this crop.
7. Watch for trouble — Most of the trouble in this crop is leaf disease in a wet year and weevils in the store afterwards.
8. Harvest — Lift the whole plant when the leaves yellow, and pick the pods off the base rather than trying to pull them singly.
9. Dry, shell, store and cook — Dry the pods hard, shell only what you need, store against weevils, and plan for a long cooking time.

Common Problems & Troubleshooting

If you see: Large healthy dark green plants with plenty of leaf and almost no pods when you scrape at the base or lift one.

It likely means: The ground was too rich, or nitrogen was applied. This crop makes its own nitrogen, and extra pushes it into leaf rather than pod.

Do this: Do not apply nitrogen or fresh manure to bambara groundnut at any stage.

If you see: Flowers at the soil surface that never turn into pods, with the little stalks behind them stopping against a hard crusted surface rather than pushing in.

It likely means: The soil at the base of the plants has set hard. The pod stalk is soft and cannot push through a crust.

Do this: Draw loose soil up around the crown of each plant while it is still safe to work near them, before flowering begins.

If you see: Far fewer pods than flowers, with small broken stalks visible at the base of the plants where you have been hoeing or walking.

It likely means: The pod stalks were broken off by weeding, hoeing or walking through the crop after the ground-level flowers appeared.

Do this: Finish all weeding before the flowers appear at the soil surface, and then leave the crop alone.

If you see: Pods that are rotten, mouldy or already sprouting when you lift the crop, sometimes with seedlings coming up in the row.

It likely means: The ground was wet while the pods were ripening, or the crop was left in the ground after the rains returned.

Do this: Lift the crop as soon as the leaves yellow rather than leaving it in the ground.

If you see: Small brown or dark spots with paler edges spreading across the leaves in wet weather, joining up until the leaves dry and fall early.

It likely means: Leaf spot, the commonest disease of this crop, which spreads by rain splash and is worst in a wet season on a crowded stand.

Do this: Space the plants properly so that air moves between them rather than sowing too thickly.

If you see: Small round holes in the seed and fine dust in the bottom of the container, with hollow seeds when you open them.

It likely means: Storage weevils. They often come in with the harvest and multiply quietly in the store over months.

Do this: Store the crop in the pod rather than shelled, since the shell is real protection.

If you see: Dry seed that is still hard after two hours on the fire, using far more firewood than the meal is worth.

It likely means: This is normal for the crop rather than a fault. Dry bambara seed is hard and genuinely takes three or four hours unless it is prepared first.

Do this: Soak the seed overnight before cooking, which shortens the time on the fire considerably.

Yield & Market Value

Growing the crop is only part of the job. The last part is knowing what a normal harvest looks like where you are, and knowing what your seed is worth before you agree a price with anybody.

Remember It This Way

If you forget every other page of this guide, keep these lines. They are the whole crop, in order, short enough to carry in your head.

Poor sandy ground on purpose. Rich soil gives leaves, not pods.
No nitrogen, ever. It makes its own.
The flowers open at the soil, and the pods bury themselves.
Keep the soil loose at the base. A crust stops the pods forming.
Weed hard early, then stop. Every broken stalk is a lost pod.
Lift when the leaves yellow, and go over the ground twice.
Do not leave it in the ground once the rains come back.
Dry until the seed rattles, and store it in the pod.
Soak overnight or it takes four hours and a lot of firewood.
Eat some fresh in season. It cooks in a fraction of the time.

Test Yourself: Identification

What is this small plant with leaves in threes on a dry sandy field?

Why is this yellow flower down in the soil instead of up on the plant?

Why are these pods so many different colours, and why are they being pounded?

Honest Limits of This Guide

Yield figures for this crop are unusually unreliable, because most of it is grown on small household plots outside any market and is never counted, and because some figures are for pods and others for shelled seed. Every number here is a rough idea of scale only.
Timings are given in days and seasons rather than in months, because bambara groundnut is grown across a wide band of Africa and Asia where the rains arrive at very different times. Your harvest comes when the leaves yellow, whatever the calendar says.
Very little is registered for use on bambara groundnut anywhere, because it is a minor crop almost everywhere it is grown. This guide therefore concentrates on soil, spacing, timing and storage, which are what a grower actually controls.
Local landraces differ enormously in how long they take, what colour the seed is and how well they stand drought, and no guide can tell you which is right for your rainfall. The kinds your neighbours already keep are the best available evidence.

Sources

GBIF Backbone Taxonomy species-match record for Vigna subterranea (L.) Verdc. — Global Biodiversity Information Facility (GBIF), Copenhagen (source)
EPPO Global Database — Vigna subterranea (EPPO code VIGSU) — European and Mediterranean Plant Protection Organization (EPPO), Paris (source)
FAOSTAT crops and livestock products — production data for bambara beans — Food and Agriculture Organization of the United Nations (FAO), Rome (source)
Vigna subterranea (bambara groundnut) — CABI Compendium datasheet — CABI, Wallingford (source)

Laisha knows Bambara groundnut better than this page can show.Photo diagnosis for pests and disease, live market prices, and an agronomist you can ask at two in the morning. Ten days free, no card. After that 10 US dollars a month, one price worldwide.Start ten free days