How to grow Bambara groundnut

Choose light, sandy or sandy-loam land that drains well. Keep off low spots and heavy, sticky soil that holds water — there the pods rot, and hard ground won't let them push in.

Loosen the soil deeply, about 15–20 cm — a hoe-blade or spade's depth — so the roots go down and the surface stays soft.

Break up every clod and rake the top into a fine, crumbly tilth (soft, crumbly soil). The pods must push into soft surface soil, so make the top layer especially loose.

Level the surface so water can't pool. On a slope, work across the slope, not up-and-down, to hold the rain and stop the soil washing away.

Get seed of a local type (a landrace — a traditional variety you can save and re-grow) that does well in your area: well-filled, whole, unbroken seed of a known colour. Because bambara pollinates itself, you can save and re-use your own seed year to year — it does not lose strength the way hybrid maize does.

Pick out plump, whole, undamaged seed. Throw away any with small round holes, loose powder, or shrivelled, mouldy grains — those carry weevils or won't grow.

Buy the small amount of phosphorus your recommendation gives for your field (for example single superphosphate, or a low-nitrogen compound). Phosphorus builds strong roots and helps fill the pods. Do not buy nitrogen top-dressing — on a bean it only grows leaf, wastes your money, and can cut your pod yield.

Bambara also likes calcium to fill its pods, just as the groundnut does. Well-rotted manure and a little clean wood-ash supply it — no special fertiliser is needed.

Store seed and fertiliser dry, off the floor, away from food, water and children. Keep planting seed in its pods until sowing — the whole pod shields the seed from weevils.

Use only well-rotted manure or compost — dark, crumbly, no strong smell. Fresh, strawy dung needs more months to rot down.

Spread it thinly and evenly — a light sprinkle, not a thick blanket. Because bambara is a light feeder, a light dressing is plenty; your recommendation gives the amount for your field.

Work it into the topsoil about one to two weeks before you sow, so it settles in and doesn't sit in lumps.

Sow into warm, moist soil — on a good rain, or when the soil is damp a hand's-depth down. This is a drought crop: it does not need a big soaking like maize, just enough moisture to sprout.

Make your rows about 40 cm apart — two hand-spans — and drop one seed every 15–20 cm along the row — about a hand-span. This gives a good dense stand (roughly 100,000–150,000 plants a hectare); tighter spacing gives even more seed.

Set one seed per station, about one finger-joint deep (3–5 cm) — at the shallow end, about 3 cm, on soils that dry into a hard crust, so the shoot can break through.

Drop the small amount of phosphorus your recommendation gives right in the hole or furrow with the seed — phosphorus does not scorch seed the way nitrogen does, so it can sit beside it.

Cover and firm the soil gently over seed and fertiliser, so the seed sits snug in moist earth and comes up evenly.

Every 3–4 days (from about 5 days after sowing), walk the young crop in a large 'W' across the field, so you cover all four corners and the middle — not just the edge by the path.

Check the growing tips and the underside of young leaves for aphids — tiny soft green or black insects clustered together, often with sticky, shiny 'honeydew' (their sap-waste), ants running about, or curled, puckered young leaves.

Bambara is tough, so don't rush to spray. Small aphid numbers are held down by ladybirds and other helpful insects. Act only if colonies build thickly on the growing points and no helpful insects are working — then squash them or wash them off with a little soapy water.

Also count the gaps — stations where nothing came up — so you know whether to re-sow (see the emergence check).

About 1–2 weeks after sowing (7–14 days), walk the rows and count how many stations have a seedling up against the number you sowed.

Work out the share that came up — for example, 85 seedlings from 100 stations = 85%.

85% or more, evenly spread → a good stand, carry on.

Below 85%, or big blank patches → the check has failed: re-sow the gaps now with fresh seed into moist soil, by about two weeks after sowing at the latest, so the fill-ins aren't left far behind the rest.

Weed at about 3 weeks after sowing (around 18–25 days), before the weeds grow bigger than the crop and before flowering starts.

Weed shallowly — scrape or pull just below the surface. Deep hoeing tears the crop's roots and dries out the soft topsoil the pods will need.

Take weeds out roots and all where you can; chopping only the tops lets many grow straight back.

In dry areas, leave the pulled weeds lying between the rows as a light mulch (a soil cover) to hold moisture.

Weed again at about 5 weeks after sowing (around 32–40 days), before the leaves grow together and cover the ground (before the canopy closes) and before the pegs start going down.

Keep it shallow and light — the plant is now spreading and starting to flower, so deep hoeing damages the roots and the coming pegs.

Pull any big weeds close to the plants by hand rather than hoeing hard against them.

Every 3–4 days, walk the 'W' through the crop and look closely at leaves and growing tips on plants spread across the whole field.

Leaf spot (a common leaf disease): look for small dark brown or reddish-brown spots on the leaves, sometimes with a paler yellow ring around them, worse in warm, humid, wet spells. A few spots are normal and need nothing.

Aphids: look for clusters of tiny soft green or black insects on the tips and under young leaves, with sticky honeydew or ants. Squash small colonies; leave the rest to ladybirds where you can.

Step in only if leaf spot is spreading fast over most plants, or aphid colonies are building thickly on the tips — otherwise note it and move on.

From about 6 weeks after sowing (around 40 days) until the pods are set (about 70 days), weed only by hand, gently pulling weeds close to the plants.

Do not hoe among the plants — a hoe cuts the pegs that are pushing the pods into the ground.

Keep the surface soil loose and open around the base, so the pegs can push in easily.

You may draw a little loose soil up to the base to give the pegs soft soil and make lifting easier later — but never cover the crown (the central growing point), or you smother the plant.

Only if you irrigate: through flowering and pegging (about 30–70 days after sowing), give a moderate watering every 7–10 days to keep the soil evenly moist.

Water in the cool of the day, and let the surface dry a little between waterings — the crop hates sitting wet.

Avoid waterlogging — soggy soil rots the young underground pods. Drain any low spots.

Once a week (from about 30 days after sowing), look over the flowers, the low stems and any pods sitting near the surface, on plants across the field.

Look for pod-sucking bugs — small to medium green, brown or shield-shaped bugs, and narrow long-legged brown ones, sitting on the flowers and stems; they often drop or fly off when disturbed. Look too for shrivelled flowers and dark feeding spots.

A few bugs do little harm here. Act only if many gather — knock them into a tin of soapy water by hand in the cool of the morning, when they are slow.

If numbers are high and you choose to spray, cover skin, nose and eyes, spray in the cool with the wind behind you, keep it off food, wash afterwards, and respect the waiting time on the label before harvest (the pre-harvest interval).

Only if you irrigate: from about 70 days after sowing through pod-fill, water lightly every 10–14 days to keep the soil evenly moist — steady is the aim, never wet.

Avoid late waterlogging — soggy soil now rots the filling pods underground, where you can't see the damage until you lift.

As the leaves begin to yellow and die back near maturity, stop watering and let the crop dry down in the field, ready to lift.

Once a week, walk the crop and look over the leaves and the general health of the plants.

Rust: on the underside of the leaves, look for reddish-brown, powdery spots that rub off like rust-coloured dust on your finger; badly hit leaves yellow and dry early. Watch too for late dark leaf spots as before.

Root-knot worms (nematodes — tiny soil worms): watch for patches of stunted, yellow, wilting plants that don't perk up even after rain. Gently lift one — knotted, swollen lumps like beads on the roots mean root-knot.

These are mostly mild. If a patch is badly hit, lift that patch a little early rather than lose it — and don't plant bambara or other beans on that spot next year; rotate to a cereal like millet or maize to starve the worms out.

Harvest when most plants have yellowed and started to die back — about 90 days or more after sowing, depending on your local type. To be sure, lift one plant and check the pods: ripe pods are full and firm, and the seed inside is hard, not soft or milky.

Choose a dry spell, and if the ground is hard, loosen the soil first with a hoe or fork all around each plant, so the pods don't tear off and stay behind.

Pull or lift the whole plant with its roots, and hand-pick the pods off the roots and stalks.

Search the loosened soil under and around each plant for any pods that dropped off — these are easy to miss and are pure lost harvest.

Gather the pods into baskets or bags for drying; if some plants are still green, leave them a few more days and lift them in a second round.

If a test plant shows soft pods or soft, milky seed, it is not ready — wait and check again in a week or two. If pods are already loose in the soil or sprouting, harvest at once and dig carefully to recover the buried ones.

As soon as the pods are off the plant, spread them in the sun on a mat, rack or tarpaulin — never on bare ground — for several days, turning them so they dry evenly. Cover them or bring them in if rain threatens.

Dryness test: the pods should be hard and rattle, and a shelled seed should be hard — too hard to dent with your fingernail and it splits, not squashes, when bitten. That means it is dry enough to store (below about 13% moisture — that is, very little water left in the seed).

For planting seed: store it in the pod. The whole, unbroken pod is the crop's own armour — weevils struggle to get through it. Keep it cool and dry.

For eating seed: shell it, then store the fully-dry seed in an airtight (hermetic) container — a sealed drum, or triple-layer PICS bags (bags with two inner plastic liners that you tie tightly to seal out the air). Sealed, airtight storage suffocates any weevils with no chemicals. A handful of clean, dry wood-ash mixed through the seed adds extra protection.

Check the store once a month for small round holes in the seed, fine powder, or live beetles.

If the seed still dents, bends, or feels soft or cool-damp, it is not dry enough — dry it more in the sun before storing, or it will mould and feed weevils. If you find weevils later, dry the seed again in hot sun and re-seal it airtight at once.