How to grow green gram

Plan this in the weeks before you sow — as early as two months out, and settle it at least a week before sowing, while you can still choose the field and order the seed.

Choose a field that grew a cereal last season — maize, sorghum or millet — not beans, cowpeas or groundnuts. Rotating this way breaks the cycle of root diseases and soil pests that build up under beans.

Where the yellow mosaic virus is known in your area (plants that go bright yellow and stunted — see the scouting task), choose a virus-resistant or tolerant variety. Ask your dealer or extension officer for one by name.

Pick a well-drained spot. Green gram hates wet feet — it rots and yellows in low ground that stays soggy after rain.

Aim the crop at the short rains or a slot right after your cereal harvest — the fast 60–90-day crop fits neatly into either.

Buy certified seed — a sealed, labelled bag from a registered dealer, with the variety name and this season's packing date — not grain scooped from a sack, which may be old, mixed or diseased.

Ask for a virus-resistant or tolerant variety where the yellow mosaic virus is a problem. Keep the label and receipt in case the seed grows poorly.

Buy a sachet of rhizobium inoculant — a cheap powder of helpful root bacteria (Bradyrhizobium) that lets green gram pull its own nitrogen from the air. Buy the type made for green gram / mung bean, check it is not past its expiry date, and keep it cool and out of the sun — heat kills the bacteria.

Buy a little phosphorus starter — a small amount of DAP (di-ammonium phosphate, a starter fertiliser) or single superphosphate. Green gram is a bean: it feeds itself with nitrogen, so it needs almost no nitrogen fertiliser — just phosphorus to build strong early roots. Your recommendation gives the amount for your field.

Store seed, inoculant and fertiliser dry, off the floor, and away from food, water and children, and use the inoculant before its expiry date.

In the two weeks before sowing, clear weeds and old crop trash off the planting lines so weeds don't get a head start.

Loosen the soil to about a hand-span deep (≈20 cm) so roots go down and rain soaks in, then break the clods to a fine, crumbly tilth — small seed sown into big clods sits in air pockets and comes up patchy.

Keep off low, waterlogging-prone ground. If your only field holds water, make raised beds or ridges and plant on top, so the roots stay above the wet.

Level the surface so water doesn't pool. On a slope, work across the slope (not up-and-down) to catch and hold the rain.

Sow on a good planting rain into warm, moist soil, so the seed comes up fast and even in 3–7 days. Push your hand in — the soil should be wet below the surface, not just damp on top.

On land that has not grown green gram or beans before, coat the seed with the rhizobium inoculant first: moisten the seed with a little clean water or thin sugar-water, dust the powder over it in the shade until the seed looks dark, and sow within a couple of hours. This gives the plant its own nitrogen supply — keep the coated seed out of the sun.

Open furrows just under two hand-spans apart (≈37 cm) — narrow rows, so the crop shades out weeds fast.

Space the seed about half a hand-span apart (≈10 cm) down the row, and cover it about one finger-joint deep (3–5 cm) — a touch deeper in dry, sandy soil, shallower in heavy, wet soil.

Band the little phosphorus starter (DAP) about a finger-joint (3–5 cm) to the side of the seed and slightly below it — never touching the seed, or the fertiliser burns and kills the sprout. Remember: as a bean, it wants phosphorus, not nitrogen.

Cover and firm the soil so each seed sits snugly in moist earth, aiming for a seed rate of about 12–20 kg per hectare.

From about 5 days after sowing, walk the crop twice a week — cover the corners and the middle, not just the edge by the path.

Whitefly: turn leaves and look at the undersides for tiny white moth-like flies that lift off in a cloud when you shake the plant. These are the ones that carry the virus.

Yellow mosaic virus (MYMV, short for mungbean yellow mosaic virus): look for young leaves with bright yellow-and-green patches (mottling), puckered, on plants that stay small. Pull out and destroy any mottled plant the moment you see it — this is called roguing, and it removes a source the whiteflies would spread to the rest.

Cutworms: look for young seedlings cut clean off at ground level (worst in the morning). Scratch the soil nearby to find the fat, grey, curled caterpillar and squash it.

Count the gaps (stations with no plant) as you go, so you know whether to fill them while the crop is still only a few days old.

If you irrigate, keep the topsoil moist but never waterlogged from sowing through the first 10 days — green gram rots in standing water.

Water every 3–5 days, more often on sandy soil and in heat; check by pushing a finger in, and water when the top few centimetres are dry.

Water gently, so you don't wash out seed or beat the soil into a hard crust the seedlings can't push through.

Keep walking the crop twice a week, from about 10 days after sowing on.

Whitefly and virus: turn leaves for whiteflies on the undersides, and pull out any plant showing bright yellow-and-green mottling — rogue it straight away, roots and all.

Aphids: look for clusters of tiny soft green or black insects on the growing tips and leaf undersides, often with sticky, shiny leaves and ants running about. A few are normal; dense colonies curling the tips need action.

While you are in the crop, judge how weedy it is — this is the critical weeding window, so if weeds are coming, weed now (see the weeding task).

Weed the crop clean between 15 and 35 days after sowing — the earlier in that window, the better, before the weeds get bigger than the crop.

Hoe shallowly between and within the rows — green gram roots run near the surface, and deep hoeing close to the plants cuts them and the nitrogen-fixing nodules on them (the little pinkish knobs on the roots where the root bacteria make the plant's own nitrogen).

Pull weeds close to the plants by hand so you don't disturb the crop, and take them roots and all where you can — chopping only the tops lets many regrow.

The narrow rows (≈37 cm) work for you: once green gram closes its canopy and shades the ground, new weeds struggle — so your job is just to keep it clean until it covers over.

In dry areas, leave the pulled weeds lying between the rows as a mulch to hold moisture.

If you irrigate, water every 7–10 days during dry spells through leafy growth (about 10 to 30 days after sowing).

Let the surface dry a little between waterings — green gram would far rather be a bit dry than waterlogged.

Don't let the crop wilt badly at this stage; a stunted frame carries fewer pods.

From about 30 days after sowing, when flower buds appear, scout every 2–3 days — flowering is short and these pests move fast.

Thrips: open a few buds and flowers and look for tiny, thin, fast-moving slivers (yellow to black) inside; damaged flowers dry up and drop without setting a pod. Tap a flower over your pale palm to see them move.

Maruca pod borer: look for flowers and young pods webbed together with silk, with droppings caught in the webbing; pull the web apart and you'll find a caterpillar feeding inside.

Keep turning leaves for whitefly, and rogue any late yellow-mottled virus plants you still find.

If you find thrips or Maruca webbing in the flowers, spray at bud / 50% flowering (see the flowering-spray task) — that is the moment they are out in the open.

Spray at first flowers / 50% flowering — not before the buds show, and not after the pods have formed and the caterpillars are already inside.

Measure the approved product with its own cap into a full knapsack sprayer (15–20 litres) exactly as the label says — don't guess or over-mix.

Cover your skin, eyes, nose and mouth, and spray in the cool of early morning or evening with the wind behind you, so the mist blows away from your face. Wet the flowers and the leaf undersides until just before it drips.

Where the pests keep coming, spray again about 10 days later, and rotate to a different chemical group so the pests don't get used to one.

Respect the pre-harvest interval — the number of days the label says to wait after spraying before it is safe to pick and eat. Wash yourself and the sprayer afterwards, well away from wells, rivers and food.

From about 30 days after sowing, through flowering, keep the soil evenly moist — water every 5–7 days, more often in heat.

Never let the crop wilt during flowering, even for a day — wilted plants shed their flowers and set fewer pods.

Water in the cool of the day to lose less to evaporation, and keep it even — big swings from bone-dry to flooded knock the flowers off.

From about 45 days after sowing, check the pods twice a week as they form and fill.

Pod borer (Maruca): look for pods webbed together, small bore-holes with droppings at the entry, and hollowed or eaten seeds inside when you split a pod open.

Pod-sucking bugs: look for green, brown or spiny shield-shaped bugs sitting on the pods; the seeds beneath their feeding spots turn sunken, dark and shrivelled.

Pull and open a few suspect pods to judge how many are hit — light numbers you can tolerate, but heavy attack on filling pods needs a spray (same care as the flowering spray).

If you irrigate, keep the soil moist through pod-fill (about 45 to 65 days after sowing), watering every 5–7 days.

Keep the water even while the pods and leaves are still green and filling.

As the first pods turn black or brown and dry, start to ease off the water so the crop can dry down for picking — don't keep it wet into ripening.

Start the first pick from about 60 days after sowing, as soon as the earliest pods are black or brown, dry and hard. Pick in the cool of the morning, when dry pods are less likely to burst as you handle them.

Take only the fully dry, dark, rattling pods each pass — leave the green and part-filled ones on the plant to ripen for the next round.

Come back about every 7 days for a second and, if needed, a third pass, until you have gathered the last of the pods.

Readiness check: a ready pod is black or brown, dry, and rattles when shaken, with hard seed. If the pods are still green or leathery and the seed is soft → they are not ready; leave them and pick them in the next pass — soft seed shrivels and won't store.

Carry the picked pods in to dry further before threshing — don't leave them heaped in the sun to overheat.

Let the picked pods dry fully first — in the sun on a mat, tarpaulin or clean hard floor, never on bare earth, which pushes damp back in and adds stones and dirt.

Put the dry pods in a sack or on a tarpaulin and beat or tread them gently to split the pods and free the seed — don't pound so hard you crack the grain.

Winnow the seed: pour it slowly in a light wind or in front of a fan so the chaff and dry pod-bits blow away and the clean, heavy seed drops.

Pick out any stones, trash and holed or broken seeds — clean, whole seed stores far better.

Dry the threshed seed hard on a mat, rack or tarpaulin (never bare ground), turning it so it dries evenly and covering it if rain threatens.

Moisture check — bite test: seed dry enough to store is hard and shatters when you bite it, not squashy or dented. That's about ≤12% moisture — roughly one part water in eight. If it squashes or dents → it is still too wet; dry it more before you seal it, or it will mould and heat in the bag.

For extra protection, sun-disinfest first: spread the dry seed thin in strong sun for a few hours, or seal it in a clear plastic bag or bottle in full sun — the heat kills eggs and beetles already in the seed.

Seal the fully-dry seed in a hermetic (airtight) bag — a PICS or triple-layer 'grain-saver' bag — pressing out the air and tying each liner tightly. The airtight seal suffocates the bruchid; no chemical needed.

Keep the sealed bags off the floor and away from the wall, in a cool, dry, shaded place, and try not to open them often. Check monthly for round exit-holes, fine powder or moving beetles, and re-dry and re-seal if you find any damp.