Short answer: Soya is one of the few crops that can fix much of its own nitrogen, provided the seed is inoculated with the right rhizobium and the field is not waterlogged or starved of phosphorus. Plant with the rains in rows about 50 centimetres apart, keep the crop weed-free for the first six weeks, and protect the flowering and pod-filling period from drought. Harvest when the pods are brown and rattle, and dry the grain well before you store it.
Key takeaways
- Inoculate the seed with the correct rhizobium on the day you plant, and keep the inoculant cool and out of the sun.
- Plant with the rains at about 50 centimetres between rows, and thin to a steady stand within the row.
- Keep the crop weed-free for the first six weeks, because soya loses ground quickly to weeds.
- Protect the crop from water stress at flowering and pod fill, and avoid waterlogged ground.
- Harvest when the pods are brown and dry, before they shatter, and dry the seed to a safe level for storage.
- Keep high-nitrogen fertiliser off soya, since it suppresses the nodules that fix the crop's own nitrogen.
A legume that leaves something behind in the field
A field that grew soya last season usually shows it. The maize that follows comes up greener, needs less top dressing and carries fewer weeds in its first month. Soya is a legume. Its roots carry small nodules where bacteria take nitrogen from the air and pass part of it to the plant. Some of that nitrogen stays in the soil when the crop is harvested, which is why a soya field is often the best preparation for the cereal that follows.
That benefit depends on doing the basics right. The bacteria must be present in the soil or added to the seed, the field must drain properly, and the crop must have the phosphorus and potassium it needs to make nodules and seed. A soya crop that is planted into a field with no suitable bacteria, or one that is waterlogged after a storm, will show pale leaves and poor pods, and the nitrogen benefit will not come through.
Halaal Farms is a day-old chicks hatchery and does not grow grain. We write about soya because many of the farmers who buy chicks from us are also looking at the protein side of their feed. The soya that goes into a broiler ration is often sourced from a processor, and some farmers want to understand the crop before they decide whether to grow some themselves.
The seasons and the soil soya needs
Soya grows best in the same seasons as maize, but it is more sensitive to both extremes of the rains. In the forest and transition zones, the major season is planted once the rains are reliable, usually from April to June. In the north, soya goes in with the first rains of May or June and must finish before the rains stop. The minor season in the south, planted in August or September, is possible but needs a variety that matures quickly, and the harvest must come in before the rains fail.
Choose a well-drained loam or sandy loam with a reasonable organic matter content. Soya does not tolerate standing water, and a field that floods after a storm will lose plants in a few days. The crop prefers soil that is near neutral in acidity, so a soil test is worth doing before you plant, because acid soils also limit the bacteria that fix nitrogen. Ask your district agricultural office or a college lab to check the pH and the main nutrients.
Do not plant soya on the same ground year after year. Rotate it with maize, cassava or a grass, which breaks the cycle of soil-borne disease and keeps the field from building a pest problem. Soya after maize is a common and sensible sequence, and our guide to growing maize in Ghana covers the cereal side of that rotation.
Varieties, seed and the inoculant that makes the nodules
Soya varieties differ in how long they take to mature, how tall they grow and how well they handle disease and dry spells. Ghana has public varieties from the research institutes, and the list of recommended varieties changes over time. Ask CSIR-SARI in the north or the Crops Research Institute in the south which varieties are recommended for your zone, and whether they are sold as certified seed in your area. Early-maturing types suit the minor season and the short northern window. Medium-maturing types suit the major season in the forest belt.
| Item | What to do | Why it matters |
|---|---|---|
| Seed source | Buy certified seed from a reliable dealer or research station | Germination and purity decide the stand you get |
| Germination test | Place a sample on damp cloth for several days and count the sprouts | Lets you replace weak seed before planting |
| Inoculant | Use a soya-specific rhizobium inoculant, applied to the seed before planting | Gives the bacteria a start where the soil has none |
| Seed rate | Check your variety's recommendation, commonly around 60 to 80 kilograms per hectare | Too thin a stand loses yield, and too thick a stand competes |
Inoculation is cheap insurance for the field. Mix the inoculant with the seed in a shaded place, using the amount on the packet and a little water or sugar solution to make it stick. Plant the treated seed the same day, because the bacteria die in heat and sun. Do not mix the inoculated seed with fertiliser, lime or pesticide, which can kill the bacteria. If the field has grown soya recently, the soil may already carry the right bacteria, but a fresh inoculant is still worth using when you are in doubt.
Planting: rows, depth and the stand you are aiming for
Plant soya in rows about 50 centimetres apart. Within the row, aim for seeds about 5 to 10 centimetres apart, with two or three seeds in each spot, thinned to a single plant later if the stand is too thick. Plant about 3 to 5 centimetres deep, into moist soil. A seed that goes in too deep will struggle to push through the crust, and one left on the surface will be eaten by birds or dry out.
The aim is an even stand. Gaps in the row let the weeds in, and clumps of plants compete with each other for light and water. Mark the rows with a line or a stick and check the spacing with a short measuring cord. Farmers who plant by eye often end up with a field that looks full from the road and thin from the middle.
Plant when the soil has taken in a good rain and the forecast looks steady. Planting too early into dry soil is a common mistake, because the seed sits without moisture and the stand comes up patchy. Planting too late means the pods fill when the rains are fading, and the yield suffers.
Fertiliser: phosphorus and potassium, and the nitrogen trap
Soya fixes its own nitrogen, so the most common fertiliser mistake is to add nitrogen the crop does not need. High nitrogen in the early weeks encourages leafy growth and suppresses the nodules, and the plant then relies on the nitrogen in the fertiliser instead of its own bacteria. A small starter dose can be used on very poor ground, but the rule is to follow your soil test and extension advice rather than a standard top dressing like the one used for maize.
Phosphorus is the nutrient soya most often lacks in Ghanaian soils. It drives root development, nodule formation and pod filling. Potassium matters too, especially on sandy soils that have been cropped hard. Your soil test tells you whether these are short, and the district office can advise on the form and rate. Apply the phosphorus at planting, placed in or beside the seed row, and keep it away from the inoculated seed.
Poultry manure, composted first, can supply some phosphorus and organic matter, as our guide on using poultry manure as a fertiliser explains. Lime may be needed on acid soils, but it should be applied well before planting and based on a test. Do not guess at lime rates from one field to the next, because too much lime can lock up other nutrients.
Weeding: the first six weeks, when soya loses the race
Soya is a poor competitor in its early weeks. The seedlings are small and slow to cover the ground, and weeds that come up with them can take much of the water and light. Most of the yield loss from weeds is set in the first six weeks, so the weeding programme should be built around that window. Weed once at two to three weeks after emergence, and again at about five or six weeks, before the canopy closes over the rows.
Hand weeding and hoeing work well on small plots, and a row weeder or animal-drawn cultivator is faster on larger ones. Take care when you cultivate close to the plants, because the roots are shallow and easy to damage. Some farmers use a pre-emergence or early post-emergence herbicide. If you do, choose a product that is registered for soya, follow the label, and keep the spray off the neighbouring fields and the water. Ask your extension officer before you buy.
Intercropping soya with maize is common in some areas, and it spreads the risk. The soya yield is usually lower in a mixed field than in a pure stand, so decide which crop you want to protect, and set the spacing and the weeding to suit that choice.
Pests and diseases to scout for every week
Soya is attacked by several insects and by a number of diseases, and the timing of the attack matters. Pod-boring caterpillars, including the legume pod borer, feed inside the pods and can take a large share of the seed. Aphids cluster on young shoots and sap the plant. Leaf-feeding beetles and grasshoppers strip the leaves, and in dry weather they can do real damage before the pods form. Walk the field weekly, check the underside of the leaves and open a sample of pods to look for holes and larvae.
Rust is one of the most serious diseases of soya, and it is a risk in parts of West Africa. It shows as small brown or reddish spots on the underside of the leaves, which can cause early leaf drop. Bacterial and fungal leaf spots show up in wet weather, and they spread faster in dense stands. Good spacing, clean seed, rotation and resistant varieties all reduce the risk.
When you find an attack, take a sample to your extension officer or MoFA plant health staff for identification before you decide what to do. Spray only what the scouting shows is needed, follow the product label, and respect the waiting period before harvest. A field that is scouted weekly needs fewer sprays than one that is sprayed on a calendar.
The flowering and pod-filling window, when water matters most
Water matters most during flowering and while the pods fill. A dry spell at this stage can cause flowers to drop and pods to abort, and the yield can fall sharply even if the crop looked healthy a month earlier. Waterlogging is just as damaging, because the roots need air, and a field that stays wet for several days can lose plants and yield quickly. The trick is to keep the crop in the middle of the moisture range during these weeks.
Mulching the rows with dry grass or crop residue helps the soil keep its moisture during a short dry spell. Keeping the crop weed-free means the water in the soil is for the soya rather than for the weeds. Drainage furrows along the low edges of the field move excess water off the rows after heavy rain.
Keep a note of the rainfall in the weeks around flowering, and compare the record with the state of the field when you walk it. That record is the best guide to what happened and what to change for the next season.
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Harvest: when the pods turn brown and start to rattle
Soya is ready when most of the leaves have dropped, the pods have turned brown and the seeds rattle inside them when shaken. The crop matures over a period, so waiting for every pod to be ready leaves the earliest ones to shatter in the field. Plan the harvest for a day or two when most of the pods are dry, and cut or pull the plants early in the morning when the pods are less brittle.
Pods shatter easily in hot, dry weather, and the seeds fall onto the ground before you can collect them. Harvest in the cooler part of the day, handle the plants gently, and spread them on a clean tarpaulin or a raised floor to finish drying. Thresh by beating the plants or by walking the stems on the tarpaulin, then winnow the grain to remove the chaff and the broken pods.
Dry the seed to a safe moisture level before you store it. Soya stored damp will heat and mould quickly, and the quality falls. Spread the grain thinly in the sun for a few days, turning it, until the seed feels dry and firm when pressed. Store it in clean sacks off the floor, in a dry room, and check it every few weeks.
Processing and where the soya goes on a mixed farm
Soya grain has several destinations. Some farmers sell it to processors or local traders for food, and some keep it for home use as roasted beans, soy milk or other foods. The grain can also be processed into meal, and meal is one of the richest protein sources in a poultry ration. The processing step matters, because raw soya contains anti-nutritional factors that must be removed before the meal is fed to birds. Our guide to soya and groundnut cake for poultry explains how the cake is processed and tested, and why the testing matters.
The haulm is a second product. Soya leaves and stems have some feed value, and they can be cut and dried for animals in the dry season, but they are not a substitute for the grain and need to be dried well to avoid mould. For the dry-season feed plan that uses this kind of residue, see our guide to pasture and grazing management in Ghana. Our piece on protein sources for poultry feed in Ghana compares soya with the other options a farmer can use.
If you grow soya to feed your own birds, weigh the grain, keep a record of how much you process and feed, and watch the flock's growth and laying. A simple feed record shows whether the home-grown protein is performing as expected.
The break-even sum before you plant
The soya budget is a simple sum with several variables, and each one should come from a local source. Start with the area you plan to plant. Estimate the yield from the variety's recommended figure in your zone and from your own records, and be cautious with the estimate for your first season. Multiply the yield by the price you expect to get at harvest, using current rates from the market or the buyer, not last year's figure. Then subtract the costs.
The costs are seed, inoculant, fertiliser, weeding labour or herbicide, crop protection, land preparation, harvest labour, drying space, sacks and transport. Get each of these from a local supplier or hire operator, and write the source and the date next to the figure. The result is your margin per hectare. If the margin is small or negative at the low end of the price range, change the variety, reduce the area or find a buyer before you plant.
Do not forget the benefit to the next crop. A soya field often gives the following maize crop a boost in nitrogen, and that saving is real money, even if it does not show up in the soya sum. Record it when you can see it in the field.
A checklist for the soya season
Use the list below from the first week of land preparation to the last sack in the store. Each step is simple, and missing one is usually what separates a good soya field from a disappointing one.
- Test the soil for pH, phosphorus and potassium, and agree the plan with your extension officer.
- Choose a variety recommended for your zone, and buy certified seed from a reliable source.
- Test the germination of a seed sample and replace weak seed before planting.
- Inoculate the seed on the day of planting, in shade, and keep it away from fertiliser.
- Plant into moist soil at about 50 centimetres between rows, 3 to 5 centimetres deep.
- Weed at two to three weeks and again at about five to six weeks.
- Scout the field weekly for pod borers, aphids, beetles and rust.
- Watch the rainfall at flowering and pod fill, and keep drainage clear.
- Harvest when the pods are brown and rattle, in the cooler part of the day.
- Dry the seed to a safe level, and store it in clean, dry sacks off the floor.
Write each step in a field book with the date. That book becomes the record you use to plan the next season, and it will tell you which step needs attention first.
Where soya meets the poultry side of the farm
Halaal Farms supplies day-old chicks, fertile eggs, table eggs and grown birds. We do not supply soya, seed or the grain that goes into a ration, and we do not sell feed. We write about soya because protein is the biggest question many poultry keepers face, and a farmer who understands the crop is in a better position to talk to a feed miller or to decide whether a home-grown supply is worth the effort.
If you are starting a flock, the chicks come first. Our day-old chicks in Ghana page explains the breeds we hatch, and you can order through the order section or WhatsApp us on +233 24 915 1503 with your region and the number of birds. Once the birds are on the ground, the basics of poultry feed formulation explain how protein fits with energy and minerals in the ration, and integrating poultry with crops and fish shows how the farm pieces can fit together. If you are planning a larger mixed project, our partner page sets out how we work with farmers.
For the crop, your MoFA extension officer and the research institutes are the right people to ask. We can help with the chicks, and they can help with the soya field.
Questions farmers ask
Do I need to inoculate soya seed in Ghana?
In most cases, yes, especially on fields that have not grown soya recently. The inoculant provides the right rhizobium bacteria to form nodules and fix nitrogen. Use a soya-specific product, apply it to the seed in shade on the day you plant, and do not mix it with fertiliser or pesticide, which can kill the bacteria.
When should I plant soya in Ghana?
In the forest and transition zones, plant with the major-season rains from about April to June, once the soil is wet and the rains look steady. In the north, plant with the first rains of May or June. The minor season in the south is possible with a fast-maturing variety, planted in August or September. Check the variety's maturity against the rains.
Does soya need nitrogen fertiliser?
Usually not. Soya makes its own nitrogen through its nodules, and high nitrogen fertiliser suppresses nodulation. A soil test will show whether phosphorus and potassium are short, and those are the nutrients most often needed. Follow your extension officer's advice on any starter dose for very poor soil.
How do I stop weeds from taking my soya yield?
Weed twice, at about two to three weeks and again at five to six weeks after emergence, to keep the rows clear during the critical period. A registered herbicide for soya can help, if it is applied to the label and checked with your extension officer. Mulching and a weed-free start also reduce the labour.
What causes soya pods to fall off?
Dry spells during flowering and pod filling are a common cause, as are waterlogging and pod-boring insects. Waterlogging damages the roots and can stop pods filling. Walk the field and open a few pods to check for holes and larvae. Keep the rainfall record and the scouting record together so you can see what happened.
When is soya ready to harvest?
Harvest when most of the leaves have dropped, the pods are brown and the seeds rattle when shaken. Pick the day when most pods are dry, and cut or pull in the cool of the morning to reduce shattering. Dry the threshed seed thoroughly before you store it, because damp soya heats and moulds quickly.
Can I feed soya straight to my birds?
Raw soya contains anti-nutritional factors that must be removed by proper processing before it is fed to poultry. Processed soya meal is a common protein source, but its quality should be checked, and the amounts should be set by a feed formulator who knows your flock. Our guide to soya and groundnut cake explains the testing steps.
