Soybean
Glycine max
About Soybean
Soybean is the world's most important oilseed crop, providing high-quality protein (40%) and oil (20%). Global production exceeds 370 million tonnes annually, with Brazil, the United States, and Argentina producing 80% of the total. Soybean meal is the dominant protein source in animal feed worldwide. The crop fixes atmospheric nitrogen through symbiosis with Bradyrhizobium japonicum bacteria, making it excellent in rotation with cereals. In sub-Saharan Africa, soybean production is expanding rapidly as a protein source and soil improvement crop. Soybean is also a key ingredient in food products including tofu, tempeh, soy sauce, and soy milk.
Growing Conditions
Full sun — short day plant, flowering triggered by day length (variety-dependent)
450-700 mm per crop. Most critical at flowering through early pod fill (R1-R5).
Well-drained loam. pH 6.0-7.0. Inoculate with Bradyrhizobium if first time planting soybean in a field.
Optimal 25-30°C. Cool temperatures (<15°C) delay emergence and maturity.
Moderate. High humidity promotes soybean rust and foliar diseases.
Warm season — 80-150 days depending on maturity group and latitude.
Step-by-Step Growing Tips
Inoculate seed with Bradyrhizobium japonicum if planting in new soybean fields
Select maturity group appropriate for your latitude
Plant at 45-60 cm row spacing, 300,000-400,000 plants/ha
Monitor for soybean rust from R1 (flowering) and apply preventive fungicide if detected regionally
Harvest when 95% of pods are brown and seed moisture is 13-15%
Rotate with cereals (maize, wheat) for disease break and nitrogen credit
Disease Risks to Watch
All diseases →Asian soybean rust (Phakopsora pachyrhizi) causes tan to dark brown pustules on leaf undersides, leading to rapid defoliation and 10-80% yield loss. No durable resistance exists. Manage with preventive fungicide applications (triazole + strobilurin) at R1-R2 stage, early planting, monitoring sentinel plots, and observing the vazio sanitário (soybean-free period) in Brazil.
Soybean mosaic virus (SMV) causes light and dark green mosaic mottling, leaf crinkling, stunting, and seed coat mottling. It is seed-transmitted (up to 5%) and spread by aphids. Manage by planting certified virus-free seed, using resistant varieties (Rsv genes), controlling aphids, and roguing infected plants early in the season.
Downy mildew produces angular yellow patches on upper leaf surfaces with grayish-purple fuzzy growth underneath. Caused by Peronospora or Plasmopara oomycetes, it thrives in cool wet weather. Manage with resistant varieties, preventive mancozeb or copper sprays, good air circulation, and avoiding overhead irrigation. It requires free water to infect — keep leaves dry.
Companion Planting
✅ Good Companions
❌ Avoid Nearby
Growing Zones
Frequently Asked Questions
When is the best time to plant Soybean?
Warm season — 80-150 days depending on maturity group and latitude.
What soil does Soybean need?
Well-drained loam. pH 6.0-7.0. Inoculate with Bradyrhizobium if first time planting soybean in a field.
How much water does Soybean need?
450-700 mm per crop. Most critical at flowering through early pod fill (R1-R5).
What are the most common diseases affecting Soybean?
The most common diseases are: soybean rust, soybean mosaic virus, downy mildew. Monitor regularly and practice crop rotation.
What plants grow well with Soybean?
Good companions include: maize. Avoid planting near onion, garlic.
Related Crops — Fabaceae
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