How to grow soybean
Overview
Soybean (Glycine max) is a warm-season legume grown for its tender green pods (edamame) or protein-rich dried seeds. Home gardeners benefit from regular picking, which encourages continued pod production throughout the growing season.
Varieties
- Envy — Early maturing edamame variety with excellent flavour, popular in Australian home gardens.
- Chiba Green — High-yielding edamame with large, sweet pods, well suited to temperate and subtropical zones.
- Hooks — Reliable variety for dry soybean production, good for processing into tofu or miso.
Soil Preparation
Prefers well-drained, loamy soil with pH 6.0–7.0. Incorporate compost before planting to boost organic matter. Avoid heavy clay or waterlogged conditions; raised beds can improve drainage if needed.
Growing Guide
Sow seeds directly into warm soil (above 15°C) after all frost danger. Space seeds 5–7 cm apart in rows 45–60 cm apart, thinning to 10–15 cm apart; plant 2–3 cm deep. Ensure full sun and steady moisture, especially during flowering and pod fill. Use drip irrigation or water at soil level to avoid fungal diseases. For best results, push growth early by providing warmth and consistent care.
Sowing
Direct sow only; soybeans do not transplant well. Sow seeds 2–3 cm deep, 5–7 cm apart after soil reaches 15°C. Germination takes 5–10 days. Inoculate seeds with appropriate rhizobia bacteria if not already present in the soil.
Care
Apply a low-nitrogen fertiliser (e.g., 0-10-10) at planting and again when pods begin to form. No pruning is needed, but light staking may help if plants become top-heavy or in windy areas. Mulch to retain moisture and suppress weeds.
Companion Planting
Soybean partners well with corn, squash, cucumbers, potatoes, and strawberries in a three-sisters style or interplanting. Avoid alliums (onions, garlic) as they can stunt growth. The nitrogen-fixing roots also benefit heavy-feeding neighbours.
Common Pests & Risks
Common pests include aphids, two-spotted mites, and green vegetable bugs. Control aphids with insecticidal soap or neem oil; encourage beneficial insects like ladybirds. Avoid overhead watering to reduce downy mildew and other fungal diseases. Crop rotation helps prevent soil-borne issues.
Harvesting
Harvest green pods for edamame when they are bright green and plump, typically 10–12 weeks after sowing. For dry beans, allow pods to dry on the plant until brown and brittle, then shell. Pick regularly to encourage more pod set.
In the Kitchen
Edamame: blanch unshelled pods in salted boiling water for 5 minutes, then serve with salt or in stir-fries. Dried beans require soaking and thorough boiling before use in soups, stews, or homemade tofu. Store green pods in the fridge for up to a week, or blanch and freeze for longer storage.
Troubleshooting
Yellow leaves: often iron deficiency in alkaline soil; lower pH or apply iron chelate. Stunted growth: cold soil or poor drainage; wait for warmer weather. Pods not filling: heat stress or inconsistent watering; maintain steady moisture. Spots on leaves: downy mildew; improve air circulation and avoid overhead watering. Poor germination: soil too cold or too wet; wait for optimal conditions.