Soy is a grain vegetable that is still not widely grown in our gardens. However, it is the favorite food of vegetarians (it is used in the composition of tofu in particular) and this is justified: it is extremely rich in proteins, while being less caloric. In the garden, it also plays the role of green manure.
Of the wisteria family, soybeans or mung beans are a climbing annual plant from the Far East. It needs heat to grow, like the bean; it is cultivated in the same way. A legume, soybeans are a green fertilizer: they need little nutrients and enrich the soil with nitrogen.
The soybean reaches 3 ft high at maturity, its erect and rigid stem carries dense and reddish hairs. The flowers of this papilionaceous plant are white or purplish, they give place in summer to very hairy pods which finish their maturation in autumn. Each pod contains 3 to 4 round seeds, called soybeans.
Soybeans can be cooked like beans, the seeds can be eaten sprouted to garnish salads, cooked in purée, soup, vegetable pâté, or even in cakes. Soybeans have a taste similar to that of beans, with a touch of hazelnut.
Nutritionally, soybeans are rich in protein (soy flour provides twice as much protein as wheat flour, soy milk or juice is lower in calories than milk while providing as much protein), potassium, phosphorus, iron and B vitamins.
In which soil should soybeans be planted?
Plant soybeans in humus-rich, well-drained, predominantly sandy soil. The plot should be raked and well weeded before and during cultivation.
Under what exposure should soybeans be sown?
Soybeans need heat and sun.
When to plant soybeans?
Start its cultivation when more than 3 months of heat are assured. Heat is the key to success! In regions with a cool climate, start the seedlings in a warm pot. Transplant them outside when frosts are no longer a concern, as early as June.
How to plant soybeans?
In the vegetable garden, plant soybeans when the soil is warm, in May-June. This little known plant grows very well in our latitudes. Like beans, it needs a lot of heat and requires little water.
Start by working the soil with a hook to aerate it. Then make furrows a few cm deep, spaced 2 – 3 ft apart. Place a seed every 2 inches in the furrow, then cover with soil to close it.
Soybeans are harvested in late summer. Each pod produces several beans; dry them on trays and store them that way all winter.
Soybeans should not be grown on the same plot for 3 to 5 years. This legume enriches the soil with nitrogen, so grow leafy vegetables after it (lettuce, cabbage, spinach…) which will appreciate this richness. Soybeans do not have high nutrient requirements, so grow nutrient-rich vegetables before them: fruit vegetables and cucurbits (tomatoes, eggplant, squash, pumpkin, pumpkin…).
Cultivation and maintenance of soybeans
After emergence, continue to maintain the cleanliness of the soil by raking and weeding. This is to avoid the installation of undesirable weeds that could compete with the soybean plants.
Soybeans are not overly demanding in terms of water and, even if a more or less constant watering is ideal, they can tolerate short periods of drought… except at certain key moments:
- Water your plants generously during the flowering period.
- Also water generously when the pods are forming.
Once the plants have emerged, mulch them at the base to preserve soil moisture and control weed growth.
How to grow soybeans?
Soybeans are not only harvested from the pods, but from the whole plant. The pods, slightly hairy, are straight and pointed, difficult to shell by hand. They must be beaten in a bag in small quantities. For large quantities, it is advisable to use a special machine to clean the seeds. The seeds are light yellow, golden yellow or brown, but also green, black, sometimes spotted or marbled.
After about 3 months, the plants will start to turn yellow and lose their leaves. The pods will be ripe. When you shake a mature pod, you will hear the seeds, which have become smooth and detached inside, making noise. If you want to eat the pods fresh, you must pick them before they are ripe.
Choosing your soybean variety
The variety depends on the type of vegetable you want to harvest, but above all, you must choose a variety that suits our regions: early and adapted to our high latitude light cycle.
- Soybean ‘Summer Shell’: Japanese variety with green beans that can be eaten in whole pods.
- Soybean edamame ‘Green Shell’ : can be eaten green.
- Soybean ‘Fiskeby V’ : can be eaten as a grain, fresh or dry. It is a variety adapted to the coldest regions.
- Soybean edamame ‘Black Pearl’, mature in 86 days.
- Soybean ‘Envy’, consumed dry or semi-dry, it is a soybean mature in 75 days.
Diseases, pests and parasites
Soybeans can be attacked by aphids, slugs and seedling flies.
The seedling fly lays its eggs mainly in humid soils. A quick emergence of the plants – as soon as the primordial leaves (cotyledons) spread – is generally sufficient to prevent the presence of larvae (white maggots).
As for diseases, soybeans are sensitive to sclerotinia. To put all the chances on your side :
- Do not sow too early.
- Space your seedlings well. Spaced seedlings benefit from better aeration and respiration and dry more quickly. Humidity is a determining factor in the appearance of diseases.
- Choose a variety that is not very sensitive to sclerotinia and lodging.
- Space the watering turns, water less often but longer (which also prevents mildew).
Soybeans can also get downy mildew which causes small light yellow spots to appear on the foliage. Downy mildew refers to several diseases caused by the presence of microscopic fungi. The only effective treatment in organic farming is to remove the affected plants. Cut off all infected leaves and stems and burn them.