Growing Soybeans

Like corn and some other crops of long domestication, the relationship of the modern soybean to wild-growing species can no longer be traced with any degree of certainty. It is a cultural variety (a cultigen) with a very large number of cultivars. However, it is known that the progenitor of the modern soybean was a vine-like plant, that grew prone on the ground.

Beans are classed as pulses whereas soybeans are classed as oilseeds. The word soy is derived from the Japanese word shoyu (soy sauce/soya sauce).

Soybeans today are a staple food for many people. Vegetarians rely on them often for protein in place of meat or fish. Baby formula for those infants who are lactose intolerant is made of soybeans. Most people buy their soybeans or soybean products at the grocery store, but they can be grown easily at home.

Ideal soil for peak soybean production is a loose, well-drained loam. The soil and cultural requirements and methods of growing soybeans are essentially the same as for bush forms of common beans. Soybeans, however, are slower growing than most garden beans, requiring 3 to 5 months for maturity, and warmer weather.

The advantages of loose, well-aerated soil with adequate humus and abundant living organisms include the following:

• Loose, aerated soil allows air to get to roots and nitrogen-fixingroot nodules, plus it soaks up rain and lessens erosion, and it discourages many of the worst weeds.
• Humus and soil organisms provide steady, balanced nutrition to roots, soak up and hold moisture (provide "droughtproofing"), and protect roots from harmful nematodes, insects and disease pathogens.
• Organic matter also tends to buffer soil from extremes in pH (acidity and alkalinity).

Use good quality seed of high germination rate (80 to 90% or more). If soybeans have not been grown on that soil for three to five years, it is best to inoculate the seed with the proper strain of nitrogen-fixing bacteria (Rhizobium). Some strains are more effective nitrogen fixers than others. The bacterial inoculant can be applied to the seed just before planting time or in the row during planting (the latter requires soil inoculant).

To achieve a desired population, you need to calculate the number of seeds required. Some seeds will not germinate, and some that germinate will not become established because of weather, pests or disease. Generally, if the seedbed and planter are good, about 90 to 95% of germinated seedlings will become established.

After being planted in the soil, the seed absorbs moisture, changing from less than 13% moisture to about 50% in several hours. After one or two days the first root (called the radicle) emerges through the seed coat and begins growing downward to establish the root system.

You need to plant 7.9 seeds per foot of row to get six plants per foot. Row width should be between 12 to 18 inches (30 to 45 cm). Since soybean seed is usually sold by weight rather than by number of seeds, you -need to know the number of seeds per pound to figure pounds needed per acre. If the seed dealer cannot give you number of seeds per pound, weigh a few one-ounce samples on a postage scale to get an average figure.

Seed germination and emergence is a critical period in the life of a soybean because poor emergence due to a soil crust from cold temperatures or seedling pests and diseases can drastically cut yield. After emergence for the first six to eight weeks the soybean grows its stem (and possibly branches) and leaves. This is called the vegetative period.

Seeds should be planted deep enough to absorb enough moisture to germinate, but not so deep that they have trouble emerging from the soil. Some varieties can emerge from greater depths than others. Typical planting depths are I to 1 l/: inches, but if soil is low in moisture or sandy plant 2 inches deep. In cool, moist soil, seed can be planted 1 inch deep if there is no danger from herbicide.

Best results are obtained using a unit planter or grain drill to plant in rows. Drills usually do not handle rough seedbeds as well as planters. Broadcasting or aerial seeding followed by light tillage to cover seed often results in uneven emergence and stands that are too thin in some areas and too thick in others.

The young roots start to develop root nodules within a week after emergence if the proper nitrogen-fixing bacteria are present in the soil. The nitrogen fixing nodule bacteria, technically called Rhizobium enter the nodules and after ten to fourteen days are able to supply most of the plant's nitrogen needs, if the nodules are healthy. In favorable soil conditions a couple dozen or so pea-sized nodules will develop on the upper roots of a plant. Healthy nodules will be pink or reddish inside.

They also are taller growing, the larger, later varieties requiring a greater distance between rows than dwarf snap beans. Small, early varieties may be planted in rows as close as 2 feet (60cm), but the larger, later ones require 3 feet (1m) between rows.

Differences in time of development among varieties are so great that the gardener must choose the proper variety and know its time of maturity in making plans for planting in any particular locality.

In cooler sections the rate of development will be slower. Only the early varieties should be grown in more Northerly climates, and the medium or late varieties in the South. Plantings should be made principally when tomatoes and other long-season, warm-weather crops are put in the garden.

Most people grow soybeans in a crop rotation sequence, typically with a non-legume such as corn, small grains, sorghum or cotton. The yield of the non-legume is improved because of the left over nitrogen from the soybean root nodules. Also, disease, pest and weed problems are reduced in rotations compared to growing one crop continuously. These disadvantages can be overcome if soil is in peak fertility and condition.

Soybeans are also often grown in a double-cropping system, with two crops being grown in the same year. Winter wheat followed by soybeans is the most common; snapbeans or peas followed by soybeans is another. Timing is critical in more northerly areas.

For use as a green vegetable, soybean pods should be harvested when the seeds are fully grown but before the pods turn yellow. Most varieties produce beans in usable condition over a period of a week to 10 days. The green beans are difficult to remove from the pods unless the pods are boiled or steamed 4 to 5 minutes, after which they are easily shelled.

The yields per unit area of land are about the same as are usually obtained with peas and are thus less than can be obtained with many other vegetables. On this account, they appear of major interest only to gardeners having medium to large gardens.

Once flowers appear, and then soybeans begin to form, the plants are almost ready to harvest. When the pods are two inches  (5 cm) or so, they are ready to harvest. Open one pod to make sure that the seeds are cream-colored, not green, indicating that they are ready for harvest. The seeds will be ready for anything – cooking, etc. Steamed soybeans are a delicious vegetable addition to almost any main course.

Use soybeans in place of eggs in order to hold cakes and breads together (tofu is sometimes used as an emulsifier, which is made from soybeans). Try out their many uses.