Soybean Guide

Propagation

Soybean is propagated directly from seed. If seeds are planted in a field where soybean has not been grown in the 3–5 year previous, they should first be inoculated with nitrogen fixing bacteria. The seedbed should be prepared prior to planting by removing any crop residue, weeds and large stones. Tilling the soil helps to break up large clods of earth. Seeds may be sown mechanically or by hand. In tilled soils, seeds are usually planted at a depth 3.2–4.5 cm (1.25 to 1.75 inch) in rows spaced 30 cm (11.8 inch) apart. Alternatively, no-till planting may be used to plant seeds in the stubble of a previous crop without first cultivating the soil. With this method, seeds are drilled into the soil in rows spaced 17.8 cm (7 inch) apart. No-till practices reduce soil erosion and reduce the loss of moisture in the soil.

General care and maintenance

Weeds are often a problem in soybean fields and can be reduced through good preparation of the seedbed and maintaining a weed-free seedbed for several weeks prior to planting. Weeds may be controlled with appropriate herbicides, where available, or through mechanical cultivation where necessary. Soybeans should be provided with irrigation at flowering and again at seed-set for maximum seed fill and optimal yield. Irrigation should be increased in sandy soils that do not retain as much moisture. Soybeans fix approximately half of the nitrogen they require for growth and the other half must be supplied from the soil or through fertilizer application. Soybean also requires an adequate supply of phosphorus and potassium and application rates should be based on the results of a soil test.

Harvesting

Soybeans are ready to harvest between 70 and 160 days after planting, depending on variety. Plants are ready for harvest when the leaves and stems have turned yellow and the seed pods brown to black. Soybeans for fresh use are cut while still green. Plants may be pulled by hand or cut with the use of a combine. Once cut, the seeds are removed from the pods by threshing.

Soybeans belong to the pea family. Soybeans come in many colors, including:

• Green soybeans: Young green soybeans are also called edamame. People can steam and eat out of the pod as an appetizer. Shelled edamame is also available in salads, stir-fries, and soups.
• Yellow soybeans: Producers typically use yellow soybeans to make soy milk, tofu, tempeh, and tamari and this could also play a role in the production of soy flour for baking.
• Black soybeans: Several Asian food cultures use simmered or fermented black soybeans in traditional dishes.

Soy foods come in dozens of forms. Some types of soy are used as ingredients in commercially produced food products, and other kinds of soy are sold as ready-to-eat products. Soy is available as meat substitutes, miso, soy cheese, soy mayonnaise, soymilk, soy sauce, soy yogurt, tamari, tempeh, textured soy protein (TSP) or textured vegetable protein (TVP) and tofu.

The grading established by the Federal Grain Inspection Service (FGIS) for the USA are the typical standards. Soybeans are divided into two classes based on color: yellow soybeans and mixed soybeans. Each class is divided into four numerical grades (US No. 1, 2, 3, and 4). Six factors are considered in assessing grade designation: test weight, heat damage, total damage, foreign material, splits, and soybeans of other colors. Although moisture, protein, and oil contents are not part of the official grading standards and do not affect the numerical grade, they may be specified on contracts in some markets.

• Keep fans covered. Once soybeans are cooled, cover fan and duct openings to prevent snow or moisture from blowing into the bins during winter storage. Keep fans covered during the spring and summer to limit air from warming the soybeans. Ventilate the top of the bin to reduce solar heating affecting the beans at the top of the bin.

• Monitor stored grain regularly. Outside temperature changes can result in temperature and moisture changes inside the bin. Monitor soybeans at least once every two weeks during winter storage and weekly during the fall until the grain has been cooled to winter storage temperatures. Monitor the soybeans weekly during the spring and summer.

• Use available tools, but don't turn everything over to automation. Improved technology can help better manage stored grain, but you still need to manage the grain and inspect it visually.

• Equalize soybean moisture content. Operating an aeration fan will help move moisture from wet to drier beans. Moisture movement will be minimal without aeration airflow. Initially, fans will have to run longer to equalize the moisture content than to cool the grain. The moisture will not be all the same, but it should become more uniform.

Category: Bacterial

• Bacterial blight Pseudomonas syringae. Symptom: Water-soaked spots on leaves which enlarge and become necrotic; spots may be surrounded by a zone of yellow discoloration; lesions coalesce and give the plant a burned appearance; leaves that die remain attached to plant; circular, sunken, red-brown lesion may be present on pods; pod lesions may ooze during humid conditions.

• Bacterial pustule Xanthomonas campestris. Symptom: Tiny pale green spots with raised centers on both upper and lower leaf surfaces which develop raised pustules in lesion center; pustules usually form in lesions on lower leaf surface; mottled brown areas may develop on leaves if lesions coalesce; small red-brown spots may develop on pods of some varieties.

Category : Fungal

• Rhizoctonia stem rot Rhizoctonia solani. Symptom: Damping-off (pre-or post-emergence death) of seedlings caused by red-brown lesions which girdle the stem; lesions or cankers may be present on the stem of older plants and cause the death of the plant mid-season.

• Rust Phakopsora pachyrhizi. Symptom: Gray or red-brown water-soaked spots on leaves which turn are tan to dark reddish-brown in color lesions may also be present on stems, petioles, and pods; volcano-shaped uredinia (spore-producing structures) are present within the lesions; plants drop leaves and mature prematurely.

Category: Insects

• Armyworms (Beet armyworm, Western striped armyworm). Symptoms: Singular, or closely grouped circular to irregularly shaped holes in foliage; heavy feeding by young larvae leads to skeletonized leaves; shallow, dry wounds on fruit; egg clusters of 50-150 eggs may be present on the leaves; egg clusters are covered in a whitish scale which gives the cluster a cottony or fuzzy appearance; young larvae are pale green to yellow in color while older larvae are generally darker green with a dark and light line running along the side of their body and a pink or yellow underside.

• Cucumber beetles (Western striped cucumber beetle, Western spotted cucumber beetle). Symptoms: Stunted seedling; damaged leaves, stems and/or petioles; reduced plant stand; plants may exhibit symptoms of bacterial wilt; scars on fruit caused by beetle feeding damage; adult beetles are brightly colored with either a green-yellow background and black spots or alternating black and yellow stripe.