Soyabean | Description, Cultivation, Importance & Harvesting |

Soyabean(Glycine max) is a leguminous vegetable of the pea family that grows in tropical, subtropical, and temperate climates. Soybean was domesticated in the 11th century BC around the northeast of China. It is believed that it might have been introduced to Africa in the 19th century by Chinese traders along the east coast of Africa[1].

The plant is classed as an oilseed rather than a pulse by the UN Food and Agricultural Organization (FAO). Soy varies in growth and habit. The height of the plant varies from less than 0.2 to 2.0 m. The pods, stems, and leaves are covered with fine brown or gray hairs. The leaves fall before the seeds are mature. The crop can be successfully grown in many states in Nigeria using low agricultural input. Soybean cultivation in Nigeria has expanded as a result of its nutritive and economic importance and diverse domestic usage.

Importance

The most nutritious and most easily digested food of the bean family, the soybean is one of the richest and cheapest sources of protein. Government sources estimate that about 25 percent of Nigeria’s domestic production is consumed directly in rural areas as human food[2]. It is a staple in the diet of people and animals in numerous parts of the world today. Many leguminous crops provide some protein, but soybean is the only available crop that provide high quality source of protein comparable to meat, poultry and eggs.

Soybeans vary in protein from 24-45%. Soybeans vary in oil from 17-35%. Thus the different cultivated varieties can taste quite different from one another.[3]

Soybean oil; an extract from the seed is a major source of healthy oil in the world. It is also processed into soy ice cream, soy yogurt, soy cheese etc.

A by-product from the oil production (soybean cake) is used as a high-protein animal feed in many countries.

Soybean is among the world’s healthiest foods and has numerous health benefits such as;

• It contains vitamins and minerals like vitamin B and is also a good protein, iron and calcium source.

• It helps in cancer prevention due to the presence of isoflavone which can increase the activity of p53, a tumor suppressor which can send signals to the cell death (apoptosis) in cancer cells stopping the growth of cancer and its activities and the formation of tumor too.

• Helps in the reduction of hot flash symptoms as experienced mainly by women in their menopause and peri-menopause stage.

• Aids in the prevention of type 2 diabetes and other chronic health issues by reducing the resistance of insulin in the body and at the same time increasing the synthesis of the insulin receptors.

• It helps in suppressing appetite thereby eliminating the possible chances of feeling hungry or overeating which in turns helps in weight loss and healthy weight gain too because of the presence of fiber and protein content.
• It is also good for the heart, digestive systems, bones, controlling of the thyroid hormone especially when it comes to goiter and numerous others.

Cultivation

In Nigeria, soybean cultivation starts in May/June. Soybeans grow well on almost all types of soil, with the exception of deep sands with poor water retention. The optimal soil pH is 6.0 to 6.5, therefore liming may be required. With respect to climate, the soybean grows best in temperate zones. The soybean is a so-called short-day plant, meaning that flowering occurs when the nights begin to lengthen. The breeding of varieties with different maturation periods (maturity groups) has permitted optimal production in a wide range of latitudes. Rainfall in the range of 500 to 700 mm. is required for good yields. Adequate water supply is especially important during the period of pod and seed development (pod filling stage). Irrigation is now considered an essential factor for increased profit and security to the farmer.

Economic potential

As human population increases, so does our need for protein. As we grow from babies to adults, we have a great primary requirement for protein.

Worldwide consumption of soybean is nearly 11 million tons. Africa consumes about 618,000 tons annually, and uses another 4,800 tons for animal feed. Nigeria is the largest consumer of soybeans in sub-Sahara Africa followed by Uganda.

 (Ajay et al. 2011)[6] concludes that soybean is an excellent source of high quality protein with a low content in saturated fat, with no cholesterol, and a great amount of dietary fiber. Therefore, the possible use of soybean in functional food design is very promising, since the consumption of soybean protein and dietary fibre seems to reduce the risk of cardiovascular diseases

Nigeria currently produces soybean worth $85 million in the international market and though most of the nation’s soybean is consumed locally where they are used in the production of soymilk and specially formulated foods to help malnourished infants and children, the international market for the product is growing and sustainable[7].

GENERAL INFORMATION

Production

World production of soybeans has increased by a factor of eight in the last half century to reach its present level of over 100 million metric tons per year. The leading producers are the U.S.A. (45%), Brazil (20%) and China (12%). Much of this phenomenal growth was due to the sharp increase in the U.S.A. production between 1950 and 1970, and to the introduction of the soybean to Brazilian agriculture in the sixties[8].

Twenty-one African countries now produce soybean. Nigeria has the highest 6-year (2000-05) average production of 486,000 tons on an area of 553,260 hectares, followed by South Africa with 205,270 tons from 122,870 hectares, and Uganda with 155,500 tons from 139,500 hectares[9]. Nigeria presently produces about 500,000 Metric tonnes of soybean annually making it the largest producer of the product on the African continent.[10]

Improved Varieties

IITA in collaboration with National Cereal Research Institute (NCRI) developed a new variety tagged TGX 1835-10E and was released to farmers in 2009. This variety aside from being resistant to the Asian rust, the variety is also high-yielding, averaging 1655 kg/ha grain and 2210 kg/ha fodder in field trials in Nigeria. It is also early-maturing, has good promiscuous nodulation character, and resists pod shattering and other prevalent diseases when compared to the local variety[11]. Subsequent development by these agencies resulted in the introduction of three new varieties in Nigeria and Malawi (2011). These varieties (TGx1740-2E, TGx1987-10F, and TGx1987-62F) outperformed the standard and local checks grown in the two countries, offering high grain yield in multiple locations under on-station and on-farm trials. In Nigeria, medium-maturing varieties TGx1987-10F and TGx1987-62F proved highly resistant to Rust, Bacterial Blight, and Cercospora Leaf spot. The varieties are preferred by many farmers because they smother weeds and reduce the cost of weeding[12].

Planting

Clear all vegetation before land preparation. The seedbed may be prepared manually with a hoe or an animal-drawn implement or tractor. Well-prepared land ensures good germination and reduces weed infestation. You can plant on ridges or on a flat seedbed.

Choosing your seeds

Experts warn that soya bean variety selection should be based on maturity, yield potential, lodging, drought tolerance and resistance to pests and diseases. The maturity period should be the first consideration when choosing a variety suited to your geographical zone. Use seeds that are not more than 12 months old to ensure good germination. Sort out the good seeds for planting to ensure that they are free from insects, disease infestation and weed seeds. Do not purchase seeds from the open market as the germination potential is not guaranteed. Planting poor quality seeds will not produce a good yield.

Conducting Germination Test

It is highly recommended that seed test be done before planting and  the germination rate should be 85 per cent or more to obtain a good stand.

Inother to conduct a quick seed germination test, select 400 seeds randomly and sow 100 seeds each in four wooden or plastic boxes or a prepared seedbed. Sow one seed per hole at a distance of 10cm between the seeds. Soak cloth or paper-lined germination boxes or the seedbed well with water before sowing and provide water every morning and evening. Start counting the seedlings five days after sowing and complete the counting within 10 days. A total count of 320 germinated seeds or more indicates a germination rate of 80 per cent and above. When the percentage of germination is 80 per cent or less, the seed rate has to be increased accordingly to achieve 100 per cent.

Fertilizer Application

IITA advises that a good fertiliser recommendation for soya bean production depends on a good soil test. Under normal conditions, soya bean as a legume should provide itself with nitrogen through biological nitrogen fixation. Until nodulation occurs, the soya bean plant depends on soil nitrogen for growth. Phosphorus is often the most deficient nutrient, therefore, apply optimum phosphorous fertiliser for good yield. The institute further advises farmers to incorporate the fertiliser into the soil during harrowing and levelling of the field.

Pests, diseases and weeds

Perennial and most annual weeds are a problem to soya bean in its early growth stages. A properly timed weed control programme can minimise the effects of weeds. Weed control in soya bean could be manual or chemical, or both.

Manual weed control: Carry out the first weeding at two weeks after planting and the second at five to six weeks after planting. Avoid weeding immediately after a rainfall as this will lead to transplanting the weeds. Poor hoe weeding or delay in weeding can cause significant reduction in yield.

Chemical weed control: Herbicides, if used properly, are safe and effective in controlling weeds in soya bean cultivation.

The choice of herbicide, however, depends on the predominant weed species and the availability of the herbicide. Herbicides are available for pre-emergence or post-emergence weed control in soya bean. If herbicide is applied at planting, one weeding may be required at five to six weeks after planting.

Several different insects infest soya bean fields, but few are normally of any economic importance, and the species that cause damage are usually not abundant enough to warrant control measures. In the vegetative stage, the crop is very tolerant of caterpillars but very susceptible to silverleaf whitefly attack.

Harvesting

This normally commences in late October and runs through November every year. The crop is harvested 3 – 4 months after planting, depending on the time of sowing and seed variety. Early-maturing types can be harvested for grain 70 days after planting and late-maturing needs up to 180 days. Soybeans can be harvested by hand or by combined harvesters (this only at full maturity or after windrowing – cutting plants and leaving them in rows for wind and sun to dry properly).

Soybean is mature for harvest when most leaves have aged and turned yellow at least one pod per plant has turned brown or black. The pods are still green yet filled with seeds for vegetable soybeans. Take the following steps when harvesting soybeans:

• The plants are cut near the ground or pulled with their roots once threshed
• Dry the soybeans to below 12 % moisture content before storing.
• Keep in a clean store and prevent weevil attack by any of the means described under storage pests.

Most small scale farmers achieve yields of about 500-1000 kg/ha; though 3000 kg/ha is possible with good husbandry practices and recommended varieties[5].

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References

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