Soybean posses a very high nutritional value. It contains about 20 per cent oil and 40 per cent high quality protein (as against 7.0 per cent in rice, 12 per cent in wheat, 10 per cent in maize and 20-25 per cent in other pulses). Soybean protein is rich in valuable amino acid lycine (5%) in which most of the cereals are deficient. In addition, it contains a good amount of minerals, salts and vitamins (thiamine and riboflavin) and its sprouting grains contain a considerable amount of Vitamin C, Vitamin A is present in the form of precursor carotene, which is converted into vitamin A in the intestine. A large number of Indian and western dishes such as bread, `chapati’, milk, sweets, pastries etc., can be prepared with soybean. Wheat flour fortified with soybean flour makes good quality and more nutritious `chapati’. Soybean oil is used for manufacturing vanaspati ghee and several other industrial products. Soybean is used for making high protein food for children. It is widely used in the industrial production of different antibiotics. Soybean builds up the soil fertility by fixing large amounts of atmospheric nitrogen through the root nodules, and also through leaf fall on the ground at maturity. It can be used as fodder; forage can be made into hay, silage etc. Its forage and cake are excellent nutritive foods for livestock and poultry. Soybean being the richest, cheapest and easiest source of best quality proteins and fats and having a vast multiplicity of uses as food and industrial products is sometimes called a wonder crop.

Soybean is one of the important crops of the world. Production of soybean in India at the present time is restricted mainly to Madhya Pradesh, Uttar Pradesh Maharashtra and Gujarat. It is also grown on a small acreage in Himachal Pradesh, Punjab and Delhi.

Season

Soybean grows well in warm and moist climate. The climatic requirements for soybean are almost the same as for maize. A temperature of 26.5 to 30°C appears to be the optimum for most of the varieties. Soil temperatures of 15.5°C or above favour rapid germination and vigorous seedling growth. The minimum temperature for effective growth is about 10°C. A lower temperature tends to delay the flowering. Day length is the key factor in most of the soybean varieties as they are short day plant and are sensitive to photo-periods. Most of the varieties will flower and mature quickly if grown under condition where the day length is less than 14 hours provided that temperatures are also favourable. The time of planting is a very important consideration in soybean. In northern India soybean can be planted from third week of June to first fortnight of July.
Latest research results from the Department of Agricultural Research and Education, ICAR, Government of India, have shown that planting soybean in the last week of June results in maximum yield and after 7 July causes reduction in seed yield @ 40 kg/ha/day.

Well drained and fertile loam soils with a pH between 6.0 and 7.5 are most suitable for the cultivation of soybean. Sodic and saline soils inhibit germination of seeds. In acidic soils, liming has to be done to raise the pH to about seven. Water logging is injurious to the crop.

Mixed cropping of soybean with maize, mandua and sesamum has been found feasible and more remunerative. In mixed stand of maize and soybean, the yield of maize is not affected at the same time 10-12 quintals of soybean per hectare can be obtained. In mixed cropping of maize and soybean, plant maize at 100 cm row spacing keeping plant to plant distance 10 cm and three rows of soybean in between maize rows. Soybean has tremendous scope as an intercrop in arhar, cotton, and upland rice in northern India. In southern part of the country, soybean has a good scope as intercrop in sorghum, cotton, sugarcane, arhar and groundnut. In central India, soybean has been found very remunerative on the fallow lands in Kharif. In low rainfall areas of Madhya Pradesh it has been a common practice to keep the land fallow in Kharif to conserve moisture for a rainfed Rabi crop. It has been found that rainfed Rabi crops after Kharif fallow are generally low return crops. However, when soybean is grown in Kharif instead of keeping the land fallow, about 8-10 quintals of soybean per hectare can be obtained. This is more remunerative than the rainfed Rabi crops on Kharif fallow. And if the Kharif rains were substantial, a profitable Rabi crop could also be raised after Kharif soybean to yield a bonus. Some of the common rotations followed in north India are as given below:

1. Soybean – wheat
2. Soybean – potato
3. Soybean – gram
4. Soybean – tobacco
5. Soybean – potato – wheat

In general the preparation of the land for soybean should be the same as it is for maize. It requires a good seedbed with a reasonable fine texture and not too many clods. Land should be well leveled and be free from crop stubble. One deep ploughing with mould board plough followed by two harrowing or two ploughing with local plough are sufficient. There should be optimum moisture in the field at the time of sowing.

The sowing should be done in lines 45 to 60 cm apart with the help of seed drill or behind the plough. Plant to plant distance should be 4-5 cm. The depth of sowing should not be more than 3-4 cm under optimum moisture conditions. If seed is placed deeper or there is crust formation just after sowing, the seed germination may be delayed and may result in a poor crop stand. Seed rate of soybean depends upon germination percentage, seed size and sowing time. If seed is of 80 per cent germination, 70-80 kg seed per hectare is required. For late planting and for spring crop, seed rate should be 100-120 kg per hectare.

For obtaining good yields of soybean apply 15-20 tonnes of farm yard manure or compost per hectare. A good crop of soybean yielding about 30 quintals per hectare will remove about 300 kg nitrogen per hectare from the soil. But soybean being a legume crop has the ability to supply their own nitrogen needs provided they have been inoculated and there it efficient nodulation in the plant. An application of 20-30 kg nitrogen per hectare as a starter dose will be sufficient to meet the nitrogen requirement of the crop in the initial stage in low fertility soils having poor organic matter. Soybean requires relatively large amounts of phosphorus than other crops. Phosphorus is taken up by soybean plant throughout the growing season. The period of great demand starts just before the pods begin to form and continues until about ten days before the seeds are fully developed. The soil should be tested for the availability status of phosphorus to meet the requirement of the crop. With the application of phosphorus the number and density of nodules are stimulated and the bacteria becomes more mobile. Soybean also requires a relatively large amount of potassium than other crops. A crop of soybean yielding 30 quintals per hectare will remove about 100 kg potassium from the soil. The rate of potassium uptake climbs to a peak during the period of rapid vegetative growth then slows down about the time the bean begins to form. Soil test is the best guide for the application of potash in the soil. In the absence of soil test, 50-60 kg K₂O per hectare should be applied. The fertilizers should preferably be placed, at sowing time, about 5-7 cm away from the seed at a depth of 5-7 cm from seed level.

The soybean crop generally does not require any irrigation during Kharif season. However, if there were a long spell of drought at the time of pod filling, one irrigation would be desirable. During excessive rains proper drainage is also equally important. Spring crop would require about five to six irrigation.

When soybean plants mature they start dropping their leaves. The maturity period ranges from 50 to 140 days depending on the varieties. When the plants reach maturity, the leaves turn yellow and drop and soybean pods dry out quickly. There is a rapid loss of moisture from the seed. At harvest, the moisture content of the seeds should be 15 per cent. Harvesting can be done by hand, breaking the stalks on the ground level or with sickle. Threshing can be done either with the mechanical soybean thresher or some conventional methods used in other legumes. Threshing should be done carefully and any kind of severe beating or trampling may damage the seed coat and thus reduce the seed quality and viability. Wheat thresher can also thresh soybean after a little modification. This would involve change of sieve, reduction of the cylinder speed and increase in fan speed. A moisture content of 13 to 14 per cent is ideal for threshing with thresher.