Globally legumes play vital role in human nutrition since they are rich source of protein, calories, certain minerals and vitamins. Among which soybean is probably the largest source of vegetable seed oil (20%) and protein (40%). Owing the nutritional and health benefits of soybean, it excited the growers in recent years. US, Argentina, Brazil and China claims as the biggest producers of this super crop, the modern technologies and changes in their agronomic practices is worth to discuss on its possibility in Indian scenario.
Area of Cultivation
Production of soybean in India (4% of global) 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.
Soybean grows well in warm and moist climate. 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 favor rapid germination and vigorous seedling growth. 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 plants. In northern India soybean can be planted from third week of June to first fortnight of July.
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. Water logging is also injurious to the crop. Studies done at University of Wisconsin also revealed an increase in protein concentration by 20% and 16% decrease in oil concentration as soil pH rouse from 4.5 to 7.0.
Mixed cropping of soybean with maize, mandua and sesamum has been found feasible and more remunerative. 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. A randomized complete block study on row spacing and plant density showed a higher protein content and lower oil content at 19 cm compared to 75 cm row spacing. 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. Some of the common rotations followed in north India are:
Soybean – wheat , Soybean – potato , Soybean – gram , Soybean – tobacco , Soybean – potato – wheat
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. Seed rate of soybean depends upon germination percentage, seed size and sowing time.
Fertilizer and Nutrient Management
For obtaining good yields of soybean apply 15-20 tonnes of farm yard manure or compost per hectare. 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. 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 become more mobile. Soybean also requires a relatively large amount of potassium than other crops. 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.
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.
Dr. Veda Krishnan and Dr. Archana Sachdev
Scientist, Division of Biochemistry
Indian Agricultural Research Institute (IARI)
New Delhi – 12