By: Dr Samuel Nsubuga (Smart Agribusiness Forum Africa)
Soybean is known as the golden bean and Soybeans belong to the legume crop family and are basically native to East Asia. Its botanical name is Glycine max. Soybean is an exceptionally nutritive and very rich protein food. Soybean oil is one of the most popular edible oil used in Africa.
Soya also used as milk product and available in the form of soya chunks.
HEALTH BENEFITS OF SOYBEAN
Some of the Soybean health benefits are mentioned below.
• Soybean is low in fat with no cholesterol.
• Soybean contains essential heart friendly omega-3 fats.
• Soybean provides important minerals such as calcium, magnesium, iron and selenium.
• Soya is rich in probiotics in the form of fermented soy products, such as tem soy yogurt.
• Soybean is an excellent source of fiber.
• Soybean is a good source of enriched Calcium and Vitamin B12.
• Soybean is a complete protein food, containing all the amino acids essential to human body.
• Soybean contains isoflavones which are good in reducing risk of various cancers, heart disease and osteoporosis.
AGRO-CLIMATIC CONDITIONS FOR SOYBEAN FARMING
Soybean thrives well in warm and moist climate. A temperature of 26 to 32°C appears to be the ideal for most of the varieties of soybean. Soil temperatures of 16°C or above support rapid germination and vigorous seedling growth in soybean farming.
A lower temperature may cause to delay the flowering. Day length is the key factor in the soybean varieties as they are short day plants.
BEST SEASON TO GROW SOYBEAN
Best season to plant soybean from 3rd week of June to mid of July/August.
SOIL REQUIREMENT IN SOYBEAN FARMING
Soybean requires well drained and fertile loamy soils with a pH range between 6.0 and 7.5 are most favorable for its cultivation.
Saline soils and sodic inhibit germination of Soybean seeds. Water logging damages the crop, so it is mandatory to have good soil drainage in rainy season.
SEED RATE IN SOYBEAN FARMING
The seed rate varies from 16-25kg/acre. Seed rate also depends on seed size, germination percentage.
CROP ROTATION IN SOYBEAN FARMING
In Soybean farming, mixed cropping crops like sesame & maize has been found feasible and fetching more returns. In inter cultivation, plant row spacing of maize should be at 100 cm keeping plant to plant distance 10 cm and 3 rows of soybean in between maize rows. Soybean has excellent scope as an intercrop in cotton, and upland rice too.
LAND SELECTION AND ITS PREPARATION IN SOYBEAN FARMING
Land selection is very important in soybean farming as this will impact the overall production of soybean. The main land must not have been sown with soybean crop in the previous season to avoid volunteer plants that cause admixture.
Land continuously cultivated with soybean may harbor wilt pathogen. so these kind of fields must be avoided. By following the crop rotation, endemic pathogen can be reduced. A soil with high organic matter defiantly helps in leading production of vigorous seed.
The field should be made into ridges & furrows of 1feet wide or beds & channels of 4 feet x 6feet depending on cultivation practices followed.
Different pre-planting factors should be taken into account because they influence eventual soybean establishment, quality and quantity of seed/grain. Growers must make a plan on when and where to purchase inputs, timing of applications and scouting for pests and diseases. They can engage in the following pre-planting activities:
Before seedbed preparation it is advisable to clear all forms of vegetation from the field. Land may be prepared by hand hoe or animal-drawn ploughs or tractor. Single ploughing and harrowing is recommended for preparing a suitable soybean garden.
An ideal soybean seedbed should comprise fertile loam soils that are loose and well aerated to ensure rapid germination and seedling emergence which reduces weed pressure. A fine seed bed also provides adequate moisture and optimum temperature (above 21oC).
Farmers must avoid tight, high clay soils since these soils are generally low in humus, are imbalanced in nutrients and act as barriers to seedling emergence.
SEED SELECTION IN SOYBEAN FARMING
Soybean seeds used for sowing must be from an authentic source. Genetic purity is an important factor in selecting sowing seeds. Avoid diseased, immature, hard, damaged, shrunken seeds. Seeds selected for sowing should also be vigorous for a good field stand.
Successful and efficient soybean production requires farmers to select varieties with maturities that make the best use of the growing season in their areas. One can select for good yields and important characteristics such as oil and protein content.
Depending on the fields’ pest and disease histories, its recommended to choose varieties with genetic resistance to those pests and diseases. Where the farmer has several soybean fields, multiple soybean varieties may be planted to ensure genetic diversification across fields.
Like many oil crops, soybean seed rapidly loses viability under ambient conditions. This results in poor plant stand, leading to considerable reduced productivity. It is therefore recommended to always use seed from credible sources and or seed harvested in the previous season to avoid poor germination.
Before planting, growers have only one chance to establish the potential optimum stand by carrying out a germination test. Knowing the potential germination rate helps farmers to know what proportion of seeds to be planted are viable.
The germination experiment is simple and can be done by farmers as follows:
• Count out 100 whole soybean seeds and place them on one half of paper towel.
• Wet the paper towel and allow free water to drip off for a minute.
• Lay the wet towel on a clean surface and fold the towel over and roll it into a moderately tight tube.
• Position the rolled towel so the tube is upright so that roots will grow downwards while shoots will grow up-wards, for ease in removing seedlings during counting.
• Keep the rolled towel in a warm place (between 23° and 30°C). Count the first germinated seeds after three days by opening the towel. Fold and roll back into a tube.
• Repeat counting after another three to four days. Good viable seeds are expected to have a germination rate of over 90 percent, notably because germination time for most legumes is between 5 – 7 days.
SEED TREATMENT IN SOYBEAN FARMING
To control any seed borne diseases, Soybean seeds should be treated with carbendazim fungicide at 4g kg-l of seed.
SOWING IN SOYBEAN FARMING
The sowing in Soybean farming should be done in lines 45 cm – 60 cm apart with the help of seed driller or behind the plough or manual. Plant to plant distance can be kept from 4 cm to 5 cm. The sowing depth of soybean seed should not be more than 3 cm – 4 cm under ideal moisture conditions.
Actual planting is a critical period for managing soybeans because it’s during this stage that growers have to suc¬cessfully implement or apply all the decisions made during the pre-planting stage. This section will provide agro¬nomic recommendations and tips to consider during the planting stage. In fields where inoculated soybean has never been grown, seed should be inoculated with Rhizobium japonicum which can be purchased at Makerere University, School of Agricultural Sciences.
INOCULATION OF SOYBEAN
During planting it’s recommended that the farmer dresses/ mixes the soybean seed with an inoculum Rhizobium Japonicum. This is a nitrogen fixing bacteria that improves on nodulation capacity and subsequently yield of soybean.
Inoculation is most important in the field where soybean has never been grown.
1. Take clean water in soda bottle, add one table spoonful of sugar and shake well to dissolve. You have made an inoculum sticker.
2. Take a debe (15kg) of clean soybean seeds or any big sized seeds
3. Empty the seeds into clean basin.
4. Pour the prepared inoculum sticker into the seeds
5. Empty the MAK BIO-N-FIXER inoculant onto the wetted seeds.
6. Mix the seeds thoroughly so that each seed is uniformly coated with the inoculant.
7. Cover the inoculated seeds with paper, cloth or basket to protect from direct sunlight. Sow the seeds immediately in moist well prepared field.
MANURES AND FERTILIZERS IN SOYBEAN FARMING
5ton of well decomposed compost (Cow dung or any Farm Yard Manure (FMY) is spread along with basal application of 150-200 kg super phosphate ,40 kg urea and 50 kg muriate of potash per acre in splits.
Phosphate at 2weeks,one month, and at 2months
Urea at 2months
Muriate of potash at 3months, and then after 3weeks after first application. This should be in accordance with soil testing!
WEED CONTROL IN SOYBEAN FARMING
Soybeans are particularly sensitive to weed competition during the first weeks of the season. Weeds are a major threat to production of most crops, because they deprive plants of essential growth resources like water, nutrients and light.
Besides, seeds from certain weed species not only interfere with harvest operations but also reduce quality and price of grains. In soybean, annual and perennial weeds are problematic at early vegetative stage.
Weed control is very important because it reduces competition for nutrients, water, and light and prevents mixing of weed and soybean seed during harvesting.
Later after the crop has fully established, hand weeding can be conducted twice in a cropping season at 2 and 5 weeks after planting, respectively. Unfortunately, hand weeding though cost-effective can facilitate the spread and propagation of perennial weeds with underground tubers and rhizomes.
Herbicide control when cautiously applied can effectively control weeds in soybean. Choice of herbicide is influenced by weed species characteristics i.e. life cycle, nutrient requirements and modes of reproduction.
Applying roundup (glyphosate) to soybean fields before planting is highly recommended. It significantly reduces the time before emergency of weed seed after planting, leading to reduction in the number of weeding and subsequently total cost associated with hand weeding.
Deployment of integrated approaches for weed management are particularly important to prevent weeds from producing seed throughout the cropping cycle.
This can be achieved by farmers ensuring that soybean seeds they intend to sow are not contaminated with weed seeds and have over 85% germination percentage, since vigorous seedlings are capable of suppressing weeds.
IRRIGATION IN SOYBEAN FARMING
The soybean crop generally does not require any irrigation during rain-fed season. But, if there were any a long drought at the time of pod filling, one irrigation would be required. During rainy season, make sure crop soil has proper drainage to avoid the water logging. Rainy crop would require about 6 to 7 irrigation.
PEST AND DISEASE CONTROL IN SOYBEAN FARMING
The major pest in soybean farming is heliothids which makes holes in young pods and eats the seeds. Collect the worms and destroy them or spray with Dimethoate Methyl dematon (pesticides with this as an active ingredient) or black off or nimbecidine or ALPHA
During the growing stages of the soy seed crop, incidence of wilt being observed. The affected plants with wilt will turn brown and die, these plants can be removed when they get noticed.
The affected area of crop is sprayed using fungicide solution. Another common disease in Soybean farming is “Powdery mildew” it causes white powder deposits on the leaves. This disease can be controlled by spraying Dithane M45 at the rate of 4grams / liter of water or mister 72 or any other curative fungicide.
HARVESTING OF SOYBEAN
The maturity of soybean crop period ranges from 50 to 145 days depending on the varieties used for cultivation. It should be an indication of maturity when the leaves turn yellow and drop and soybean pods dry out very quickly. There would be a rapid loss of moisture from the seed. At harvesting time, the moisture content in the seeds should be about 15 %. Harvesting should be done by breaking the stalks on the ground level or hand, or with sickle.
Harvesting is the last important operation to be considered for the production of good quality seed and grain. Most soybean varieties are harvested within a period of 90 – 120 days after planting. Timely harvesting of seed minimizes seed deterioration in the field, infestation by insects and losses from physical damage.
Delayed harvesting may cause the pods to start shattering in susceptible varieties leading to yield loss.
Soybeans should be harvested as soon as the plants have dried.
The crop is ready for harvesting when pods dry and give a rattling sound when shaken. If the harvesting is delayed, the pods may shatter with a consequential loss of seed.
a) Hand harvesting; this method is suitable for small areas, where a large labour force is readily available.
The advantage of this method is that losses are kept at a minimum, soybeans of a high quality are produced and the beans are normally of a high viability. Therefore the hand harvesting is suitable for seed production.
The usual system of hand harvesting is to allow laborers to cut or pull as much plant material as they are able to thresh in a day.
Can be done manually or mechanically. At threshing, the seed should have a moisture content of 14-15%. It is important that seed of different varieties are threshed on different days to avoid admixing of the varieties. The seed should be dried on clean tarpaulins to avoid soiling and contamination.
Drying of seed should not be done at high temperatures because this adversely affects the quality. Proper drying of seed reduces storage losses.
Can be natural or artificial. Natural drying is done by the normal movement of ambient air around the moist seed spread on trays, canvas or directly on paved floors.
Artificial drying is done with heated air blown mechanically through the seed; the temperature of this air should not be above 35 to 37oC.
Total drying time is determined by the initial and final moisture content of the seed, the depth of the seed, the air velocity and temperature, and the relative humidity of the atmosphere.
During this exercise, seed should be graded according to variety and quality. Also remove all impurities, including inert matter and weed seeds.
After the seed has been cleaned, it should be weighed and packed. Seed should be dry before storage so that its viability can be maintained during the storage period.
Soybean should be stored at a moisture content of 10 – 12% or less. Seed is sufficiently dry when it cannot be dented with the teeth or fingernails.
Dry to 12% moisture for storage of 6–12 months and to 10–11% for longer storage. If seed is stored with high moisture, it will accumulate heat and rapidly deteriorate.
YIELD OF SOYBEAN
Crop yield depends on the variety of seed cultivated and agronomic practices .An average yield 7 to 25 tons/acre can be expected.