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Posted 01/21/2021 in Agricuture by Wallace Mukoka

HOW MUCH DO YOU KNOW ABOUT SOYA BEANS?


HOW MUCH DO YOU KNOW ABOUT SOYA BEANS?

Soya Bean Production

Soils and climate

The soyabean is suited to soils with high clay content. The optimum pH is 5.5. Soyabean requires reliable rainfall particularly from flowering to pod maturity. It is a good crop to grow in rotation with maize, cotton and wheat.

Fertilizer Management

Soyabeans grow well on residual fertiliser. General recommendation is 200 - 300 kg/ha of either a Compound fertiliser (D or L), Gypsum or Single Super Phosphate before planting. Soyabeans respond well to manure application. Soyabeans do not need much nitrogen either in the basal fertilizer or as top dressing they are able to obtain their nitrogen requirements from the soil air. It is therefore essential to apply Bradyrhizobium inoculant to the seed at planting. Do not leave the inoculant in a hot place, but store it in a cool, dark place. When ready to plant, the inoculum is mixed with a little water and sugar, and applied to the seed immediately prior to planting. One packet of inoculant is required for each 100 k…

Cultivars

There are two basic types of soyabean cultivars:

Determinate and indeterminate.

Determinate cultivars grow vegetative for about six weeks and then begin flowering, having put on 10 to 12 leaves. Once flowering begins, no further new leaves are produced on the main stem. Indeterminate cultivars, on the other hand, grow vegetatively for about six weeks, then begin flowering when the main stem has about 10 leaves, but at the same time as flowering, the stem continues to grow for another three weeks or so, producing another five to seven leaves. Determinate cultivars are better suited to warm fast growing environments where irrigation is available, like the lowveld, whilst on the midlevel and highveld, both types are suitable. Under drought conditions, indeterminate varieties may have some advantage over determinates. Some of the cultivars available include Soprano and Solitaire, which are indeterminate, and Storm and Soma, which are determinate

Planting and crop management

The seed rate is about 100 kg per ha. The desirable plant population is around 350 000 plants per ha. The minimum plant population is 200 000 plants per ha, while the maximum is 500 000 plants/ha. The row spacing may be from 25 - 90 cm. Do not plant seed deeper than 5 cm. Covered the seed such that the soil forms a slight mound over the row, as this makes it easier for the seedling to emerge. Seed should be planted 25-50 mm deep, depending on soil texture.

If soil crusting occurs before emergence, wetting the soil with irrigation or breaking the crust with a ‘millipede implement’ will improve emergence. Planting is ideal around mid-December. A fungicide seed dressing of Thiram 80 WP (85 g/50 kg seed) or Captan 50 WP (125 g/50 kg seed) will help ensure good emergence. Soyabeans are particularly sensitive to weed competition during the first six weeks of the season. Soyabeans are very susceptible to drought during the pod-filling stage.

Pests

Semi-looper caterpillars

Often a problem during the flowering and seed-fill period. They eat the leaves and sometimes the pods. Normally controlled by a naturally occurring virus disease, which kills the caterpillars. Caterpillars that have died from the disease are black and hang from the leaves. These may be collected, crushed, mixed with water and sprayed around the field to help control other caterpillars. If the virus is not killing the semi-loopers then an insecticide spray may be required.

Diseases

Frog Eye Leaf Spot (Cercospora sojina) 

Most cultivars available today are resistant to this disease.

Rust (Phakopsora pachyrhizi).

The Rust disease may be recognized as numerous small grey to russet coloured tufts on the underside of leaves. They may appear similar to red spider mites. In advanced stages the leaves become distinctly yellowy-brown and a light brown cloud of spores are seen in and above the canopy when the plants are shaken. It can be controlled using a fungicide spray. A number of chemicals are available, such as Punch Xtra (350 to 500 mL/ha) and Shavit® (500 ml/ha). Two or even three, fungicide sprays are at 3 week intervals beginning at first flower. Ensure good leaf cover when spraying.

Red Leaf Blotch (Pyrenochaeta glycines).

Severe infections can reduce seed yields by 30% - 50%. D. Solitaire and Soprano are moderately resistant. Chemical control is not available.

Harvesting

a) Hand harvesting.

Suitable for small areas.

Advantages of hand harvesting are that:

Losses can be reduced to a minimum

Soyabeans of a high quality are produced

The beans normally have a high viability.

Therefore, hand harvesting is suitable for seed production.

 b) Mowing or cutting by hand and shelling.

A variation is to use a mower to cut the plant material, and a mechanical 

winnower for the final cleaning. This method should enable an output of ± 150 kg (3 bags)/labour/day. This method enables harvesting to commence before the pods split, but allows sufficient moisture to be lost, thereby preventing mould developing in the established cocks or stacks.

Swather plus combine.

This method involves the use of a swather to cut and wind-row the crop before it is combined. A pick-up attachment is required to be fitted to the combine table.

d) Combine harvesting.

Large areas are usually reaped by combine harvester and losses are inevitable. The degree of loss depends on the efficiency of the machine and operator, evenness of the land, the height of the pods off the ground, lodging, the moisture content of the beans, and weed control.


Author; Wallace Mukoka


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