By Professor Sheunesu Mpepereki

MANY potential soyabean farmers have failed to get started because they could not access inputs.
In this first article on soyabeans, we shall look at the input requirements.
We shall also attempt to give some advice on how farmers can deal with input shortages.
To grow a soyabean crop several key inputs are required.
These include seeds, an average of 100 kilogrammes (kg) will plant one hectare.
Soyabean seed currently costs just under US$40 per 25 kg pocket.
One packet of Rhizobium inoculant is enough for 100 kg of soyabean seed to plant a hectare.
The current price of inoculant is US$5 per packet.
Rhizobium is mixed with seed before planting.
Basal fertilisers can be compound ‘L’ or Cotton Fert which contains boron.
Compound ‘D’ can also be used, but it does not contain boron required for good oil formation in the seeds.
Single super phosphate or manure can also be used to fertilise soyabeans.
Herbicides are important where large areas are planted or where labour is not readily available for weeding.
Pre-emergent herbicides are applied after planting, but before the crop germinates, usually within 24 hours after planting.
Metribuzin for broad leaf weeds, Alachlor or metalochlor for grasses are mixed and applied after planting.
Where weeds have come up before planting, glyphosate (roundup) can be added to the tank mix of metribuzin and Alachlor to kill off the weeds.
Application rates depend on soil clay content.
Farmers need to read the label before applying any chemicals.
Where weeds appear after crops have germinated, post emergence herbicides are used; e.g Classic or Basagran for broad leaf and Agil or Fusilade for grass-type weeds.
Again rates are indicated on the container labels.
Other weed control chemicals are available and farmers should shop around and ask those with expert knowledge.
Fungicides to prevent soyabean rust are applied at first flowering, while insecticides against leaf eaters and semi-loopers are applied only when the number of leaves eaten approaches 30 percent of total leaf area.

Handling and use of the soyabean production inputs

Soyabean seed at 100kg per hectare
Several companies distribute seed.
These include Seed-Co, Pannar and ARDA Seeds.
Because soyabean is a relatively new crop in most smallholder areas, one may fail to find seed in remote rural outlets.
Special orders may need to be placed with inputs suppliers.
However, as more farmers adopt soyabean, it is expected that seed will become more readily available as dealers take advantage of the expanding market.
Soyabean seed may be unavailable in remote areas.
Farmers failing to access certified seed may use retained seed which, with careful grading, can still give satisfactory results for two or three cropping seasons before seed-borne diseases severely reduce yields.

Using seed from own crop
Farmers may carefully select seed from their soyabean crop at harvesting time.
A good stand with healthy plants must be selected and harvested separately.
The main drawback in using retained seed is carryover of seed-borne diseases.
In some cases the seed may have matured under drought conditions such that it is immature and will not germinate.
Seed must be carefully dried upon harvest.
If stored wet, it will become mouldy and fail to germinate.
Farmers are encouraged to use certified seed at all times.
Retained seed should only be used as a last resort and only after checking its ability to germinate.
Seed must be cleaned before use.
Remember dirty seed carries a lot of disease germs that will affect your crop after germination.
To check for seed viability, a germination test must be done.
This involves planting say 100 seeds in moist soil and checking how many have germinated after a week.
A germination rate of 75 percent or higher is acceptable.
Low percent germination can be compensated by increasing seeding rate if necessary.
Removing diseased or immature seeds can improve germination rate.
Farmers are warned never to plant soyabean seed that has been stored for more than one season without first testing germination percent. Even certified seed may lose its viability after storage for more than one season.
If you buy certified seed and fail to plant this season, do not keep it for next season; the chances are it will germinate poorly or not at all!
Sell or exchange it for fresh seed harvested in the immediate past season. Do not pay for uncertified soyabean seed until it has first been checked for germination.
Soyabean that has failed to germinate is still good for human or livestock food or extracting oil; it can still be sold at market prices.
No chemicals are required to protect the soyabean seeds from weevils; the skin of soyabean seed is too tough for most weevils to bore in.
In some cases seed may be treated with a fungicide e.g. Thiram or other seed dressing to promote good germination.
Soyabean seed should be stored in well aerated bags.
Air-tight plastic containers should not be used to store soyabean seed as it will quickly lose its ability to germinate.
Seeds are alive and need air to breathe.
Rhizobium inoculants at 1 x 80g sachet per hectare
Rhizobium inoculant consists of special bacteria packed in sugar cane waste in plastic bags.
The bacteria are harmless to human beings.
They make nitrogen fertiliser for the soyabean plant.
They are mixed with seed before planting.
Rhizobium inoculants can be ordered direct from the Government-owned factory at Soil Productivity Research Laboratory (SPRL), Grasslands Research Station, near Marondera or through the Chemistry and Soils Research Institute of the Department of Research and Specialist Services (DRSS) head office at Harare Research Station or your provincial AGRITEX office.
Some seed suppliers provide the rhizobium inoculant with the seed. Orders can also be placed through input suppliers e.g. agro-dealers that sell soyabean seed.
Farmers should note that soyabean seed sold in Zimbabwe is not pre-treated with rhizobium inoculant.

Some contact details for Rhizobium supplies are as follows.
l Rhizobium Inoculant Factory, Grasslands, Marondera (Ph: 079-24391).
l Chemistry and Soils Research Institute (DRSS) (Ph: 04-704531).
Fungicide application rates (ml per ha) vary with the product, but often range from 500 – 1000 ml/ha).
The manufacturer’s instructions must be followed strictly; the recommended dosage should never be exceeded as this can kill the crop.
Apply at least one spray of fungicide at flowering as a preventive measure.
Do not wait for symptoms to appear. It may be too late.
Important points to note about fertilising soyabeans include the following.

l A higher fertiliser rate is used if soil fertility is low; and a lower rate for soils where the previous crop was heavily fertilised e.g. soyabean after winter wheat.
l Boron-containing compound fertiliser with low N content e.g. ‘L’ is preferred.
l Phosphate can be applied as single super phosphate (SSP) at 20-30kgP2O5/ha to supply P.

Fertiliser Application methods include broadcasting with a Vicon or fertiliser spreader and disking in before planting.
The Vicon is calibrated to deliver the required amount of fertiliser per hectare,
Basal fertiliser can be dribbled by hand into the planting furrows one handful per 10 metre row.
Basal fertiliser can be applied in a band e.g. with planters fitted with a fertilizer hopper that can be calibrated to give the required rate.
Soyabean crops that have received rhizobium inoculant at planting do not need N top dressing fertiliser unless the crop looks yellow and N-deficient.
Ammonium nitrate or urea may be used to top dress soyabean crops planted without inoculant.
A rate of 75 – 100 kg per ha broadcast over the crop at 4 – 5 weeks after emergence, repeated at pod-fill stage will give good yields.
Animal manure can also be applied as basal fertiliser on soyabeans. Manure is a slow release fertiliser which supplies nutrients and improves the soil conditions for crop growth.
In this article we have provided information on main inputs for the reader to get out there and plant a soyabean crop.
We shall be giving more information on soyabean production, processing and marketing and other farming tips in subsequent articles in this publication for the benefit of our farmers.