By Professor Sheunesu Mpepereki

IN this second article on soyabean production, we shall look at how the farmer prepares the land and how the soyabean crop is planted.
Land preparation is a critical stage in the soyabean production cycle.
Poorly prepared land may result in soil erosion, poor germination, weed infestation and harvesting losses.
In preparing the seed bed, land must be ploughed, disked and harrowed if necessary to obtain a fine tilth.
Care must be taken with virgin land or heavy soils, where large clods may then cover seeds reducing emergence.
Disking and rolling may be necessary in such cases.
Tillage practices include what is termed conventional tillage where land is ploughed and disked to produce a fine seedbed.
The land must be flat if a combine harvester is to be used so that it cuts close to the surface.
On virgin or long fallow the land must be stumped and deep ploughed. Alternatively, the land can be ripped.
The field is disked after ripping or ploughing.
A light disc or spike harrow may be used to break clods to produce a smooth seedbed just before planting if necessary.
On previously cropped fields the soil should be disked preferably after soaking rain.
This will ensure incorporation of crop residues and weeds will be turned under.
A fine seedbed for planting will be produced.
If some weeds have come up before planting, either disc lightly and plant or plant and then burn off the green weeds with glyphosate mixed with pre-emergent grass and broad leaf herbicides in one tank mix.
In all cases where you plan to mix herbicides, check first to see if the herbicides are compatible for mixing.
If tillage implements are not readily available and the field is weedy, use a weed killer (paraquat or Roundup herbicide) to kill off the weeds.
Drill in seed or mark rows, plant and cover lightly.
Alternatively, pre-emergent herbicides (against broad leaf and grasses) can also be applied after planting, mixed with the weed killers.
Conservation tillage is also called ‘zero tillage’ or ‘reduced tillage’.
In this system, the soil is not turned (by ploughing).
Instead a furrow is opened just for the seed and fertiliser application.
Herbicides are then applied to control weeds.
We now look at the implements for soyabean production.
The implements listed below cover all the stages of the crop production cycle and are suitable for large scale production.
Small to medium scale production requires the following essential implements for soyabean production: disc harrow, for land preparation, a spike harrow for preparing seed bed and covering if hand planting, a cultivator used as a row marker or for weed control and a Boom or knapsack sprayer for applying chemicals.
Large scale production requires the following: Rhome harrow/disc harrow, Seed drill or planter, Boom sprayer and Spike harrow.
We now turn to planting of soyabean.
Planting must be undertaken when the seed bed has adequate moisture.
Soyabean has high oil content and will fail to germinate if planted with inadequate moisture in hot soils.
The oils in the seed start to ferment.
Please note, farmers should NEVER DRY PLANT SOYABEANS!

Planting depth
Planting depth is critical.
In sandy or light soils seed can be placed up to four centimetres (cm) deep.
In heavy soils (high clay content) a depth of two – three cm is adequate.
If planted too deep, soyabean will fail to emerge.
If it rains soon after planting, a crust may form that will hinder germination.
A light spike harrowing across the rows will aid germination.

Hand Planting
Cut shallow planting furrows into moist soil using a row marker.
Ox-plough furrows can be too deep.
Dribble basal compound fertilier into the furrow at 150 – 250 kg/ha.
In fertile soils e.g. previously well-manured, fields previously planted to well-fertilised cotton or wheat, use less basal fertiliser.
One handful should be dribbled on one metre length to give approximately 150 kg per ha.
Follow-up immediately with inoculant-dressed seed.
Cover to depth of two – three cm immediately.
Seed may be covered by dragging a tree branch over the furrow, using feet or other means.
A spike harrow is quicker.

Note:
Planting furrows must be fertilised, planted and covered as soon as possible.
If left open soil dries out and inoculant may be killed by the high drying temperatures.
If dressed seed is left uncovered, the bacteria are exposed to sunlight and ultra-violet light and are killed.
If any of this happens, the soyabean will not benefit from N fixation by the rhizobia, plants will be yellow and the farmer may have to buy expensive ammonium nitrate to top dress the soyabean crop.

Using a planter
Soyabean can be planted with a planter.
After inoculating, spread seed out in shade to dry out surface moisture.
Adjust the planter to give 30 – 50 cm rows.
The closer the rows, the higher the plant population and the higher the yield per hectare.
If weed control is by cultivation, wider row spacing is required.
We shall look at other aspects of soyabean production in the next series of articles.