Fertiliser has become a big part in a farmer’s operations and budget because the correct and right quantity of fertiliser will give a farmer a better yield. It is recommended that where available, both organic (like manure and compost) and inorganic fertiliser should be applied to small grains.
Manure and basal fertiliser application
Ideally, the quantity of fertiliser and lime to apply should be determined through soil testing. However, as a rule the recommended rate of basal fertiliser application for optimal yields is 200 kg/ha. Basal fertiliser should always be applied before or at planting, under the seed, making sure that it does not get into direct contact with the seed. This is achieved by covering the fertiliser with a layer of soil (1 cm thick) before seeding.
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- Granular fertiliser
The different methods of manure and basal fertiliser application:
Basin method
- Apply one to two handfuls of wellrotted manure/compost in each basin and mix with the soil. • Apply two heaped beer bottle caps (equivalent of 200 kg/ha) of basal fertiliser per basin.
Ripper-tine method
- Apply one to two handfuls of wellrotted manure/compost over 30 cm along each planting line/furrow.
- Apply two heaped beer bottle caps (equivalent of 200 kg/ha) of basal fertiliser over 30 cm along the furrow/planting line.
Conventional method
- Apply one to two handfuls of wellrotted manure/compost over 30 cm along each planting line/furrow.
- Apply two heaped beer bottle caps (equivalent of 200 kg/ha) of basal fertiliser over 30 cm along the furrow/planting line.
Top dressing
The generally recommended top dressing application rate is 150 kg/ha. Yields have been shown to increase as more fertiliser is applied to the crop up to a maximum of 150 kg/ha. In sandy soils and when there is a lot of rainfall, split application of top dressing is recommended. The desired amount of top dressing is split into two, with half the quantity applied at the five to six leaf stage and the other half at flowering. When applying top dressing, avoid getting the fertiliser into contact with the plant because this may result in the fertiliser burning the plant.
Basin method
- Apply N fertiliser at the five to six leaf stage (four to six weeks after crop germination), using one level beer bottle cap per basin, and another one two weeks later (depending on moisture regime). The two beer bottle caps total 150 kg/ha.
- Top dressing must be done when the soil is moist, preferably soon after raining.
Ripper-tine method
- Apply N fertiliser at the five to six leaf stage (four to six weeks after crop germination) using one level beer bottle cap per two plants two weeks later (depending on moisture regime). The two beer bottle caps total 150 kg/ha.
- Top dressing must be done when the soil is moist, preferably soon after raining.
Conventional method
- Apply N fertiliser at the five to six leaf stage (four to six weeks after crop germination) using one level beer bottle cap per two plants, and another one per two plants two weeks later (depending on moisture regime). The two beer bottle caps total 150 kg/ha.
- Top dressing must be done when the soil is moist, preferably soon after raining.
Planting time
The best time for planting is as soon as the first effective rains (when there is enough moisture in the soil for seed germination) have been received. The time when the first effective rains are received varies from place to place and has become quite unpredictable with the current changes in the rainfall pattern and drought. Conservation farming ensures early planting since the field is prepared prior to the rains. Planting basins or furrows concentrate water, creating a conducive moisture regime for seed germination.
Planting methods
The planting options are highlighted below:
Basin method:
- Plant five pips per basin
- Cover the seeds with two to three cm of clod-free soil
Ripper-tine method:
- Drill the seed thinly in the planting furrow so that individual seeds are 10 to 15 cm apart for sorghum and pearl millet, and 5 to 10 cm apart for finger millet.
- Cover the seeds with two to three cm of clod-free soil.
- Seeds can also be drilled using a direct seeder calibrated for the particular crop.
Conventional method:
- Drill the seed thinly in the planting furrow so that individual seeds are 10 to 15 cm apart for sorghum and pearl millet, and 5 to 10 cm apart for finger millet.
- Cover the seeds with two to three cm of clod-free soil.
- Seeds can also be drilled using a direct seeder calibrated for the crop. Some farmers have used traditional methods of planting small grains such as the broadcasting and seedbed methods. Under the broadcast method seed is broadcast evenly onto prepared land (conventionally tilled). To help evenly distribute the seed over the land, the seed may be mixed with dry river sand.
After broadcasting the seed is covered with soil by either running a branch, or an ox drawn harrow over the planted land. In some cases, farmers drive a herd of cattle at a fast speed over the planted land. Although the broadcast method is very quick, there is a risk of the seed being covered by too much soil, which may inhibit emergence of the seedling. Weeding, thinning, harvesting and other field operations are difficult to carry out. This method is generally not recommended.
Thinning
Thinning is very important to ensure the optimal plant population. A plant population that is higher than optimal will result in tall and thin plants that will produce very small heads, resulting in reduced yields. On the other hand, a lower than optimal plant population will result in fewer heads, resulting in reduced yields.
Thinning guidelines are indicated below:
Basin method:
At two to three weeks after germination or at the three to four leaf stage, uproot the weakest and leave the two strongest plants per basin. If the soil moisture is favourable, the uprooted plants can be transplanted. The resultant average number of plants per basin should be two.
Ripper-tine method:
At two to three weeks after germination or at the three to four leaf stage, thin by uprooting to the recommended spacing for each crop as shown below:
- Sorghum: 20 cm between plants in a row
- Pearl millet: 15 cm between plants in a row • Finger millet: 10 cm between plants in a row The removed plants can be transplanted provided the soil moisture is favourable.
Conventional method: At two to three weeks after germination or at the three to four leaf stage, thin by uprooting to the recommended spacing for each crop as shown below:
- Sorghum: 20 cm between plants in a row
- Pearl millet: 15 cm between plants in a row • Finger millet: 10 cm between plants in a row The removed plants can be transplanted provided the soil moisture is favourable
Weeding
The first weeding should be done as soon as weeds start to emerge. Young plants must be kept weed free for the first 45 days of growth, and so weeding should be repeated as many times as is necessary to keep the crop weed free for this period. Late weeding is also recommended so that the crop is weed free at the time of harvesting. Appropriate use of herbicides will ensure a weed free crop. Use of pre-emergence herbicides like atrazine recommended in soils with higher than 25% clay content.
In the next edition we shall discuss pest and disease management.
We thank the Zimbabwe government and the Food and Agricultural Organisation of the United Nations for the use of this guide.
