What you need to know:
- Cassava cuttings should be obtained from mature stems from plants that are nine to 18 months, long enough with at least five nodes.
- In mono-cropping, the recommended spacing is a square arrangement, 1m by 1m giving 10,000 plants per hectare or 4,000 plants per acre.
- According to Dr Munga, cassava is a hardy crop and has an extensive root system that enables it to grow in poor soils.
- Harvesting can be mechanically done using a pull harvester attached to a tractor.
With six new varieties that mature in about eight months now available, growing cassava should not be a tedious task.
Dr Theresia Munga, the Kenya Agricultural and Livestock Research Organisation (Kalro) director of industrial crops at Mtwapa centre, says the new varieties are Shibe, Karembo, Tajirika, Siri, Nzalauka and Karibuni.
“These varieties mature in eight to 12 months and have the potential of producing up to 28 tonnes per acre. They produce high-yield cassava that can stay for up to 24 months in the soil after maturity without going bad,” she says, adding they are resistant to cassava brown streak virus and cassava mosaic virus.
But how does one ensure they get maximum yields from the crop?
“Land preparation is key,” says Dr Munga. “This is done to remove weeds and incorporate biomass into the soil to ensure good establishment of the cassava cuttings. It also facilitates initial root penetration and thickening, easier harvesting, and higher yields,” she says.
The ploughing should be done to a depth of 15 – 30cm, followed by harrowing to a depth of about 10cm, says Dr Munga.
“One can use herbicides to eliminate weeds or in less weed-infested fields, a farmer should simply slash and till by hand, oxen or tractor.”
For land that has a leguminous cover crop such as soy bean, pigeon pea or peanut, a farmer can plough the cover crop biomass into the soil or retain it as mulch on the soil surface to increase soil organic matter.
Cassava cuttings should be obtained from mature stems from plants that are nine to 18 months, long enough with at least five nodes, she says.
In mono-cropping, the recommended spacing is a square arrangement, 1m by 1m giving 10,000 plants per hectare or 4,000 plants per acre.
“Non-branching varieties like Siri may be grown in a higher density of 1 metre by 0.5 metres. For seed production, a spacing of 0.5 by 0.5 metre can be used. While intercropping, the recommended planting density is 10,000 cassava plants. Where one plant – maize, for instance – is to be planted, it should be done 20cm apart between cassava rows,” says the scientist.
The cuttings are planted at an angle of about 45 degrees into the soil. “It is advisable to plant cassavas at the onset of long-rain seasons in March to April.”
According to Dr Munga, cassava is a hardy crop and has an extensive root system that enables it to grow in poor soils. It draws a large number of nutrients like nitrogen (N), potassium (K) and phosphorus (P) from the soil.
Dr Benjamin Kivuva, a crop production and seed scientist at Kalro, Nairobi, notes that due to the nature of the crop, fertiliser should not be applied during heavy rains when the soil is too wet or waterlogged.
“Inherent soil fertility can fulfil nutrient requirements of cassava varieties that produce 10 tonnes per hectare. But NPK fertiliser with 20 nitrogen, 1.8 phosphorous and 13.8 potassium can be used for every extra tonne of tubers.”
Easier to harvest
Cassava is prone to weed competition in the first three to four months.
“Therefore, the first weeding should be within the first month of planting and should be repeated at eight and 12 weeks depending on weed pressure,” explains Dr Munga, noting weeding is done manually using hoes or cutlass.
Final weeding should be done between 20 and 24 weeks after planting, she offers, adding that radial cracking of the soil around the stem is an indicator of maturity.
Harvesting can be mechanically done using a pull harvester attached to a tractor.
But for the small farmer, it is easier to harvest cassava when it is planted on ridges, in loose or sandy soils or during wet the season, where the crop is pulled out.