Cassava is a tropical crop growing mainly in the West and East of Nigeria, though some varieties could grow in the middle belt. Nigeria is the leading producer of cassava in the world. Both roots and leaves could be eaten. Flour can also be made from cassava. Cassava is propagated vegetative by stem cuttings. The root yield of improved genotypes (varieties) is substantially more than local genotypes under a wide range of climatic, intercropping and intensification conditions, even without the use of improved inputs such as fertilizers. The yield gap increases in favour of improved genotypes when best management practices are used.
The improved varieties also perform better than local genotypes in terms of early bulking. They can attain maximum root yield at 13-15 months after planting (MAP) and the yield is stable for above 24 MAP. The local genotypes in the other hand do not reach maximum bulking before 22-24 months after plating.
Improved cassava production in Nigeria is labour intensive and generally concentrated on small family farms of less than 3 hectares. Growing population pressure and reduced fallow period make cassava an increasingly important crop because of its ability to tolerate nutrient poor soils.
The cost of production of cassava varies throughout the country.
HOW DO YOU SELECT A GOOD SITE FOR PLANTING CASSAVA.
Cassava grows best in areas with deep, well drained loamy soils with good rainfall and warm, moist (not dry) weather. The factors that will assist in selection of the area well include: vegetation in the area, soil type and richness, and land type: flat or sloppy.
Area with thick vegetation is best ideal
Sites with dense vegetation cover will have rich [fertile] soils. Reason: thick vegetation protects the soil from direct sunlight which reduces water that is lost from the soil. It also reduces erosion (i.e water percolation increases). The vegetation also drops a lot leaves which decay and give food (nutrients) to the soil. The dead leaves will bring in earthworms and other soil organisms which help to increase the amount of air in the soil.
Area with good soil texture should be chosen
The best soil for cassava is deep, loamy soil because it has good food (nutrient) and low in gravel. It also holds water very well, and it is easy for ridges or mounds making.
Identifying a good loamy soil.
Put a small amount of water on a small soil, try to shape/turn it into a ball. If you press the ball and it falls apart them the soil is loamy. If it is gritty (hard) and you can not shape it into a ball it is sandy soil. But if you shape it into a ball and the soil does not break/fall apart when pressed, then it is a clay soil. Sandy and clay are not good for cassava.
An area with fertile soil is best ideal
Good (fertile) soils will have a dark colour (dark brown or dark red). The dark colour shows the soil has a lot of organic matter (food). Do not grow cassava on waterlogged soil (areas with too much water on the ground).
Source an area with flat or gently sloppy
The best farm land for cassava is flat or gently sloping. Too sloppy land is not good, because the top soil is easily washed away. Valleys are also not good because they have too much water and will not allow the cassava roots to develop well. Quick maturing varieties may however be planted on mounds or ridges in inland valleys during the dry season.
Selecting the cassava varieties to plant?
The best cassava plants are:
– those which grow fat;
– those which give good yield;
– those which store well;
– those that are tolerant to pests and diseases;
FACTORS THAT GUIDE IN THE SELECTION
Cassava with high gari quality.
Cassava type whose storage roots have 30% or more dry matter are good. They give good quality products and are profitable for growers and market women.
Cassava type with good mealiness
Mealiness refer to the cooking ability of cassava storage roots without processing it. Mealy variety are called sweet-cassava while non-mealy type are called bitter cassava which has to be processed before eaten.
Cassava that mature (bulk) early
Cassava that mature early are better because they are able to offset losses in yield caused by weed competition, leaf-feeding pests and diseases than the late maturing ones.
Cassava that store well in the ground
Source for those cassava which will stay longer in the soil without going bad. This helps to spread the period of harvest and reduces the problem of processing and storage of fresh roots.
Cassava that can fight weeds, pests and diseases
Some cassava type tolerate weeds, pests and diseases than others. For example if weeds are a problem source for cassava which branch early, and often such type develop faster and have lot of branches and leaves which shade the ground and prevent weeds from growing too much.
Selecting healthy cassava stem cuttings?
Most common way is from farmers’ farms or at village or town markets or from government agencies e.g the ADP. Most of the cassava pests and diseases are spread by the distribution of infested planting materials. Therefore use very clean cuttings for plantings. In sourcing your planting materials look at cassava plant with the following:
(a) Select in the farm healthy/cassava plants with robust stems and branches, good leaves not damaged by pests and diseases. The soft top green or hard bottom are not good because they dry quickly, produce unhealthy sprouts and are easily damaged by pests and diseases;
(b) Avoid plants already infested with pest and diseases
Position of Cuttings
Cassava cuttings could be planted in three ways.
(a) Vertical: place 2/3 of the cuttings in the soil
(b) At an angle: also place 2/3 of the cuttings in the soil.
(c) Horizontal: Place the entire cutting horizontally in the soil at a depth of 5 – 20cm
Cutting position affects growth. How?
- Vertical planting sprout and develop foliage quicker than cuttings planted at an angle or horizontal
- Vertical plantings produces deeper roots than angled planting roots of horizontal planting are very close of the soil surface and can be destroyed by rodents and birds.
iii. Roots from vertical or angled planting are arranged more compactly and are difficult to harvest than horizontal planting.
- In horizontal planting, several weak stems may develop, but it has the advantage of killing insect and mite pests which occur on cutting surface.
Soil Type and Orientation of planting.
In clay soil, plant angle, vertical or horizontal because water is adequate but in a sandy soil use vertical and let 2/3 of the cuttings be buried in the soil to touch water. In loamy soil, it is good to plant at angle.
Plant early just before the rains start or after the rains begin. Delayed planting leads to reduced yield. When planting is done early, cuttings sprouts, establish well and receive good water and able to withstand diseases and pests late in the season. Late planting at the end of rain season exposes cassava to damage by pests and diseases and dry period.
In dry sandy soil, shallow planting at low water level leads to poor growth and yield. Plant cassava cuttings deep in moist soil; and in heavy soils, plant shallow. Deep planting makes harvesting difficult but in areas of termite infestation, plant deep.
Spacing and Plant Density
This depends on whether cassava is grown alone or with other crops. If cassava is grown alone, plant 80cm – 100 cm apart from each other. This gives 15,000 stands per hectare. If cassava is to be grown with other crops, consider the branching system of both cassava and other crops and have enough space for the plants. Also leave enough space for you to work between the plants during weeding and other activities. Then use a spacing of 1m X1m to give 10,000 plants per hectare.
Land is usually prepared mainly to loosen up the soil, improve water movement in the soil and allow for roots to develop well. Mounds or ridges could be used; ideal for good roots development and protecting the storage roots from rodents and birds. However, plating can also be done on a flat land. Best soil is loamy soil.
Preparing the Cutting
Cuttings should be 20 – 25 cm long with about 5 – 8 nodes. Handle cuttings carefully during transportation to prevent bruises and damage to the growing points. This is done by packing them on cushion of dry leaves.
If the cuttings are infested with cassava green mites, mealy bugs or other pests, the cuttings can be treated by immersing them in heated water for 5 – 10 minutes just before planting. This will kill pests on the surface of the cuttings. You can prepare the heated water by mixing equal volumes of boiling and cold water or deep the cuttings into a dilute solution of 1% rogor. To kill stem pest or anthracnose and other fungal use Decis or Benlate.
Slow growth of the planted cuttings makes cassava to be attacked by weeds in the first 3 to 4 months. Though early branching varieties develop shade faster which helps to control the weeds.
Weed competing with cassava reduces canopy formation and root formation. This could be about 40% in early branching cultivars to 70% in late or non branching cultivars. When cassava does not fully shaded the ground, weeds problem is more obvious.
- Grasses: Elephant grass, Guinea grass, Andropogron and spear grass.
- Broad leaves – Chromolaena spp, mucuna spp, and mimosa spp.
Spear grass is bad because it also pierces the roots of cassava allowing for root rot causing pests to penetrate the root.
Control of weeds
Weed by hand at 3, 8 and 12 weeks after planting
(a) Plant mucuna during the season before cassava cultivation. Cassava cultivation can be planted directly into the mulch cover with little or no land clearing.
(b) Use chemical e.g Diuron (1-3 kg 1ha), Chloramben (1-3 kg 1ha), Metolachlor (49 1ha), Primextra (2-3kg/ha)
Herbicide is most effective if it is applied before weeds infest a field. If planting or weed control is delayed until weeds occur, then mix emergence and contact herbicide e.g. ‘Basta’. It is cheap to apply herbicide on large cassava farm to control weeds than manual weeding.
Cassava is popular because of its ability to grow in poor soil. Cassava renders the soil poor faster, therefore nutrients have to be replaced fast. The cassava roots are many and tap nutrients from expanse of soil area. In such condition yields could be between 7 and 10 tones per hectare. However on a good soil, yields could be as high as 40 – 60 tonnes per hectare. Apply between 400 – 600 kg of fertilizer (i.e 8 – 12 bags) per hectare.
Harvest the cassava roots between 7 (early type) and 12 months (late type) after planting depending on the type, when there is good amount of starch but not too late
when the roots become woody. Though most cassava varieties attain the best weight at about 18 months when the starch accumulation is highest.
Harvesting is done manually, by cutting the stems a few centimeter above the ground with a cutlass. Then loosen the soil around the roots, and pull the stub of the stem to lift out the roots. Harvesting is easier when soil is moist. Harvesting is also easier if planting is done on ridges or on beds and in loose or sandy soils, rather than on flat ground and in clay or heavy soils.