PREPARATION OF PLANTING MATERIALS
Use sharp tools preferably a secateurs or cutlass to cut stems into stakes for planting. Avoid bruising the stems. Smooth cuts enhance root yields through rapid and uniform root development from the cut surface. The recommended length of stakes is 20-25 cm with 5 or more nodes. Mini-stakes (10 cm) are required for multiplication while micro-stakes (3-5 cm) are used for rapid multiplication.
HANDLING OF STAKES
Stakes should be planted soon after they are cut otherwise they get dehydrated and perform poorly. If stakes must be stored for a few days (3-5 days) before planting put them into transparent polyethylene bags. You can also gather the stakes together under shade and cover with a plastic bag. The high relative humidity and temperature within the bag usually induce rapid sprouting and rooting of stakes. Plant vigor, survival rate and yields are better if stakes are pre-sprouted before planting.
TIME OF PLANTING
Planting should be done as soon as the rains become steady in your area. This varies from March to November in the rain forest, April to August in the derived savanna, May to July in the Southern Guinea savanna (SGS) and July to August in the Northern Guinea savanna (NGS).
METHOD OF PLANTING
Stakes can be planted vertically (buds facing up with 2/3 of the stake in the soil), horizontally (whole stake buried 3-5 cm in the soil) or inclined (buds facing up with 2/3 of the stake buried in the soil at an angle of about 45o). When stakes are planted vertically tuberous roots bulk deep into the soil. Although this gives more stability to the plant against lodging, it makes harvesting very difficult. This orientation is recommended for sandy soils. Stakes planted horizontally produce multiple stems and more tuberous roots but they are comparatively smaller in size. The roots are produced near the surface and they are easily exposed to mechanical damage and to rodents. However, in loamy and rich soils the multiple stems and roots are at an advantage resulting in high yields.
Stakes that are inclined on the ridge produce tuberous roots in the same direction. The inclination of the stem and roots provide a leverage which
makes harvesting easier than in the other orientations. In shallow and clayey soils, stakes should be inclined. In the rain forest and derived savanna, farmers incline their stakes at planting.
The optimum plant population for high root yield is 10,000 plants per hectare obtainable when plants are spaced at 1 x 1 m. This population is seldom achieved at harvest due to losses caused by genetic and environmental factors. In other to harvest a plant population near the optimum an initial plant population/ha of 12300 at 0.9 x 0.9m is recommended. Plant spacing and population will vary depending on if cassava is planted sole or in association with other crops.
Cassava is compatible with many crops when intercropped. The best intercrops of cassava in Nigeria include maize, melon, groundnut, cowpea and vegetables. Other less important intercrops particularly in the South-south and Southeastern Nigeria include yam, cocoyam, sweet potato, plantain and banana. Non or high branching varieties of cassava are best for intercropping. Profuse and low branching varieties will shade light off the intercrops. In medium and large-scale farms maize is the best intercrop.
This is one of the major limiting factors to production accounting for more than 25% of the total cost and time of production. Integrated weed control (cultural, mechanical and chemical) is recommended. The ideal combination will depend on the agro-ecology, weed spectrum and level of infestation, soil type and cropping system.
Plant early before weeds emerge after land preparation. Adopt improved fallow practices using Mucuna pruriens and live mulch using melon to suppress weeds. Under monocropping, plant varieties with potentials for early canopy closure to reduce weed infestation. Such varieties should be vigorous and resistant to major pests and diseases in addition to having multiple branching at a medium height.
Do double or triple harrowing before planting. Weed with hoes or adapted cutlasses 3 or more times depending on agroecology and type of weed. More weeding times is required in the forest than in the savanna. Weeds with stolon, rhizome, tubers or deep taproot require more frequent weeding. On a large scale you will require tractor operated weeders.
Several pre and post emergence herbicides exist but only few of them are available in Nigeria for controlling weeds in a cassava farm. In the forest zone apply pre-emergence herbicides like premextra or dual while in the savanna zone you can apply primextra, dual or cotoran multi immediately after planting to keep your farm weed free for periods ranging from 4-8 weeks. Consult manufacturers’ labels for guidelines and follow the rates specified for each chemical. Apply post-emergence herbicides (paraquat or gramozone) as soon as weeds begin to emerge after the pre-emergence herbicide treatment.
SPRAYING OF INSECTICIDES ON CASSAVA FARM
They are basically non-selective, localized contact herbicides and should be sprayed with a guard to ensure that only the weeds receive the chemical. If your field is infested with difficult-to-control weeds like Spear grass (Imperata cylindrica) carefully apply systemic herbicides like Glyphosate, Fusilade or Sarosate. Follow the manufacturers’ guidelines for each of the herbicides. Weather conditions affect herbicide performance. Do not apply herbicides soon after a heavy rainfall or when it is likely to rain to avoid diluting the chemical and reducing its effectiveness. For best results gramozone should be sprayed only when you are sure of having at least 3 hours of sunshine after spraying. For cost effectiveness and results use skilled staff for chemical weeds control.
FERTILIZER RATE AND TIME OF APPLICATION
Ideally, fertilizer recommendations should be based on soil analysis but when this is not done then use the land history and vegetation as a guide.
Lands naturally inundated with Chromolaena odorata (Akintola taku) as weed can support a good cassava crop without fertilizer while the presence of Spear grass or poorly established vegetation is a signal for fertilization. Under continuous cultivation in the forest zone apply a first dose of 200kg (4 bags) of N: P: K 15:15:15 per hectare or a full small matchbox per plant at 4-6 weeks after planting (June-July). A second dose of 100kg of muriate of potash or a half-full small matchbox per plant at 14-16 weeks after planting (September) should also be applied. In the savanna zone, apply 200kg (4 bags) of N: P: K 15:15:15 per hectare or a full small matchbox per plant at 4-6 weeks after planting and a second dose of 50kg of muriate of potash per hectare. Apply fertilizer in holes 5 cm deep and 10 cm radius from the plant. Do not apply fertilizer if the soil is dry.