Discuss five agronomical practices of cassava cultivation

1.Selection of varieties for breeding
i. Disease free
ii. Tuber yield
iii. Hydrocyanogenic acid (HCN) contents
iv. Maturity
v. Plant height especially in intercropping
- Usually the varieties are categorized in the basis of HCN concentrations namely sweat and bitter varieties. Sweat variety has low HCN contents which is restricted to the skin of the cassava tubers. The bitter variety has high HCN contents which is distributed throughout the tuber with the highest concentration is in the inner fibrous core.
-Many farmers grow bitter variety than sweat variety susceptible to pests like rodents, monkeys
-There are a number of clones grown locally under different names
-Improved clones are being made available to farmers such as Kibandameno, Mucericeri, Adhiambolera.

2.Land preparation
-Done mechanically by oxen drown or tractor drown ploughs
Two systems of preparation:
i. Ridges
ii. Flat ground
-Planting on flat ground is the common method but plants are earthed up during weeding. This control weeds around the plant and also improves drainage around the plant. Flat planting is less expensive than ridge planting.
-Earthling also give tubers enough space for growth and thus encourage tuber expansion and also make harvesting easy.
-Ridges are used in soils which are water logged
-The planting material used are stem cutting ranging in size 20-25cm long and 2.5 -4.0cm thick and each must have a bud (eye)
-The cutting is placed slanting at 450 with the bud facing upwards in the soil of poor drainage to avoid rooting of buds.
-Cuttings can also be laid flat in a furrow which is about 70 -90 cm deep and cover with soil. -This is done in light soil with good drainage

3.Cropping systems
Three main types
i. Monocropping
ii. Intercropping
iii. Rotations

i. Monocroping
-Growing as pure stand
-Most distinctive factor is maintenance of distinctive rows and plant population. Stems are planted in rows at spacing of 1.5m x 0.9m or 1.0m x1.om giving plant population of 10000-30000plants/ha.
-Plant population is not a very critical for cassava production as it has high potential for forming branches and increase number of tubes. Thus it has wide spacing range. Crops with small spacing range are very sensitive to plant population.

ii. Intercropping
-Cassava can be intercropped with annual or perennials crops such as sweet potatoes, maize, beans, legumes,
-If intercropped with perennial crops it should be established on the 1st of the establishment of the perennial crop. This help in weed management.

iii. Rotation
-Cassava is mainly grown in rotation with leguminous plants. It can be used either at the end of fallow period (There is reduced yields in cereals if planted immediately after fallow period due to microbial degradation of excess organic matter immobilizing the soil nitrogen reducing availability of nitrogen)Thus cassava is planted to give soil time for microbial degradation of organic matter. Also cassava has low usage of nutrients in the soil. Thus survive during microbial degradation of high organic matter and nitrogen immobilization and slow nitrogen content of the soil.

4.Planting Time
-Should be done early at the onset of rain. However this is not very critical particularly where the soil has high water holding capacity.
-Also in many farming situations farmers put priority on cereal crops and legumes thus plant cassava late.

5.Fertilizer Application
-It is recommended not to apply fertilizer or manure to cassava crop. This because from experiments, the response to fertilizer is erratic and even where there is positive response the magnitude of response is small (that is small increase in yield thus not worth fertilizer application).
-Secondly, no money to use in fertilizer as farmers put interest in other crops.
-Manure is not recommended as they are not available, are expensive and finally lock of nitrogen in microorganisms which starts mineralization of manures.
-Use of manures and fertilizers also results in increased vegetative production but reducing tuber growth and yield.
-Can only apply a little of nitrogen and phosphates as a starter fertilizer.

6.Weed Control
--Mostly perennial grasses and nut sedges.
Weed control should be started early in the establishment of the plant. The first 8 -16 weeks are very critical for development as plants grow slowly at this period and hence clean weeding is required.
-Experimental results in weeding frequency have shown that weeding should be done at least 3 times before a complete canopy cover (16 weeks after planting).
-After development of complete canopy cover no need to weed any more
-Weeding is mostly manual. This is because cassava plants have very superficial root system which can be damaged by mechanical weeding implements resulting in reduced yields.

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Titany answered the question on August 16, 2021 at 11:56