Agricultural Science · Lesson 5

Crop classification, propagation, cropping systems and husbandry of major crops

JAMBWAECNECO

What the syllabus asks

JAMB: B5 plant forms and functions, B6 plant propagation, B7 cropping systems, B8–B9 husbandry of selected crops, B10 pasture and forage, B11 floriculture

WAEC: D1 Classification of crops; D2 Husbandry of major crops (cereals, legumes, roots and tubers, vegetables, fruits, beverages, oils, fibres, spices, latex); D3 Pasture and forage crops; F Floriculture/ornamentals; Practical C1, C3, C4, C6

NECO: D1 Classification of crops; D2 Husbandry of major crops (cereals, legumes, roots and tubers, vegetables, fruits, beverages, oils, fibres, spices, latex); D3 Pasture and forage crops; F Floriculture/ornamentals; Practical C1, C3, C4, C6

What you will learn

Classify crops by life cycle, use and botanical form.
Describe sexual and vegetative methods of propagation, including budding, grafting and layering.
Explain cropping systems and their merits.
Describe the husbandry of a cereal, a legume, a root/tuber crop, a vegetable and a tree crop.
Calculate plant population and seed requirements.
Describe nursery practice and transplanting.
Describe establishment and management of pasture.
Outline the importance and care of ornamental plants.

Key points

Crops are classed by life cycle, by use, and by botanical form.
Good seed: viable, true to type, clean, healthy, mature, certified.
Germination % = germinated ÷ sown × 100.
Vegetative propagation: cuttings, setts, suckers, layering, budding, grafting, tissue culture.
Vegetative offspring are true to type but carry viruses.
Cropping systems: sole, mixed, intercropping, relay, rotation, alley, bush fallow.
Rotation: include legumes, alternate root depths, avoid same family in succession.
Plant population = 10 000 ÷ (row × stand spacing in m) × plants per stand.
Maize 75 × 25 cm = 53 333 plants/ha; oil palm 9 m triangular = about 143/ha; cocoa 3 × 3 m = 1 111/ha.
Lowland rice is nursed, transplanted, puddled; parboiling reduces breakage.
Legumes fix nitrogen; groundnut pegs need loose soil; cowpea needs heavy pest control.
Yam: setts/minisetts, heaps, staking, barns; cassava: stem cuttings, process within days into garri.
Nursery: site, beds/bags, shade, water, harden off, transplant in the evening.
Cocoa beans are fermented then dried; Tenera oil palm gives the most oil.
Pasture: grass + legume mixtures, rotational grazing, hay and silage for the dry season.
Ornamentals: hedges, lawns, flowers, avenue trees; beauty, shade, income.

Start here: Classification of crops

A farmer in Kaduna may grow maize, sorghum, cowpea, groundnut and pepper in one season, while her cousin in Ondo tends cocoa, oil palm, plantain and cassava. To study these crops we group them. Each grouping answers a different question: how long does the crop live, what is it used for, and what kind of plant is it?

1. By life cycle

Annuals complete their life cycle in one season: maize, rice, sorghum, millet, cowpea, groundnut, soya bean, okra, tomato, melon (egusi).
Biennials take two seasons: vegetative growth in the first, flowering and seed in the second, e.g. onion and carrot when grown for seed. In Nigeria most such crops are harvested in the first season for their bulbs or roots.
Perennials live for many years: cocoa, oil palm, rubber, kola, cashew, citrus, mango, coffee. Some crops such as cassava and pigeon pea are perennials grown as annuals.

2. By use (agricultural classification)

Class	Nigerian examples	Main product
Cereals	Maize, rice, sorghum (guinea corn), millet, wheat, acha (fonio)	Grain (carbohydrate)
Legumes (pulses)	Cowpea, groundnut, soya bean, bambara nut, pigeon pea	Protein-rich seeds; oil (groundnut, soya)
Roots and tubers	Yam, cassava, cocoyam, sweet potato, Irish potato (Jos Plateau)	Carbohydrate
Vegetables	Tomato, pepper, okra, amaranth (green), fluted pumpkin (ugu), onion	Vitamins, minerals
Fruits	Orange, mango, pineapple, pawpaw, banana, plantain, cashew apple	Vitamins, sugars
Beverages and stimulants	Cocoa, coffee, tea (Mambilla), kola	Drinks, stimulants
Oil crops	Oil palm, groundnut, soya bean, coconut, sesame (beniseed), shea	Vegetable oil
Fibres	Cotton, kenaf, jute, sisal, raffia	Fibre for textiles, sacks, ropes
Latex	Rubber (Hevea brasiliensis)	Latex for rubber goods
Spices	Ginger (southern Kaduna), pepper, garlic, turmeric	Flavouring
Sugar	Sugarcane	Sugar
Forage	Guinea grass, Stylosanthes, Centrosema	Livestock feed

3. By botanical form

Monocotyledons: one seed leaf, parallel veins, fibrous roots: maize, rice, yam, oil palm, onion, sugarcane.
Dicotyledons: two seed leaves, net veins, tap roots: cowpea, cassava, cocoa, tomato, cotton.
Growth habit: herbs (amaranth), shrubs (cassava, cotton), trees (mango, cocoa), climbers (yam, passion fruit), creepers (melon, sweet potato).

Worked example 5.1

Classify each crop by use and by life cycle: (a) cocoa (b) cowpea (c) cotton (d) yam.

(a) Beverage; perennial.
(b) Legume (pulse); annual.
(c) Fibre (also oil from seed); grown as an annual.
(d) Root/tuber crop; grown as an annual (the plant can persist, but it is replanted each year).

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Practice questions

1. Which of these is a perennial crop?

cocoa
maize
cowpea
okra

Show answer

A: cocoa
Perennials live for many years.

2. Crops grown mainly for their fibre include

yam and cassava
cowpea and soybean
maize and sorghum
cotton and jute

Show answer

D: cotton and jute
Others: kenaf, sisal.

3. A farmer sows 200 seeds and 170 germinate. The germination percentage is

Show answer

C: 85%
170 ÷ 200 × 100 = 85%.

4. Maize planted at 75 cm × 25 cm with one plant per stand gives how many plants per hectare?

106,667
53,333
5,333
26,667

Show answer

B: 53,333
10,000 ÷ (0.75 × 0.25) = 53,333.

5. Joining a scion to a rootstock is

grafting
layering
budding only
marcotting

Show answer

A: grafting
Budding uses a single bud as the scion.

Key words

Annual crop: A crop that completes its life cycle in one season or year, e.g. maize, cowpea.
Biennial crop: A crop that completes its life cycle in two years, flowering in the second, e.g. onion grown for seed.
Perennial crop: A crop that lives for more than two years, e.g. cocoa, oil palm, citrus.
Cereal: A grass crop grown for its edible grain, e.g. maize, rice, sorghum, millet.
Legume: A plant of the pea family whose root nodules host nitrogen-fixing Rhizobium bacteria; seeds borne in pods.
Propagation: The multiplication of plants by seed or by vegetative parts.
Sett: A piece of yam tuber used for planting; a miniset weighs about 25 g.
Seed rate: The quantity of seed needed to plant a unit area, e.g. kg per hectare.
Spacing: The distance between rows and between plants within a row.
Thinning: Removing excess seedlings so that the right number remains per stand.
Supplying: Replanting stands where seeds failed to germinate.
Intercropping: Growing two or more crops together on the same land in a definite row pattern.

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