Introduction to Agriculture
Senior 1 · Agriculture
Introduction to Agriculture
Lesson 4 of 4
24 min
Let's begin
In parts of Central Africa where people are few and forest is plentiful, a family may clear a patch of forest, farm it for two or three years, then move on and let the forest grow back. In Rwanda, with about 14 million people on 26,338 km² (Wikipedia estimate, read September 2026), that is impossible: there is simply no spare land to move to.
Which farming system suits a place depends on how much land there is, the rainfall, the soil and the market. This lesson looks at five more systems and at how crops are arranged in a field.
Shifting cultivation is a system in which a plot is cleared, often by slashing and burning the vegetation, cropped for a few years until the soil is exhausted or weeds take over, then abandoned so that natural vegetation can restore its fertility while the farmer moves to a new plot. In bush fallowing (land rotation) the family stays in one home and rotates its fields around it.
| Advantages | Disadvantages |
|---|---|
| The fallow restores fertility with no fertiliser | Needs a very large area of land per family |
| Few inputs and little capital | Destroys forest; burning kills soil organisms and wastes organic matter |
| Pests and diseases die out during the fallow | Bare, burnt soil erodes easily |
| Low yields; no permanent investment in the land |
Nomadic pastoralism is the herding of livestock from place to place in search of pasture and water. When the moves follow a regular seasonal pattern between fixed pastures, it is called transhumance. It suits dry lands where crops fail, but herds can overgraze and spread disease, herders may clash with farmers, and children find it hard to attend school.
Ranching is the commercial rearing of grazing animals, mainly beef cattle, on a large fenced area divided into paddocks. The rancher controls grazing, dips or sprays against ticks, vaccinates and breeds for high output. In Rwanda, ranches are found mainly in the drier east, such as Nyagatare District. Ranching needs a lot of land and capital, but produces much meat and milk for the market with little damage to pasture when grazing is rotated.
Plantation farming is the growing of one cash crop on a large estate, usually with its own factory, many workers and scientific management. Tea estates in Rwanda's high, rainy areas are the clearest example; neighbouring smallholders often grow tea too and sell their green leaf to the estate factory.
| Advantages | Disadvantages |
|---|---|
| Earns foreign exchange | Needs huge capital |
| Employs many people | One crop: a price fall or a disease can ruin the estate |
| Produce is processed on site, so quality is high | Takes land that could grow food crops |
| Builds roads, clinics and schools near the estate | Continuous single cropping needs heavy fertiliser use |
Agroforestry is a land-use system in which trees or shrubs are grown deliberately together with crops, livestock or both on the same land. On Rwandan farms you will see Grevillea trees along terrace edges, fodder shrubs such as Calliandra and Leucaena on the risers, and avocado or mango trees around the homestead.
Question: A family needs to crop 1 ha every year. Under shifting cultivation each plot is cropped for 2 years and then left fallow for 10 years. (a) How much land must the family control? (b) Compare this with a Rwandan smallholding of 0.5 ha (an illustrative size).
(a) One full cycle for a plot = 2 years cropped + 10 years fallow = 12 years. Each plot is cropped for only 2 of those 12 years, so the family needs 12 ÷ 2 = 6 plots of 1 ha each, that is 6 ha.
(b) 6 ha ÷ 0.5 ha = 12. The family would need twelve times the land a typical smallholder has. This is why Rwandan farmers must keep the same land fertile with manure, rotation and terraces instead of leaving it to rest.
Tip
Memory hook: "Move the field, move the herd, fence the herd, one-crop estate, trees in the farm" gives the five systems in order: shifting cultivation, nomadic pastoralism, ranching, plantation farming, agroforestry.
Exam technique: the difference between mixed cropping and intercropping is the pattern. If the crops are in definite rows, it is intercropping.
Distinguish between nomadic pastoralism and ranching.
Solution: Nomadic pastoralists move their herds from place to place in search of pasture and water, usually on unfenced land. A rancher keeps animals commercially on a large, fenced, fixed area divided into paddocks, with controlled grazing and disease control.
Give two reasons why shifting cultivation is not practised in Rwanda today.
Solution: Any two: land is too scarce for the population, so there is none to leave fallow for years; clearing and burning would destroy forests; bare burnt slopes would erode badly on steep hills.
State two advantages of intercropping coffee with bananas.
Solution: Any two: the farmer gets food (bananas) as well as a cash crop; bananas shade the coffee; banana leaves give mulch; if one crop fails or its price falls, the other still gives income.
Under shifting cultivation, each plot is cropped for 3 years and rested for 9 years. How many hectares does a family need to crop 2 ha every year?
Solution: Cycle = 3 + 9 = 12 years; each plot is cropped for 3 of the 12 years, so the land needed is 12 ÷ 3 = 4 times the area cropped. 4 × 2 ha = 8 ha.
Explain one way agroforestry reduces soil erosion on terraces.
Solution: Tree and shrub roots bind the soil of the terrace edges, and their leaf fall covers the soil, so rain and runoff remove less soil.
Summary
Sources and credits
This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.
