Farmers in the same biome often make opposite choices — one grows cereals, the neighbour runs cattle. That is not random. Soil type and climate set the boundaries of what is possible, and the farmer picks from what is left. This page gives you four biome pairs, and you only need one or two of them in real detail.
📘 What you need to know
Agricultural choices are driven mainly by two environmental factors: soil type and climate.
Soil matters through fertility, structure and water-holding capacity; climate matters through temperature and rainfall.
Steppe and prairie — mollisols, deep and fertile: cereal farming where rainfall allows, ranching where it is drier.
Tropical forest — oxisols, weathered and acidic: soya where soil can be fertilised and limed, cattle ranching where it cannot.
Desert — aridisols, dry and low in organic matter: irrigated crops near water, low-intensity ranching elsewhere.
Temperate forest — brown earths, fertile and versatile: mixed arable and pasture farming, often rotated.
The same biome can produce very different farms, which is exactly what the exam question is testing.
The two factors behind every choice
Ask why a farmer grows what they grow and the answer nearly always comes back to the same two things.
Soil properties. How fertile it is, how well structured it is, and how much water it can hold. These decide what will grow without huge inputs.
Local climate. Temperature and rainfall patterns decide the growing season and whether crops need irrigation at all.
Farmers then adopt whatever practice suits those conditions best. Where conditions are marginal for crops, they move towards livestock. Where they can afford to change the conditions — irrigating, liming, fertilising — the range of options widens.
Money matters too. A farmer who can buy irrigation or lime effectively changes the soil and climate limits, which is why wealth shifts the options available.
The four biome pairs
Each pair shares a biome and a soil type. What splits them is usually water availability, or whether the soil can be improved economically.
Steppe and prairie: cereals or ranching
Mollisols are the grassland soils of the North American prairies, the Eurasian steppes and the South American pampas. They are deep, dark, rich in organic matter and good at holding moisture — close to ideal for agriculture.
Where rainfall is enough, farmers grow high-yield cereals such as wheat, maize and barley, because these soils suit them. Where the steppe is drier and irrigation is not practical, ranching takes over: grasses still thrive on mollisols, so the land becomes grazing for cattle and sheep.
Tropical forest: soya or cattle
Oxisols form under tropical rainforest, in places such as the Amazon Basin, the Congo Basin and Southeast Asia. High rainfall and heat cause rapid decomposition and leaching, so the soils end up heavily weathered, acidic and low in natural nutrients.
Soya bean farming is possible, but only where the soil is fertilised and lime is added to raise the pH. Soya is worth that investment because global demand is high — for human food, oil and livestock feed. Where the soil quality does not support crops, cattle ranching is chosen instead, though overuse leads to soil degradation.
Desert: irrigation or ranching
Aridisols are the dry, sandy soils of North Africa, the Middle East and the American Southwest. They are low in organic matter and nutrients, and hard to cultivate without irrigation or soil improvement.
Where water is available — the Nile Delta, parts of California — irrigation allows crops such as alfalfa, cotton and fruit. But this needs careful water management, because irrigating arid land can lead to salinisation. Where there is no water, low-intensity ranching uses sparse desert vegetation, with few animals per hectare to match the limited feed.
Temperate forest: mixed arable or pasture
Brown earths are found across parts of Europe and North America. They are fertile, well drained, balanced in pH and moderate in organic matter, which makes them the most versatile of the four.
That versatility is the point. These soils support mixed arable farming — wheat, oats and vegetables, usually in rotation to keep the soil healthy — and they support pasture for cattle and sheep. Rotating fields between crops and grass helps prevent soil degradation.
If you only learn one pair properly, learn the tropical forest one. It links soil chemistry, deforestation, global trade and land degradation in a single example, so it can answer several different questions.
WORKED EXAMPLE
Explain how soil type influences the agricultural choices made in the tropical forest biome. [4]
Start from the soil, then follow the consequencesOxisols are heavily weathered, acidic and low in nutrients, because high rainfall and temperature cause rapid decomposition and leaching.Crops therefore need lime to correct acidity and fertiliser to supply nutrients, which only makes economic sense for a high-value crop such as soya.Where farmers cannot afford those inputs, the soil cannot support crops, so cattle ranching is chosen instead.Soil chemistry filters the options, and economics decides between what is leftBringing in cost is what turns a good answer into a top one. Soil sets the limit; money decides whether you can push past it.
💡 Exam tip
Learn the soil name for each biome. Mollisols, oxisols, aridisols and brown earths are quick precision marks.
Always give the reason the soil behaves as it does — leaching in the tropics, organic matter in grasslands.
For any pair, the splitting factor is usually water or affordability of inputs. Name it explicitly.
Name one region per biome: prairies, Amazon Basin, Nile Delta, Western Europe.
You do not need all four pairs in detail. Two well-known ones will answer most questions.
Link back to earlier pages — irrigation in arid areas connects straight to salinisation.
⚠️ Common mix-up
Assuming rainforest soils are rich because the forest is lush. The nutrients are in the living biomass, not the soil.
Mixing up mollisols (grassland, fertile) and oxisols (tropical, poor).
Saying deserts cannot be farmed at all. With irrigation they can — the risk is salinisation.
Treating farmers’ choices as free preference. They are constrained by soil, climate and money.
Forgetting that the same biome supports two contrasting systems. That contrast is the point of the question.
Writing only about climate. Soil properties carry at least half the marks.
Up next: Alternatives to Industrial Farming — regeneration, rewilding, permaculture and zero tillage.
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