IB Environmental systems and societies 5.2F Agricultural Choices and Farming Approaches Notes

Same Biome, Different Choice: Local Soil and Climate Decide What Farmers Grow

1. Within a single biome, soil type, rainfall reliability, and drainage push farmers toward completely different systems.
2. Farmers pick the system that stays productive and economically viable within those local limits.

Steppe and Prairie (Mollisols): Cereals Where Rain Is Reliable, Ranching Where It Is Not

1. Mollisols are deep, fertile soils with high organic matter, so fertility is rarely the limiting factor here.
2. The decision comes down to water: areas with reliable rainfall grow cereals such as wheat, maize, and barley.
3. Where rainfall is low or unpredictable, farmers switch to extensive cattle or sheep ranching, because grasses survive drought that would fail a cereal crop.
4. Mechanisation and global grain markets pull the wetter zones toward intensive cereal monocultures.

Tropical Rainforest (Oxisols): Input-Heavy Soya or Ranching on Cleared Land

1. Oxisols are heavily weathered, acidic, and low in nutrients, so most fertility sits in the living biomass, not the soil.
2. Growing soya here works only with lime, phosphorus, and synthetic fertiliser to correct the soil first.
3. Where inputs are not affordable, farmers choose cattle ranching on newly cleared land.
4. Ranching looks profitable at first but exhausts the soil, which drives further deforestation.

Desert (Aridisols): Irrigated Cropping or Nomadic Ranching, Shadowed by Salinisation

1. Aridisols are dry, low in organic matter, and prone to salt buildup.
2. Where irrigation water reaches the land, such as the Nile Valley or Arizona, farmers grow dates, cotton, and alfalfa.
3. Irrigation carries a cost: evaporation leaves salts behind, causing salinisation that can force land abandonment.
4. Without irrigation, nomadic pastoralism dominates, because hardy animals graze sparse vegetation that no crop could use.

Temperate Forest (Brown Earths): Mixed Arable and Pastoral Farming

1. Brown earths are moderately fertile and well-drained, so they support both crops and pasture.
2. This favours mixed farming, where livestock and crops feed each other's nutrient cycles.
3. Manure, crop residue, and grass leys keep soil healthy through natural nutrient recycling.
4. Crop and pasture rotation raises long-term fertility and lowers pest buildup.

Alternative Farming Approaches: Cutting Inputs by Working With Ecosystems

Soil Regeneration

1. Soil regeneration rebuilds organic matter, microbial life, and nutrient cycling.
2. It relies on mulching, reduced tillage, legume rotation, composting, biochar, and cover cropping.
3. Regenerated soils store more carbon, need less synthetic input, and cope better with drought.