Soil conservation methods
Big idea: Soil conservation aims to prevent erosion, maintain fertility, and protect this vital resource. Prevention is essential because soil takes centuries to form but can be destroyed in years.
Methods to prevent erosion
- Contour ploughing — plough across slopes, not up/down, to slow water runoff
- Terracing — create flat steps on hillsides (like rice paddies)
- Windbreaks / shelterbelts — trees reduce wind erosion
- Cover crops — plants grown between seasons to protect bare soil
- Mulching — organic matter on surface protects from rain impact
- No-till farming — avoid ploughing, leave residues on surface
Methods to maintain fertility
- Crop rotation — alternate crops to prevent nutrient depletion, break pest cycles
- Intercropping — grow multiple crops together (e.g., maize with beans)
- Green manures — crops ploughed back into soil to add organic matter
- Composting — add decomposed organic matter to build humus
- Nitrogen fixation — grow legumes to add nitrogen naturally
- Integrated nutrient management — combine organic and mineral fertilizers
Methods to restore degraded soil
- Adding organic matter — compost, manure, biochar
- Liming — raise pH of acidic soils
- Gypsum application — improve structure of sodic soils
- Reforestation — trees stabilize soil, add organic matter
- Resting land — fallow periods allow recovery
EXAM ESSENTIAL: Be able to explain HOW each method works, not just name it. Example: "Crop rotation prevents nutrient depletion because different crops have different nutrient requirements, AND it breaks pest cycles because pests specific to one crop cannot build up."
IB-style question — soil conservation on a slope
A farmer on a sloping hillside loses topsoil after heavy rain. Describe two soil conservation methods they could use to reduce erosion. [4]
How the marks are earned
- Method 1 — terracing
• cut level steps into the slope
• shortens slope length → slows runoff → less topsoil washed away - Method 2 — contour ploughing / cover crops
• plough across the slope or keep roots in soil year-round
• binds soil and traps water → less runoff
Final answer
Each method needs HOW it works — a name without a mechanism earns only 1 of the 2 marks.
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