Soil can be conserved by keeping it covered, reducing disturbance, slowing water runoff, limiting wind exposure and replacing nutrients. Techniques include terracing, contour ploughing, cover crops, windbreaks, crop rotation, mulching and controlled grazing.
Level: SL and HL
Subtopic: 5.2 Agriculture and food
Soil conservation maintains soil fertility and reduces erosion, the removal of topsoil by water or wind. This protects the soil system's nutrient and organic-matter storages and supports long-term agricultural productivity.
| Technique | Conservation mechanism |
|---|---|
| Terracing | Converts steep slopes into level steps, slowing surface runoff and increasing infiltration. |
| Contour ploughing | Ploughs across a slope rather than downhill, creating ridges that obstruct runoff and trap soil. |
| Cover crops and mulching | Keep soil covered, reducing raindrop impact, wind erosion and evaporation. Plant roots also bind soil particles. |
| Crop rotation | Alternates crops with different nutrient demands; legumes may improve soil nitrogen and reduce dependence on synthetic fertilizers. |
| Windbreaks | Rows of trees or shrubs reduce wind speed and trap wind-blown soil. |
| Reduced tillage | Limits soil disturbance, preserving soil structure, organic matter and soil organisms. |
| Agroforestry | Integrates trees with crops or livestock; roots stabilize soil while leaf litter adds organic matter. |
| Controlled grazing | Restricts livestock density or rotates grazing areas, preventing overgrazing and allowing vegetation to recover. |
A named example is China's Loess Plateau, where terracing, revegetation and restrictions on grazing reduced severe erosion and improved agricultural productivity. However, conservation policies can affect farmers' access to land and livelihoods, so their social and economic impacts must be considered alongside environmental benefits.
A common misconception is that applying more fertilizer conserves soil. Fertilizer may replace nutrients, but it does not necessarily prevent erosion and can cause eutrophication through runoff.
Exam technique: For an “explain” question, name each technique and link it to a mechanism, such as reduced runoff or increased vegetation cover. For “evaluate,” balance environmental effectiveness against cost, practicality, food production and environmental justice, then reach a supported conclusion using a named example.