Key Idea: Topic 5.1 explains what soil is, how it forms, what controls its properties, how soil affects ecosystem productivity (NPP), and why soil degradation is a major sustainability issue.
๐งฑ Soil formation + composition
Soil is effectively non-renewable on human timescales (forms extremely slowly).
๐งช Soil properties + horizons
๐ฑ Soil + productivity (NPP)
For 5โ7 marks, write cause โ effect chains (e.g., humus โ โ CEC โ โ nutrients held โ โ plant uptake โ โ NPP โ).