5.1.9—Soil foundation role
- Syllabus
- First assessment 2026
- Objective
- 5.1.9
- Level
- SL
Separate What Soil Gives a Plant from Where Carbon Comes
Soil provides anchorage, water storage, nutrients and a seed environment; atmospheric CO₂ supplies most plant carbon.
N, P and K support different functions, but fertilizer cannot replace light, water, roots or carbon fixation. Trace the resource to its source and process.
A seed bank and moist soil support germination, while leaves take CO₂ from air and photosynthesize biomass.
Fertilizer supplies selected mineral nutrients; most plant carbon enters as atmospheric CO2 fixed during photosynthesis, not from soil fertilizer.
Plant nutrition is not one soil input; distinguish water, minerals, anchorage and carbon.