Transfers move matter from one location to another without changing its chemical nature, whereas transformations change matter chemically, physically, or biologically. In IB ESS subtopic 5.1 Soil, both processes connect soil storages and help determine soil fertility and productivity.
How the processes work
Soil is an open system containing storages of minerals, dead organic matter, water, air, and living organisms. Matter enters, moves between horizons, changes form, and may eventually leave the system.
| Process type | Soil examples | What happens |
|---|---|---|
| Transfer | Infiltration and percolation | Water enters the soil and moves downward through pore spaces. |
| Transfer | Leaching | Dissolved mineral ions are carried from upper to lower horizons or out of the soil. |
| Transfer | Biological uptake | Plant roots move water and mineral nutrients from soil into biomass. |
| Transfer | Bioturbation | Earthworms and other organisms redistribute soil particles and organic matter. |
| Transformation | Decomposition | Decomposers break dead organic matter into simpler substances. |
| Transformation | Humification | Partly decomposed organic material is converted into humus. |
| Transformation | Mineralization | Organic nutrients are converted into inorganic forms available for plant uptake. |
| Transformation | Weathering | Parent material is physically or chemically broken down, contributing mineral particles to soil. |
A common misconception is that leaching is a transformation. It is a transfer because dissolved substances change location; their chemical identity does not necessarily change.
In the Amazon Basin, rapid decomposition transforms dead organic matter and releases nutrients, while plant uptake quickly transfers those nutrients into biomass. After forest clearance, reduced uptake and intense rainfall can increase leaching, lowering soil fertility. This shows how land-management decisions alter soil processes and affect the long-term sustainability of farming communities.
Exam technique
For an IB distinguish question, address both terms throughout: state that transfers change location, while transformations change form. For an explain question, identify a process, describe its mechanism, and connect it to a consequence such as nutrient availability, productivity, or soil degradation. In a systems diagram, represent storages with boxes and transfers or transformations with clearly labelled arrows.