Sub-topic 5.1 Introduction to soil systems

Soil profile

the layers (horizons) seen in a vertical cut through soil

soil system storages

organic matter, organisms, nutrients, minerals, air and water

transfers in soil

biological mixing, leaching

leaching

minerals dissolved in water moving through soil (down)

Inputs to soil system

leaf litter, inorganic matter from parent material, precipitation, energy

parent material

the rock from which soil forms locally

outputs from soil system

uptake by plants, soil erosion

transformations in soil

decomposition, weathering, nutrient cycling

properties of soil

mineral and nutrient content, drainage, water holding capacity, air spaces, biota, potential to hold organic matter, primary productivity

soil texture triangle

diagram to compare the composition of soil with sand, clay and loam percentages identified

physical weathering

involves the mechanical breakdown of pieces of rock into smaller pieces e.g. frost, salt, insolation and biological weathering,

chemical weathering

breaks down chemical bonds, chemically modifies the rock minerals, and produces new compounds; the most common types are oxidation, carbonation and hydrolysis. Lichens can chemically weather rock.