Soil and Vegetation

4 Parts of Soil 1. MINERALS Minerals come from a parent material that is usually rock but can be loose materials that have been deposited by a glacier, the wind, or a river. Contain nutrients for plants

4 Parts of Soil 2. BACTERIA and ORGANIC MATERIAL When plants and animals die, they are decomposed by bacteria in the soil. As bacteria break down the material, nutrients are released into the soil. Humus is the organic material broken down by bacteria and is rich in nutrients.

4 Parts of Soil 3. AIR Plants need air at their roots. The higher the humus level, the more air in the soil. Worms, insects, small animals, and decaying materials provide air pockets in the soil.

4 Parts of Soil 4. MOISTURE Water dissolves the nutrients in the soil taken up by plants. Water is necessary in the chemical and physical processes that weather rock and decay organic materials.

SOIL PROFILE Horizons O – Organic material A – Topsoil B – Subsoil Rich in organic material Dark brown in colour Very slow to form B – Subsoil Combined mineral and organic layer Lighter in colour C – Parent Material Mineral materials from which soil is made Usually bedrock or glacial deposits

LOAM – best soil for growing plants because it encourages root growth and holds moisture allowing plants to take up nutrients.

LEACHING – the continual downward movement of water through the soil. As the water moves down, it dissolves the chemical nutrients in the soil and carries them away. This downward movement takes away the important nutrients.

CALCIFICATION Occurs in drier climates. As water in the topsoil evaporates, water from below is drawn up to replace it. (This is called capillary action.) The process brings the nutrients to the top of the soil.

THE END 