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1. SOIL PROCESSES Soil characteristics
Factors affecting soils
2. SOIL What is SOIL?
It is the uppermost layer of the land surface that plants use and depends on for nutrients, water and physical support.
3. Cross section through the land surface
4. SOIL - functions SOIL: the uppermost layer of the land surface that plants use and depends on for nutrients, water and physical support
Functions of soil include the ff:
Soils provide vascular plants with a medium for growth
Supplies organisms with most of their nutritional requirements
A habitat for several plants and animals
A storage bank for water
Its nutrients provide foundation of the world's agriculture
Provides physical support for plants -photosynthesis
5. SOIL – composition… 2 Most soils contain four basic components: mineral particles, water, air, and organic matter. Organic matter can be further sub-divided into humus, roots, and living organisms
6. SOIL – Organic matter ->Humus Fungi and bacteria reduce organic matter to a semi-soluble chemical complex called humus
Humus mixes with soil particles and makes the upper layers of the soil become dark.
Humus provides a number of benefits:
increases soil's ability to hold & store moisture.
reduces the leaching of soluble nutrients.
is an important source of carbon and nitrogen required by plants.
improves soil structure for plant growth.
7. SOIL – texture … 1 The texture of a soil refers to the size distribution of the mineral particles composing the soil.
Soil particles are normally grouped into three main classes:
Sand
Silt and…
Clay
8. SIOL – texture …2
9. SOIL textures – content of sand, clay and loam
10. Porosity Refers to voids in soil that control the flow of water
when water moves through a soil it may carry dissolved material or small particles = translocation
when much material is removed from a horizon in this way = leached and can become porous
11. SOIL pH An important chemical property of a soil
Soil pH is generally related to the concentration of free hydrogen ions in the soil matrix.
Large concentration of hydrogen ions - Acidic.
Low concentration of hydrogen ions - Alkaline.
Soil fertility is directly influenced by pH through the solubility of many nutrients.
At a pH lower than 5.5, many nutrients become very soluble and are readily leached from the soil profile.
At high pH, nutrients become insoluble and plants cannot readily extract them. Maximum soil fertility occurs in the range 6.0 to 7.2.
13. pH of soil & common liquids
14. Soil horizons SOIL HORIZONS: Distinctive horizontal layers of a soil that differ in the following:
color
texture
structure
consistence
porosity
15. Soil Profile and Processes
16. Eluviation - material is removed from a Horizon (exit from Horizon A)
Illuviation - material is moved into a lower horizon (B) Soil profile… 2
17. Soil develops due 5 factors Parent material
Relief - topography
Organisms – (bacteria, earth worms)
Climate – temperature and rainfall -> weathering)
Time – (matured and young soils)