1. 5.1 - Introduction to Soil Systems - TASK 1

2. Video Introduction
Watch this video introduction into the importance of soil, and the issue of soil degradation.

3. Explain what you understand by this diagram.
Soil interacts with the atmosphere, lithosphere (rock), biosphere (living matter) and hydrosphere (water).
The water cycle moves through the soil and may evaporate from the surface
The atmosphere contains matter that is deposited on the soils
Rocks in the lithosphere weather to form soils
Plans in the biosphere extract nutrients from the soil

4. What is soil?
Explain how soil is made up of the following aspects: rock particles, humus, water air, soil organisms
Rock particle: from underlying rock or from rock particles transported to the environment.
Humus: plant and animal matter in the process of decomposition
Water: seeping down from precipitation or moving up from underground sources by capillary actions
Air: oxygen and nitrogen
Soil organisms: soil invertebrates, microorganisms, large animals

5. HORIZONS Organic Matter: Little layer of plant
Surface Soil: Layer of mineral soil with most organic matter
Subsoil: This layer store up iron, clay aluminium and organic compounds
Parent Rock: Layer of large unbroken rocks.
Bedrock: Layer of partially weathered bedrock.
Organic Matter
Surface soil
Subsoil
Parent Soil
Bedrock =

6. HORIZONS
Materials are sorted and layers are formed by water carrying particles either up or down - known as translocation.
In hot, dry climates, where water evaporates at the soil surface and water from lower soil layers moves upwards. In doing so, it dissolves minerals and takes them to the surface, where the minerals are left behind when the water evaporates. This also happens in irrigation and is called salinization.
In colder and wetter climates, water flows down in the soil, dissolving minerals and transporting them downwards. This is leaching.

7. SOIL TRIANGLES Look at the percentages on the sides of the triangle.
The left numbers represent the percentage of clay, the right represents the percentage of silt and the bottom the numbers represent the percentage of sand
To classify a soil sample, we have to find the intersection of the three lines that correspond the three proportions

8. State which soils are the most desirable for agriculture and why.
Loam Soil
Loam soil has fairly equal portion of sandy soil, silty soil and clay soil
The sand particles: good drainage, good air supply to the roots
The clay retains water and supplies nutrients
The silt particles help to hold the sand and clay particles together.

9. Explain the importance of Soil Porosity and Permeability.
Soil porosity is the amount of space between particles
Contains oxygen and water for plants
Soil Permeability is the ease at which gases and liquids can pass the soil
If soil is not permeable and if water stays on the surface it will affect plant growth.
If soil is too permeable it will wash away fertilizers and other chemical substances.

10. SOIL SUSTAINABILITY Explain why soil is a nonrenewable resource.
Soil is a nonrenewable resource because soil formation takes a very long time. Therefore, once it is lost it cannot be replaced quickly.
Natural soil renewal rate mm per year.

11. Explain the importance of nitrates, phosphates and potassium (NPK) and how they can be replaced in soils.
Nitrate: for leaf and stem
Phosphates: for root system
Potassium: for flower head or fruit
Chemical fertilizer
Growing legumes
Crop rotation
Application of organic matter

12. Using what you have learnt...
Explain why the crop yield on a farm may consistently decrease over a ten year period whether fertilisers are used or not.
(p243 of should help)