1. From Bedrock to Soil

2. What is soil?
Soil is a loose mixture of small mineral fragments, organic material, water, and air that can support the growth of vegetation.

3. All soil is different
Soil (weathered rock fragments) can be made of many different types of rock. The type of rock that the soil was made from is called parent rock.

4. Bedrock Bedrock is the layer of rock beneath the soil.
Some soil is made from bedrock, so it remains above the parent rock.

5. Soil Horizons
Soil is usually layered with humus-rich soil on top, sediment below that, and bedrock on bottom.

6. Humus
Humus is the dark, organic material in soil that is formed from decayed remains of plants and animals.

7. Air & Water
Air must be present in soil to allow water to flow and roots to grow.
Water is essential in dissolving the minerals present in the rock material and distributing it to plant roots.

8. leaching
Leaching is the removal of nutrients that can be dissolved from rock or layers of soil due to the passing of water.

9. Properties of Soil Soil texture Soil structure Soil moisture Aeration
Soil fertility

10. Soil texture
Soil texture is defined as the quality that is based on the proportions, or size, of the particles. What is its consistency?
Soil texture can influence infiltration of water

11. Soil structure
Soil structure is defined as the arrangement of soil particles. (not always spread out evenly)
Can determine infiltration
Sand, less than 2mm in size
Silt, less than .05mm, but more than .002mm
Clay, less than .002mm in size

12. Soil fertility
Soil fertility is the ability for soil to hold nutrients and to supply nutrients to a plant.
Which looks like it had the fertile soil?

13. Fertility can be determined by
Soil color
Soil temperature
Soil moisture
Humus content

14. Soil color
Dark brown or back: contain high levels of humus, very fertile
Reddish or Yellowish: contain oxidized iron, also fertile
Whitish: usually contain salt, unsuitable for farming

15. Soil Temperature & moisture
Plant growth is slowed if soil temperature is too high or too low.
The water that is held in the spaces between soil particles is soil moisture
Amount of moisture in soil determines if water to infiltration or cause run-off

16. Soil Types and Climate

17. Desert Climates
Less than 25cm precipitation per year, so leaching not a problem
Low rate of chemical weathering means slow soil formation & no mineral distribution
Less ability to support plants or animals
High concentration of salt from evaporation

18. Tropical Rainforest Climate
Air is very humid and land received large amounts of water
Temperatures are warm year round allowing rapid decomposition, forming rich humus
Topsoil is thin, and nutrient poor due to leaching and high demand for nutrients from lush plant life

19. Temperate Forest & Grassland climates
Right balance of moisture and temperature
Changes in temperature results in frost action
Thick, very fertile soil develops
Very productive for farming

20. Arctic Climates Like cold deserts
Extreme low temperature, low precipitation
Little plant or animal life
Low decomposition rate, limits humus
Little chemical weathering, so slow soil formation

21. So…. What is the source of soil, and how do they differ?
How do climates affect soil formation?

22. Soil Destruction

23. Erosion
Erosion is the process by which wind, water, gravity, or ice transport soil and sediment from one location to another.
Soil unprotected by plant growth can be lost.

24. salinization
The accumulation of salts in soil is know as salinization.
Common to parts of the world where rainfall is low.

25. Deforestation
Clearing of trees from and area without replacing them is deforestation.
Leaves soil exposed to erosion.

26. Land Degradation
When soil is overused it loses its nutrients it is called land degradation.
This can happen from poor farming techniques, over mining, cutting trees or overgrazing.

27. Desertification
Desertification is a process where land becomes more desert-like as a result of change in climate, prolonged drought, or human activity.

28. Soil Conservation
Soil Conservation is a method to maintain the fertility of soil by preventing erosion and the loss of nutrients.

29. Soil Conservation
There are many ways that farmers help prevent erosion. We will focus on the physical measures.
Contour plowing
Terracing
No-till farming
Cover crops
Crop rotation

30. Contour Plowing
Plowing across the slope of hills to prevent erosion.

31. Terracing
Changing one steep field into a series of small, flat fields.

32. No-till farming
No-till farming is a method of farming where the farmer harvests his crops without turning over the soil.

33. Cover crops
Cover crops are crops that are planted between harvests to replace certain nutrients in the soil and prevent erosion.

34. Crop rotation
Rotating crops from one year to the next in order to slow down nutrient depletion. And reduce insect damage to crops.

35. So…
How does soil quality affect us?
How can we show good stewardship?