2. Getting the Dirt on Soils
4 Basic Soil Processes
Presented by Name, Position
Member/Fellow of the Soil Science Society of America

3. General Pathway
This slide is indeed complex but illustrates to process by which rock is weathered and ultimately transformed to soil. It should only be used for advanced students – AP Environmental Science. It should also be pointed out that many of the pathways involve microorganisms to mediate the processes. Thus soil is the product of a series of biogeochemical interactions and its formation is not simple.

4. What are the 4 basic processes that occur in the soil?
Soils are Dynamic
What are the 4 basic processes that occur in the soil?
By definition soil is dynamic and responds to its environment. While there are a great number of processes that occur in the soil they can be grouped together as 4 major factors – addition, losses, transformations, and translocations.
NOTE – Ask students to list some of the processes they see in soil or in the environment. You could also have them work in groups to create a list. Once this is done have the students read off the list and write down the specific processes on the board or on a flip charts.
Examples that have been listed:
Leaching
Rain
Erosion
Animals digging
Decomposition
Flooding
Salting (from a student in western US referring to salinization of farm land)
Mixing
Plowing
Dumping – trash
Deposition
Landslides
Leaf accumulation

5. So after the general pathway slide this diagram should seem simple
So after the general pathway slide this diagram should seem simple. Please remember that although we are simplifying the process all the processes are interacting. Soil is constantly changing due to the 4 processes. This means soil is dynamic –in a constant state of change. This diagram may help understand better how the processes affect the soil.
NOTE; If you asked students to list specific process ask them now to think about which of these general processes the specific ones would fit into. Some might fit into more than 1. You can put the 4 Basic Processes on the board as headings and then move the specific processes to the appropriate Basic Process.
From the examples previously:
Additions
Rain
Flooding – flood waters often leave sediment behind
Dumping – trash: although we should not condone this activity it does add materials to the soil
Deposition – any sediment by wind, water, glaciers etc. can be deposited on the surface. Humans can also add soil material (fill) to the soil as well
Leaf accumulation – leaf litter in the fall adds organic mater to the soil
Landslides – once the landslide material comes to rest it has been deposited on top of the existing soil
Losses
Leaching – this is a loss as leaching refers to materials being removed from the soil and into groundwater.
Erosion – this can be from wind, water or ice
Landslides – the materials that moves down slope off the land surface is a loss
Flooding – Although flooding can leave materials behind it can also remove material and move it down stream thus this is a loss
Translocations
Animals digging – animals from ants to moles to woodchucks to gophers dig holes and physically bring materials to the surface.
Mixing – humans disturb soil as do plants and burrowing animals
Plowing – all forms for tillage move soil around. It may non be far but soil below the surface is often brought up to the surface
Salting (from a student in western US referring to salinization of farm land) - salt moves due to evaporations
Transformations
Decomposition – an major transformation where organic matter such as fresh leaves is broken down by organisms into humus
Salting (from a student in western US referring to salinization of farm land) – the salts that move have to be dissolved in water before they can be moved. This is a transformation – solid to dissolved to solid again

6. Additions (+) Material(s) that can be added to the soil Organic
Mineral
Nutrients
Water
Specific processes
Leaf fall (litter)
Rain and Snow (precipitation)
Fertilization
Deposition
Additions are easy to understand. These consist of materials being deposited on the soil from above as well as materials moving in with ground water. Obvious examples are additions of leaf litter as trees shed their leaves, or additions of organic material as plants and plant root die. Also obvious are additions (deposition) of mineral material due to flooding, landslides, and other geologic events. Perhaps not so obvious is the nearly constant additions of atmospheric dust to the soil surface. Some of this dust can travel long distances and is important to the overall fertility of a region. Rainfall or any precipitation is also an addition.

7. Losses (-) Material(s) removed from the soil body Organic Mineral
Nutrients
Water
Specific processes
Leaching
Erosion
Plant Uptake
Evaporation
Evapotranspriation (ET)
Losses are also rather obvious. Erosion is a major form of soil loss. Erosion can be the slow process of dust being blown away or the rapid large scale process of a landslide moving materials off a slope to anything in between. Loss can also occur as nutrients are taken up by plants (immobilization) and then the plant is harvested and removed. Evapotranspiration is the movement and subsequent removal of water by evaporation form the soil directly as well as from plants as they transpire water As minerals and nutrients move through the soil into groundwater or out of the rooting zone of the plants this too is considered a loss.

8. Translocations (↕) Material(s) moved within the soil body Organic
Mineral
Nutrients
Water
Specific processes
Eluviation
Illuviation
Salt and movement of other soluble materials
Water infiltration
Burrowing
Mechanical disturbances
Translocations are similar to losses in that they involve movement of materials. Translocation differs in that the material is not removed from the soil, instead it moves from one location to another. This internal movement is referred to as illuviation and eluviation. Eluviation is the process by which a material is removed from a zone. Illuviation is the process by which material moves into a zone. Thus eluviation is an exiting of material and illuviation is the moving into of material. Salts, gypsum, and carbonates (lime) are examples of minerals that are soluble in water. These can dissolve in the soil water and then move to wherever the water moves. In some case they may be lost to groundwater but in others they may move only short distances in the soil. As the soil water evaporates the dissolved materials (salts etc.) will precipitate (form solids) out of the water. This is common in arid areas where salts are moved and concentrated at the soil surface as water evaporates. Burrowing animals from ants to tortoises dig holes and physically translocate soil throughout the soil profile. Likewise when we dig holes or till the soil we are moving the soil from lower to higher points (and vice versa) in the profile. Clay and organic matter can also be translocated as water physically moves them deeper into the profile as the water percolates downward.

9. Transformations (↔) Material(s) altered within the soil body Organic
Mineral
Nutrients
Water
Specific processes
Decomposition
Freeze-thaw
Compaction
Dissolving solids
Mineral formation
Understanding transformations takes a little more thought. As you consider the dynamic and changing nature of the soil, transformations become obvious. For example the leaf litter that is added is eventually decomposed. This decomposition is a transformation process. Likewise as rocks weather to soil, this too is a transformation process. The initial minerals in the rock are transformed to clays and other minerals in the soils over time. If the soil is compacted the amount of pores or void space is reduced. This too transforms the soil by decreasing gasses' and water’s ability to move through the soil. Compaction also makes it harder for roots to penetrate the soil. When water freezes it is transformed from a liquid to a solid, thus if this occurs in soil it too is a transformation. Also as water freezes it expands. This action can help the particles in the soil aggregate thus forming soil structure.

10. Examples
The next few slides give examples of different processes. Ask the students if they can name the basic as well as the specific process.

11. Transformation –
Freeze thaw. Ice crystals in soil. The water is transformed and the soil will begin to aggregate due to the pressure of the ice.

12. Dust Bowl Photo from internet – location unknown – replace as needed
Loss
Erosion during the dust bowl of the 1930’s. Although the soil in the air is a loss when is settles back to the ground – that is deposited – it becomes an addition to the soil it landed upon.

13. Transformation and subsequent Translocation or Loss of the dissolved materials
Solution of hornblende – Scanning electron micrograph about 0.1mm across

14. Crayfish burrow in a soil in Ohio.
Translocation
Burrowing crayfish move soil to surface to create their burrows. Subsequently the topsoil can infill the burrows once the crayfish abandons it. The result is the vertical dark streaks.
The scale in in cm.

15. Photo from Scoop I think
Dust in atmosphere off the wet coast of Africa
Loss from the Sahara but once the dust settles (deposited) it is an Addition
Erosion – wind action in Sahara

16. Ground squirrel tunnels that were under snow during the winter
Ground squirrel tunnels that were under snow during the winter. As the squirrels moved and excavated into the soil the some of the tunnels are filled with soil from deeper in the profile.
Translocation
Burrowing or animal activity

17. The leaf litter of Coniferous vegetation is often highly acid so extreme eluviation due to the formation of organic acids from the litter is common in the soil. The resulting soil often has a thick eluviated or bleached zone with an accumulation of humic material or Fe and Al oxides a depth.
Translocation
The bleached zone represent eluviation. The dark zone below it represents illuviation

18. SSC 361
4/17/2017
Application of liquid animal waste as a fertilizer.
Addition
Fertilization

19. Addition
Irrigation

20. White material is salt. Location is semiarid in CA.
Salt accumaulate s at surface due to evaporation of salt enrich soil water.
Translocation to bring salt to surface – Transformation to first dissolve and then precipitate the solid back to a solid
Salt movement and dissolving.

21. Leaf fall in Fall
Additions (leaf litter fall) and eventually Transformation (decomposition of leaves) and Translocation (moving organic mater into the soil)

22. Snow
Addition (precipitation – rain or snow)

23. Questions?

24. The UN Declared 2015 as the International Year of Soils (IYS) to bring more attention to this important natural resource. The Soil Science Society of America celebrates IYS and is happy to bring you this presentation. We hope you take the time to learn more about soils at the many resources listed at the end of this presentation, as you learn more about how…
Soils Sustain Life

25. Thank you for listening! For further information, visit:
Soils.org/discover-soils – information about all things soil!
Soils4teachers.org – Lesson plans, activities, etc. for teachers
Soils4kids.org – activities for the K-12 audience
Follow us on facebook.com/iheartsoil
Soils sustain life!