1. “Land, then, is not merely soil; it is a fountain of energy
Soil Science
“Land, then, is not merely soil; it is a fountain of energy
flowing through a circuit of soils, plants, and animals.”
- Aldo Leopold, A Sand County Almanac, 1949

2. The Rock Cycle Erode & Weather SEDIMENT Cool & Harden Melt
IGNEOUS
ROCK
SEDIMENTARY
METAMORPHIC
Erode & Weather
SEDIMENT
Cool & Harden
Compaction & Cementation
Melt
Erode & Weather
Heat & Pressure
Erode & Weather
MAGMA
Melt
Heat & Pressure
Melt

3. What is SOIL???? Soil is not DIRT!
The relatively thin surface layer of the Earth’s crust consisting of mineral and organic matter.
Soil is not DIRT!

4. Q: What’s the difference between soil and dirt?
Location,
location, location!
Dirt is found under your nail,
soil is found beneath your feet

5. The 5 Soil-Forming Factors
Formed from parent material (bedrock) that’s slowly broken down through weathering processes.
climate (water, wind, temperature)
biology (macro- and microorganisms, plants)
relief (topography)
parent material (rocks/minerals)
time
Which is the MOST important??
CLIMATE!!!

6. How would you describe soil?
What is Soil?
How would you describe soil?
Color
Texture
Texture

7. Goethite: yellowish brown Ferrihydrite: reddish brown
Why the color?
Hematite:
red
Goethite: yellowish brown
Ferrihydrite: reddish brown
Calcite: off white
Quartz: white
Organic matter: black

8. There are more than 20,000 different soil types in the United States
Soil Color Variation
Did you know ??????
There are more than 20,000 different soil types in the United States 8

9. Soil Composition Mineral matter comes from parent material
Air & Water percents are interchangeable
Humus is organic matter!
Water
(~25%)
Humus
(~5%)
Air
(~25%)
Mineral
(~45%)

10. Soil Composition continued…
Mineral Matter
Provides nutrient minerals for plants
Provides pore space for water & air
Older soils are:
More weathered
Lower in certain
essential nutrient minerals
Humus: black/dark brown organic material remaining after decomposition
Leaf litter, animal dung, & decaying organisms
Increases the soil’s water-holding capacity by acting like a sponge

11. Soil Composition continued…
Porosity
POROSITY =
amt of soil pore spaces
Pore spaces occupy ~50% of a soil’s volume
Filled with varying proportions of soil water and soil air
Soil Air contains the same gases as atmospheric air, but in different proportions.
More CO2 and less O2
(from organism respiration)
Some bacteria need nitrogen (why??)
The CO2 can accelerate weathering
CO2 + H2O  H2CO3
(carbonic acid)

12. Soil Composition continued…
As water infiltrates the soil, it can carry dissolved materials with it.
Leaching: Removal of dissolved materials from the soil by water percolating downward
Illuviation: Deposition of leached material in lower layers
Some substances completely leach out of the soil because they’re so soluble that they migrate right down to the groundwater.

13. Observe this SOIL PROFILE through soil
O: Organic material
(may be absent)
A: Topsoil - Organic material & mineral grains
E: Leached zone
(may be absent)
B: Subsoil – rich in clay, iron, aluminum
C: Weathered bedrock
Soil layers are horizons and assigned letters
R: Bedrock
(parent material) 13

14. Fun Fact: It takes 100 to 600 years to form an inch of topsoil.
Soil Color by Horizon
Fun Fact: It takes 100 to 600 years to form an inch of topsoil.
A horizon: organic coatings
B horizon: Iron coatings
C horizon: little coating

15. Soil Color – Variation by Geography
Red soils:
Southeast US

16. Soil Color – Variation by Geography
Brown/black soils:
Midwest

17. Soil Color – Variation by Geography
White (gypsum) sands:
New Mexico

18. Soil Organisms
Ex: bacteria, fungi, algae, microscopic worms, protozoa, plant roots, insects, earthworms, moles, snakes, groundhogs, etc.
Soil organisms provide several Ecosystem Services (important environmental functions).
maintaining soil fertility
preventing soil erosion
breaking down toxic materials
cleansing water
affecting atmospheric composition

19. Earthworms & Ants: Mycorrhizae Cycle minerals Aerate the soil
Decomposing corpses contribute organic matter
Assist plants in reproduction by burying seeds
Mycorrhizae
Symbiotic relationship between fungi and the roots of vascular plants
Fungus absorbs nutrients from the soil, and provides it for the plant.
Plant produces food (photosynthesis), and provides it for the fungus.

20. Dr. Greg Pillar, Queens College

21. Physical Soil Properties
PHYSICAL properties:
Texture (%sand, silt, clay)
Porosity & Permeability
Ionic Charge

22. Physical Property: Texture
Texture is determined by its % sand, silt, and clay.
Texture determines the type of soil, and the soil’s properties.
Loam: ideal for agricultural soil

23. Q: What did the shy pebble say to the big rock?
Soil Components
Q: What did the shy pebble say to the big rock?
A. Do you think I’ll ever be a little boulder?

24. Fine Texture - Clay

25. Course Texture - Sand

26. The relative portions of sand, silt, and clay-sized particles
Soil Texture
The relative portions of sand, silt, and clay-sized particles
Sand: 2.0 – 0.05 mm
Silt: 0.05 – mm
Clay: < mm

27. Soil Texture Diagram Practice
What type of soil has:
20% clay, 40% silt, 40% sand
40% clay, 10% silt, 50% sand
30% clay, 60% silt, 10% sand
Find the % of each particle at: A B C
(1) Loam
(2) Sandy clay
(3) Silty clay loam A
60%clay, 20%silt, 20%sand
30%clay, 40%silt, 30%sand
10%clay, 30%silt, 60%sand B C

28. Why is Soil Texture Important?
Property
Sand
Silt
Clay
Water holding
Low
Med-high
High
Aeration
Good
Med
Poor
Nutrient supplying
Pollutant Filtering

29. Physical: Porosity & Permeability again… Think it is important??
Definition?
amt of soil pore spaces
Permeability
Definition?
ability of water to percolate through
____ porosity = ____ permeability

30. Physical: Ionic Charge
Soil minerals are often present as ions.
Minerals ions are either positively or negatively charged.
Clay particles have mostly negative charges on their outer surfaces.
Positively charged mineral ions are attracted to the soil particles and are held for plant use.
potassium K+ and magnesium Mg2+
Negatively charged mineral ions are repelled by the soil particles and are washed away from roots.
nitrate NO3-

31. Physical Characteristics (review)
Why would 100% sand be undesirable for plants?
Why would 100% clay be undesirable for plants?
Answer SAND / SILT / CLAY for the following:
A soil with a lot of _____ would have good drainage, but poor nutrient-holding characteristics.
A soil with a lot of _____ would have poor drainage, but good nutrient-holding characteristics.
A soil with a lot of _____ would have low porosity.
A soil with a lot of _____ would have high permeability.

32. Chemical Property: Acidity
Most soil pH is Plants are happiest at 
Plants are affected by soil pH.
(1) The solubility of certain nutrient minerals varies with differences in pH
Low pH = Al & Mn are more soluble, and can be absorbed in toxic amounts.
High pH = some salts are less soluble, and are less available to the plants.
(2) Soil pH affects the leaching of nutrient minerals.
Acidic soil = positively charged ions are less soluble and are unavailable for plants.

33. Soil Conditioners (Lime)
CaCO3 or MgCO3
Soil amendment / conditioner… not a fertilizer!
Important functions:
Corrects soil acidity
Adds important plant nutrients— Ca & Mg
Reduces solubility & toxicity of certain elements in the soil
Al, Mn, Fe
This toxicity could reduce plant growth under acid conditions.
Promotes availability of major plant nutrients.
Zn, Cu, P
Increases bacterial activity & mutualistic relationships.

34. Soil Conditioners (Compost)
Decayed organic matter
Replaces some nutrients
Improves soil structure
The soil becomes more porous, increasing air circulation and the ability of the soil to absorb and hold moisture.
Makes the soil more spongy!

35. Dr. Greg Pillar, Queens College
Why is Soil Important?
Fun Fact: There are more living organisms in a cubic foot of soil then all of China!
Fun Fact: There are more living organisms in a cubic foot of soil then all of China!
Fun Fact: 1 teaspoon of good soil contains more than 1 million bacteria!
Soil supports
life
L. Clarke and Corbis, 2008
Dr. Greg Pillar, Queens College

36. Dr. Greg Pillar, Queens College
Soil stores important nutrients
Phosphorus (P)
Nitrogen (N)
Potassium (K)
Calcium (Ca)
Magnesium (Mg)
Dr. Greg Pillar, Queens College

37. Dr. Greg Pillar, Queens College
Soil Holds Water
Dr. Greg Pillar, Queens College

38. Dr. Greg Pillar, Queens College
Soil provides support for buildings
Dr. Greg Pillar, Queens College

39. Dr. Greg Pillar, Queens College
Soil filters, buffers, detoxifies….
Soil
Dr. Greg Pillar, Queens College

40. Inputs/Outputs Are these Soil Inputs or Soil Outputs?
Mass Movements (landslides, etc)
Precipitation
Parent Material
Leaching
Infiltration
Uptake by Plants
Organic Matter
Energy O I I O I O I I

41. Transfers/Transformations
Recall:
Transfers simply MOVE things…
they reorganize the soil!
Transformations CHANGE things…
they alter the soil’s makeup in some way.
Are these Soil Transfers or Transformations?
Decomposition
Erosion
Deposition
Weathering
Nutrient Cycling
transformation
transfer
transfer
transformation
transformation

42. Soil Pollution Part II 42

43. Soil Pollution
= any physical or chemical change in soil that adversely affects the health of plants and other organisms living in and on it.
Many soil pollutants…
ARE MOBILE!
move into groundwater, surface water, or air
ARE PERSISTENT!
seep into tiny cracks called micropores and adhere to the soil particles
COME FROM FERTILIZERS / PESTICIDES!
CAN ACCUMULATE!
Sustainable Agriculture practices can help…
…more on this later… 43

44. Salinization of Irrigated Soil
Irrigation water soaks through the soil area where the plant roots grow, adding to the existing water.
The additional irrigation water causes the underground water-table to rise, bringing salt to the surface.
When the irrigated area dries & the underground water table recedes, salt is left on the surface soil.
Each time the area is irrigated this salinity process is repeated.
ALL IRRIGATION WATER CONTAINS SOME DISSOLVED SALTS. 44

45. Salinization of Irrigated Soil
This is in Australia – occurred not from irrigation, but from lack of water-loving plants.
Extra water flows through the soil, mixing w/ salt underground, and bringing it to the surface.
Irrigation salinization is basically the same concept, and the ground would look just like this. 45

46. Effects of Salinized Soil on Plants
Normally, the water concentration inside plant cells is lower than that in the soil resulting in a net movement of water into the root cell.
When soil contains a high amount of salt, its relative water concentration can be lower than the water concentration inside cells. This causes water to move out of the roots into the soil, even when the soil is wet. 46 46

47. Soil Remediation
Until recently, the only way to remove soil contaminants was to…
Why is this a bad thing to do??
Impractical, kills all beneficial organisms, creates waste, expensive…
DIG IT UP
& INCINERATE IT! 47

48. Soil Remediation Techniques
Dilution
Add lots of water; leach out pollutants
Vapor extraction
Inject air into soil to remove volatile organic compounds
Bioremediation
Use microorganisms to degrade organic contaminants (oil, sludge)
Phytoremediation
Use plants to absorb contaminants such as salts or heavy metals. 48

49. DILUTION: Pump & Treat / Soil Washing
Water
Extraction well
GROUND LEVEL
Pollutant low sorption potential = not attracted to soil
easily washed away
Pollutant high sorption potential = not easily washed 49 49

50. … But what’s the problem here?
GROUND LEVEL
How can this problem be fixed???
Source Identification and Removal !!!! 50 50

51. Bioremediation (Bioventing) 51 51

52. Activities that Threaten Soil
15.06.b
Overgrazing
Erosion Control
Removing vegetation
Soil contamination
NOTES
Overgrazing: Namibia, southern Africa
Clear cutting: Mount Rainer, Washington
Terracing to prevent erosion: Peru
Soil contamination (salt build up and pesticides): Colorado 52 52

53. Preventing Soil Erosion
Agricultural: 10% of the worlds best agricultural land damaged due to soil erosion and overuse over last 50 years.
contour plowing
no-till agriculture (no plowing)
terracing slopes
crop rotation - fallow 53 53