1. Basic Soils

2. Is it alive?

3. Is it fragile?
Should we consider soil a fragile resource?

13. Soil loss through plowing

14. Soils A medium for plant growth 1,000 years to form 1” of topsoil
Deplete 1” of topsoil in 100 years or less
Soils
Soil provides a medium for plant growth
Soils are typically comprised of a mineral fraction and an organic fraction
The mineral fraction of soil comes from the decomposition of various rock materials (referred to as "Parent Material")

15. Soils Composition
Soil is composed of three “fractions” An organic fraction A mineral fraction A water and gas fraction

16. Soils Composition An organic fraction
organic materials provide a reservoir of plant nutrients
nutrients are continually recycled as organic materials
Living organisms including plant parts, bacteria, fungi, worms, insects, etc.; dead/decomposing organisms

17. Soils Composition The mineral fraction
Sand, silt and clay
Sand and silt – primary minerals
decomposition of various rock materials
referred to as “parent material”
Clays – secondary minerals
dissolved minerals in solution
precipitate out to form clays
crystalline

18. Soils Composition Gasses and water
Ex. Oxygen (O), carbon dioxide (CO2), nitrogen (N), etc.; H2O
Fills in all of the pore spaces between the soil particles
Larger pore spaces tend to contain more gasses
Smaller pore spaces tend to contain more water

19. The Mineral Fraction So what’s a rock? Consolidated mass of minerals
Then what’s a mineral?
Unique, repeatable combination of elements
And what’s an element?
Found on the periodic table, unique combination of protons, neutrons in a nucleus and electrons

20. Soils Composition Rocks can be divided into three categories
Igneous rock
Sedimentary rock
Metamorphic rock

21. Soils Composition Igneous rock – molten, liquid magma or lava
Divided into two sub-categories
Intrusive igneous rock
Extrusive igneous rock

22. Soils Composition Intrusive igneous rock
“magma” cools and hardens slowly within the crust
forms distinct crystals from slow cooling
often referred to as plutonic rock
ex. granite, quartz

23. Soils Composition Extrusive igneous rock
“lava” is extruded out of the Earth’s crust
cools and hardens quickly outside the crust in contact with air or water
forms small to no crystals from rapid cooling
ex. basalt, obsidian

24. Soils Composition Sedimentary rock
formed from layers of deposited sediments – sands, silts or clays
deposited by wind or water
ex. sandstone

25. Soils Composition Metamorphic rock
rock changed from one form to another over time
changed deep in the earth by heat and pressure
ex. marble changed from limestone and slate changed from shale

26. Soils Composition Sand and silt soils Clays “primary” minerals
direct product of erosion
Clays
“secondary” minerals
result of chemical weathering breaking down primary minerals
minerals leached in solution
deposited out as clays

27. Soils Composition Soils are the uppermost layers of tectonic plates
Formed from weathered and eroded rock or “parent materials”

28. Weathering
Chemical action of air and rainwater and the biological action of plants and animals Rock and minerals disintegrate, decompose and synthesize new compounds and clay minerals

29. Erosion
Wearing away of land surfaces by wind, water, ice and rock-on-rock

30. Soils Combination of sand, silt and clay and organic material
Sand  2.0 mm to 0.05 mm in diameter
Silt  0.05 mm to mm in diameter
Clay  less than mm in diameter
Soils
Soils are a combination of sand, silt and clay and organic material
Sand is the largest size particle  0.2 mm to 0.05 mm in diameter
Silt is the intermediate size particle  0.05 mm to mm in diameter
Clay is the smallest particle size  less than mm in diameter

31. Soil Particle Sizes
Soil Particle Sizes

32. Soil Particle Sizes
As the surface area for a given mass (or volume) of particles decrease in size, the total surface area increases geometrically
In other words—in a given volume, there is more surface area on smaller sized particles than larger sized particles
Sand particles are larger than clay particles
So a given volume of clay particles will have more surface area than sand
Soil Particle Sizes
SPECIFIC SURFACE AREA: the surface area for a given mass (or volume) of particles. When particle size decreases, specific area increases geometrically.

33. Soil Particle Sizes Imagine 2 identical pencils One broken in half
Which has the greatest amount of surface area?
Soil Particle Sizes
The large block
The large block has 6 sides and each side is 64 sq cm
Therefore multiply the 6 sides times the area of each side of 64 sq cm = 384 sq cm (the area of the 6 sides)
The small blocks
The small blocks each have six sides and each side is 4 sq cm
Therefore multiply the 6 sides times the area of each side of 4 sq cm = 24 sq cm (the area of the 6 sides)
Next multiply the area for the six sides of the one cube times the total number of cubes 64
Or 24 sq cm x 64 cubes = 1536 sq cm (the area of all 64 cubes)

35. Bulk Density
Refers to weight per a given volume We talk about: "Light" soils having a higher sand content "Heavy" soils having a higher clay content In reality—a given volume of clay weighs more than the same volume of sand

36. Soil Texture Percentages of sand, silt and clay per volume of soil
Loam soils contain a blend of sand, silt and clay
Loam soils make some of the better gardening soils
Soil texture determined by a "settling" test
Soils
Soil texture can be determined by a "settling" test
"Light" soils have a higher sand content
"Heavy" soils have a higher clay content
Loam soils, some of the better gardening soils, are made of a combination of sand, silt and clay

37. Soil Settling Test
100 grams oven dried, cleaned, screened soil into a blender with: 5 ml 8% Calgon® (sodium hexametaphosphate) solution 100 ml water Blend 5 minutes Pour and rinse blender contents completely into 1000 ml graduated cylinder

38. Soil Settling Test
Fill graduated cylinder to 1000 ml with water Cover graduated cylinder with palm of hand, invert several times getting soil into suspension Set cylinder on flat surface Wait 40 sec., insert Bouyoucos hydrometer into solution

39. Soil Settling Test
Take hydrometer reading Repeat three times and average readings Adjust for temperatures Take another reading at 2 hours Preform calculations

40. Soil Settling Test
The Bouyoucos hydrometer measures density of solution After the 40 sec. reading what soil particles remain in solution—sand, silt or clay? Silt and clay What has settled out first? Sand Why? Sand is heaviest—it settles first

41. Soil Settling Test
After the 2 hour reading what soil particles remain in solution—sand, silt or clay? Clay What has settled out? Silt Why? Silt is heavier than clay—it settles next

42. Soil Settling Test
Assuming we started with 100 grams soil The 40 sec. reading indicated 72 grams in solution How many grams have settled out? 100g – 72g = 28g 28g of what? Sand

43. Soil Settling Test
The 2 hour reading indicated 15 grams remaining in solution How much has settled out of solution? 72g – 15g = 57g 57g of what? Silt

44. Soil Settling Test
What is left in solution? 15g clay 100g soil – (28g sand + 57g silt) = 15g clay Why is the clay still in solution? Clay is the lightest—it stays in solution

45. Soil Settling Test
How much sand, silt and clay is there? 28g sand = 28% sand +57g silt = 57% silt +15g clay = 15% clay =100g soil = 100% soil It checks  Refer to soil texture chart to determine soil texture What soil texture do we have?

46. Soil Texture Settling Test
Turn to the soil texture triangle and find the soil texture class.
We have a “silt loam”
Soil Texture Settling Test

47. Ribbon Test “Quick and dirty” test for soil texture
With a handful of moistened soil, attempt to squeeze out a ribbon of soil between your thumb and forefinger
Clay and silt soils feel smooth
Clay “ribbons” can be 2” long
Sandy soils feel gritty
Sandy soils won’t form ribbons
See handouts at end of PowerPoint
The Ribbon Test
The ribbon test is a "quick and dirty" method to determine soil texture
With a handful of moistened soil, attempt to squeeze out a ribbon of soil between your thumb and forefinger
Clay soils feel smooth and slippery and can be formed into ribbons of soil up to 2" long before they break off under their own weight
Sandy soils feel gritty and cannot be formed into ribbons of any length

48. Soil Structure
Soil structure is determined by arrangement of soil particles
Soil aggregates are soil particles (sand, silt and clay) held together by iron oxides, calcium carbonate, clays and/or silica as well as humus
Texture and structure combined help determine soil pore sizes
Texture and structure greatly determine water movement through soils
Soil Structure
Soil structure is determined largely by the arrangement of the soil particles
Texture and structure combined help determine soil pore sizes
Micropores are small spaces between soil particles
Micropores hold water tightly in the space
Micropores retain various nutrients in solution, making them available to plant roots

49. Soil Porosity
Soil pore sizes determine how well water (and air) moves through soil Infiltration – downward movement water of into soils Percolation – downward movement water of through soils

50. Soil Porosity
Sandy soils drain quickly – don’t hold water Sandy soils have mostly large pore spaces Clay soils don’t drain well – hold water Clay soils have mostly small pore spaces

51. Soil Porosity
Micropores Small spaces between soil particles Hold water tightly – inhibits drainage Retain various nutrients in solution, making them available to plant roots Do not aid in circulation of gasses in soil

52. Soil Porosity Macropores Larger spaces between soil particles
Hold water more loosely - essential to good drainage
Do not retain nutrients in solution particularly well
Aids in circulation of gasses in soil
Soil Structure
Macropores are larger spaces between soil particles
Macropores hold water more loosely and therefore are essential to good drainage
Macropores do not retain nutrients in solution particularly well
Soil aggregates are soil particles (sand, silt and clay) are held together by iron oxides, carbonates, clays and/or silica as well as humus

53. Soil Structure
Soil Structure

54. Soil Horizons
Horizon layers and composition are a product of their surroundings
O-Horizon – organic matter
A-Horizon – darkened by organic matter
E-Horizon – materials leached away downward
B-Horizon – accumulates clays, salts and other fine materials
C-Horizon – loose or cohesive materials, rests on bedrock
R-Horizon – bedrock solid rock
Soil Horizons

55. Humus Residue formed after the decomposition of organic matter
Acts to "glue" soil particles together
Provides a source of carbon to soil
Soils with a higher carbon content referred to as an organic soil (between 12% and 20% organic carbon by weight)
Can change soil structure over time
Humus
Humus is a residue formed after the decomposition of organic matter
Humus acts to "glue" soil particles together
Humus provides a source of carbon to soil; with a higher the carbon content, a soil is referred to as an organic soil (between 12% and 20% organic carbon by weight)
Humus can change soil texture OVER TIME

56. Changing Texture Soil texture takes years to affect . . . Why?
Sand, silt or clay must be added to change texture
Large amounts of sand can be added to change texture and increase drainage to clay soils
Not enough makes mortar!
Expensive!
Raises soil level – something must be removed
Changing Structure & Texture
Soil texture takes years to affect
Soil structure can be changed through tillage
Soil texture and structure can also be affected with the addition of LARGE amounts of amendments
Various amendments can be added to soils to enhance the structure
Large amounts of sand can be added to increase drainage

57. Changing Structure
Soil structure can be changed through tillage Tillage can both loosen and compact soils Organic amendments can be added to soils to enhance the structure Provides humus through decomposition Organic materials slow drainage in sandy soils Organic materials increase drainage in clays

58. Changing Structure Peat moss helps water retention
Never add peat moss to heavy clay soils
Peat moss helps to reduce soil pH
Use compost and soil sulfur in clay soils
Addition of salts through fertilizers or irrigation water can eventually inhibit drainage
Changing Structure & Texture
Compost, which provides humus, can either increase or decrease drainage by changing texture over time
Peat moss helps water retention and will help to reduce the pH of soil; never add peat moss to heavy clay soils
Addition of salts through fertilizers or irrigation water can eventually inhibit drainage
Soil texture and structure greatly determine water drainage through soil

59. “Soil Drainage Test”
Good drainage is a determining factor in successful landscapes
Simple drainage test – dig a hole about 1’ deep
Fill the hole with water
Determine time required for hole to drain
1”/hour – adequate drainage
Less than 1”/hour – problems - clay
Faster than 1”/hour – problems - sand
24 hours or more – serious problems
Puddles after irrigation or rain – indicators of problems
“Soil Drainage Test”
Proper soil drainage is another determining factor in the success of newly planted landscapes
A simple drainage test can be performed by digging a hole about 1 foot deep and fill with water
A drainage rate of about 1” per hour indicates adequate drainage
A drainage rate of less than 1” per hour indicates poor drainage and may indicate a high clay content
A drainage rate of much more than an 1” per hour indicates a high sand content
If the hole drains in less than an 30minutes the drainage is adequate
If the hole hasn’t drained in a 24 hour period serious drainage problems may be an issue and measures to correct it should be considered
Puddles of standing water after irrigation or rainfall are also indicators of potential drainage problems

60. Soil Drainage Test
“Soil Drainage Test”

61. Soil Reaction
Soil reaction refers to the relative amount of free hydrogen ions ( H+ ) in the soil/water solution
In other words how acidic or alkaline is the soil solution
Soil reaction is important in that it determines the availability if different nutrients
Also the susceptibility of plants to various plant disease
Soil Reaction
Soil reaction refers to the relative amount of free hydrogen ions ( H+ ) in the soil / water solution  in other words how acidic or alkaline is the soil solution
Soil reaction is important in that it determines the availability if different nutrients; also the susceptibility of plants to various plant diseases

62. pH – Percent Hydrogen
Soil reaction measured by pH on a scale of 1 through 14
pH of 7 represents a neutral soil
Acidic soils — pH 1 to less than 7
Alkaline soils — pH greater than 7 to 14
Soil Reaction
Soil reaction is measured by pH on a scale of 1 through 14
A pH of 7 represents a neutral soil
The pH of acidic soils measure from 1 to less than 7
The pH of an alkaline soil measures from greater than 7 to 14

63. pH Scale
pH Scale

65. pH Scale
pH Scale

66. pH Scale

67. Appendix: Home Soil Settling Test
You can try this one at home

68. Soil Texture Settling Test
Spread soil on a newspaper to dry; remove all rocks, trash, roots, etc.; crush lumps and clods
Finely pulverize the soil
Fill a tall, slender jar (like a quart jar) ¼ full of soil
Add water until the jar is ¾ full.
Add a teaspoon of powdered, non-foaming dishwasher detergent
Soil Texture Settling Test
1. Spread soil on a newspaper to dry. Remove all rocks, trash, roots, etc. Crush lumps and clods.
2. Finely pulverize the soil.
3. Fill a tall, slender jar (like a quart jar) ¼ full of soil.
4. Add water until the jar is ¾ full.
5. Add a teaspoon of powdered, non-foaming dishwasher detergent.

69. Soil Texture Settling Test
Put on a tight fitting lid and shake hard for 10 to 15 minutes. This shaking breaks apart the soil aggregates and separates the soil into individual mineral particles
Set the jar where it will not be disturbed for 2 to 3 days
Soil particles will settle out according to size; after 1 minute, mark on the jar the depth of the sand
Soil Texture Settling Test
6. Put on a tight fitting lid and shake hard for 10 to 15 minutes. This shaking breaks apart the soil aggregates and separates the soil into individual mineral particles.
7. Set the jar where it will not be disturbed for 2 to 3 days.
8. Soil particles will settle out according to size. After 1 minute, mark on the jar the depth of the sand.

70. Soil Texture Settling Test
After 2 hours, mark on the jar the depth of the silt
When the water clears mark on the jar the clay level. This typically takes 1 to 3 days, but with some soils it may take weeks
Measure the thickness of the sand, silt, and clay layers. a. Thickness of sand deposit _____. b. Thickness of silt deposit _____. c. Thickness of clay deposit _____. d. Thickness of total deposit _____.
Soil Texture Settling Test
9. After 2 hours, mark on the jar the depth of the silt
10. When the water clears mark on the jar the clay level. This typically takes 1 to 3 days, but with some soils it may take weeks.
11. Measure the thickness of the sand, silt, and clay layers. a. Thickness of sand deposit _____. b. Thickness of silt deposit _____. c. Thickness of clay deposit _____. d. Thickness of total deposit _____.

71. Soil Texture Settling Test
12. Calculate the percentage of sand, silt, and clay
[clay thickness] ______________ = _____ percent clay [total thickness] [silt thickness] ______________ = _____ percent silt [total thickness] [sand thickness] ______________ = _____ percent sand [total thickness]
Soil Texture Settling Test
12. Calculate the percentage of sand, silt, and clay. [clay thickness] ______________ = _____ percent clay [total thickness] [silt thickness] ______________ = _____ percent silt [total thickness] [sand thickness] ______________ = _____ percent sand [total thickness]
13. Turn to the soil texture triangle and look up the soil texture class.

72. Soil Texture Hand Test

73. Ribbon Test
Ribbon Test