Soils
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Soils
How much soil is there?
Pretend that this apple is the planet Earth, round, beautiful, and full of good things. Notice its skin, hugging and protecting the surface.Water covers approximately 75% of the surface. Right away, cut the apple in quarters.
Toss three quarters (75%) away.
Soils
How much soil is there?
The three quarters (75%) you just removed represents how much of the earth is covered with water - oceans, lakes, rivers, streams. What is left (25%) represents the dry land. 50% of that dry land is desert, polar, or mountainous regions where it is too hot, too cold or too high to be productive. So cut that dry land quarter in
half and toss one piece away.
Soils
How much soil is there?
When 50% is removed, this is what is left. (12.5% of the original) Of that 12.5%, 40% is severely limited by terrain, fertility or excessive rainfall. It is too rocky, steep, shallow, poor or too wet to support food production.
Cut that 40% portion away.
Soils
How much soil is there?
You are left with approximately 10% of the apple.
Peel the skin from the tiny remaining sliver.
Soils
How much soil is there?
The remaining 10% (approximately)- this small fragment of the land area - represents the soil we depend on for the world's food supply. This fragment competes with all other needs - housing, cities, schools, hospitals, shopping centers, land fills, etc., etc. And, sometimes, it doesn't win.
Soils
Soils
A. Define soil: product of nature having both depth and surface area, resulting from both DESTRUCTIVE and SYNTHETIC forces. Weathering & microbial decay of organic matter are examples of DESTRUCTIVE forces, while the formation of NEW minerals & the development of different layers are synthetic forces at work.
Soils
5 tons of topsoil spread over an acre is only as thick as a dime. 5 – 10 tons of animal life can live in an acre of soil. Natural processes can take 500 years to form 1 inch of topsoil.
Soils
1. Physical Weathering Soils: B. Types of Weathering
2. Chemical Weathering
CO2 + H2O = Carbonic Acid This mild acid etches the surface
of rock gradually weathering it away.
Soils: B. Types of Weathering
3. Biological Weathering
Roots
Soils: B. Types of Weathering
3. Biological Weathering
Lichens
Soils: B. Types of Weathering
"The threat of nuclear weapons and man's ability to destroy the environment are really alarming. And yet there are other almost imperceptible changes - I am thinking of the exhaustion of our natural resources, and especially of soil erosion - and these are perhaps more dangerous still, because once we begin to feel their repercussions it will be too late." (p144 of The Dalai Lama's Little Book of Inner Peace: 2002, Element Books, London)
Soils: C. Erosion
1. Water
The rain drop on impact with the soil throws small particles into the air. Flowing water then picks these soil
particles up and carries them away.
Soils: C. Erosion
1. Water
An unprotected crop field severely eroded after a rain storm. Much of the good top soil has washed to the bottom of the field. Other amounts have washed down into an adjacent stream.
Soils: C. Erosion
2. Wind
With wind erosion, dry soil particles are dislodged by other blowing soil particles. The
1930's photo depicts a town soon to be enveloped by a giant dust storm.
Soils: C. Erosion
2. Wind
With wind erosion, dry soil particles are dislodged by other blowing soil particles. The
1930's photo depicts a town soon to be enveloped by a giant dust storm.
Soils: C. Erosion
3. Ice
Large rock being moved by an Alpine glacier. The figure on the right is almost 6 feet tall
Soils: C. Erosion
3. Ice Soils: C. Erosion
3. Ice Soils: C. Erosion
1. Mineral: 44% - 49%
2. Organic: 1% - 6%
3. Soil Water: 25%
4. Soil Air: 25%
Soils: D. Soil Components by Volume
___% pore ___ % solid50 50
Relative Size Comparison of Soil Particles
Soils: E. Classification by Particle Size
Relative Size Comparison of Soil Particles Barrel
Sand (feels gritty)
(2.00 - 0.05 mm, USDA) (2.00 - 0.02 mm, ISSS)
Plate
Silt
(feels floury) (0.05 - 0.002 mm, USDA) (0.02 - 0.002 mm, ISSS)
Coin
Clay
(feels sticky) (< 0.002 mm, USDA) (< 0.002 mm, ISSS)
Soils: E. Classification by Particle Size
Soil Components How Soil Particle Size and Surface Area Affect
water holding capacity.
Soils: E. Classification by Particle Size
Soils: E. Classification by Particle Size
Component H2O Holding Capacity Aeration Fertility
Sand
Silt
Clay
Physical Nature of soil separates.
Low None
Poor High
Low Good None
High
Excellent
Soils: F. Physical Nature of Soil Separates
Soils: G. Soil Texture Define: The percentage of sand, silt and clay that a soil consists of.
H. Define Loam Soil: Approximately equal amounts of sand, silt and clay.
Soils
Soils: I. Soil Solution Define: The liquid phase of soil & the dissolved solutes that are in it.
J. Soil Air: The gaseous phase of soil. The relative mixtures of O2, N2, and CO2
Soils: K. Soil pH 1. Define pH: degree of acidity or alkalinity.
Increased acidity (High H+ concentrations)
Increased alkalinity (Low H+ concentrations)
7.0
Range of pH for soils common in Arid regions (S.W. Deserts)
Range of pH for soils common in Humid regions (typical Midwest & East Coast)
Extreme pH for acid peat soils (as in Peat Bog)
Attained only by alkali mineral soils (Utah Salt Flats, Nevada)
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Soils: K. Soil pH 2. pH Scale
Soils: K. Soil pH 3. Humus
The dark residue remaining after the complete decomposition of organic matter.
Soils: K. Soil pH 4. Why is soil pH so important? a. Soil pH & nutrient uptake
Clay or Humus Particle
(-)
Na+ Mg+
Ca+
Fe+
K+
NH3+
Cations from particles exchange with cations in soil solution.
Ion exchange
Ion exchange Roots pickup
cations from soil solution.
•Nutrient uptake and microbial activity depends on soil pH.
Soils: K. Soil pH 4. pH Scale
b. What is the ideal pH for microbial activity and nutrient availability and uptake?
Soils: K. Soil pH Plant adaptation to acid soil
Soils: II. Soil Problems A. Acid Soils
1. Define: excessive amts. Of hydrogen ions [H+] that interfere with normal plant growth & development.
2. Amendments used to cure acid condition.
Limestone
CaCO3 + H+ CO2 + H2O + Ca++
CaCO3●MgCO3+ H+ CO2 + H2O + Ca+++ Mg++
(Dolomite)
To Raise Soil One Unit of pH
Hydrated Lime Dolomite Ground
Limestone
Light Soil 100 sq. ft
11/2 pounds 2 pounds 2 1/2
pounds Heavy Soil 100 sq. ft.
3 1/2 pounds
5 1/2 pounds 6 pounds
Soils: II. Soil Problems B. Saline soil
2. Sources of salt: a. Evaporation of water. b. Geological deposits of salt.
3. Remedies for saline soils: a. Use higher quality water. b. Deep water (flush). c. Deep plow. d. Grow salt tolerant crops; like alfalfa & cotton.
1. Define: contains excessive amts. of water soluble salts that interfere with normal plant growth & development.
Soils: II. Soil Problems C. Alkali soils
1. Define: Excessive amounts of Na (sodium) that interfere with plant growth and development.
2. Remedies for alkali soil: a. Soil sulfur or b. Gypsum (CaSO4)
Soil sulfur.
To Lower Soil One Unit of pH
Soil Sulfur
Ammonium Sulphate
Iron Sulphate
Light Soil 100 sq. ft
1/2 pounds
2 1/2 pounds
3 pounds
Heavy Soil 100 sq. ft.
2 pounds
6 1/2 pounds
7 1/2 pounds
Soils: II Soil Problems D. Caliche or hardpan
1. Limestone fused with gravel and rock by evaporation of water. 2. Characteristic of soils south of the Mogollon Rim. 3. Impenetrable to roots.
Soils: III. Cryptobiotic Soil A. What is cryptobiotic soil?
1. Means “hidden life”. 2. Crust on the surface of the soil that consists of numerous
microbe species.
Scabby crust common in the Sonoran Desert.
Soils: III. Cryptobiotic Soil B. Importance of cryptobiotic soil.
1. Increases fertility. 2. Slows runoff of rain (increases soil moisture and stabilizes the soil. 3. Protects against erosion. 4. Affects abundance, diversity, and health of plant species.
Soils: III. Cryptobiotic Soil C. How are human’s activities negatively affecting cryptobiotic crusts?
1. People, cattle, and vehicles crush the crust. 2. Squashed crust produces less nitrogen and
carbon.
Soils: III. Cryptobiotic Soil D. How can we manage cryptobiotic soil?
1. Drive only on developed roads & jeep trails. 2. Hike on established trails. 3. Camp in a minimized zone of impact.
Soils: III. Cryptobiotic Soil
Soils: IV. Compost Making A. Compost Pile
Soils: IV. Compost Making B. Worm Composting
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