Soil--Lithosphere
Mrs. B-Z
Soil--definition

Complex mixture of eroded rock,
mineral nutrients, decaying organic
matter, water, air, and billions of
living organisms
Indirect resources from
soil

Provides us with wood, paper,
fiber, and medicines
Direct benefits of soil
Purifies water
 Decomposes biodegradable waste

We Study Soil Because It’s A(n)
Medium of crop
production
Great integrator
Producer and
absorber of
gases (CO2
and others)
Waste decomposer
Medium for
plant growth
Source material for
construction,
medicine, art, etc.
Medium of heat and
water storage
Home to organisms
(plants, animals and
others)
Snapshot of
geologic, climatic,
biological, and
human history
Essential natural resource
Filter of water
and wastes
Hydrologic Cycle and the Soil
Soil Properties that are part of the hydrologic cycle.
Moisture
Color
Temperature
Structure
pH
Texture
Horizon
Depths
Bulk Density
Soil Forming Factors
Biota
Parent Material
Topography
Climate
(The first four factors over) Time
These five factors work together to create a unique soil profile made of layers called horizons.
Soil Characterization
Ways to Describe soil:
•Zones or Layers of Soil
•Material contained in Soil
•Soil Texture
•Soil Structure
•Soil Color
•Soil Permeability
•Soil pH
Soil horizons
Zones of mature soil
 layers

Finding and
DescribingSoilHorizons
Pit Technique
First, obtain permission to dig a pit. Obey any and all
safety precautions requested, and ask about power
and water lines.
Forest soil in Florida, USA
Arid climate soil in
New Mexico, USA
Soil profile

Cross sectional view of the
horizons
Soil Profile Comparison
Forest soil in Florida, USA
Forest soil in Tallinn, Estonia
Soil profiles in different geographic regions will be similar if the five soil
forming factors act on those soils in the same way.
Humus
Partially decomposed matter found
in top soil
 Organic layer

A horizon
Top-most layer
 Top soil

B-horizon
Subsoil
 Soil’s inorganic material broken
down
 Clay, sand, silt, and gravel

C horizon
Parent material
 Usually bedrock or some type of
rock

Soil texture

Determined by different sizes and
types of minerals
Horizon
Properties
Soil Texture (continued)
To Determine Soil Texture
loams

Soils with roughly equal amount of
clay, sand, silt, and humus
Horizon
Properties
Soil Texture (continued)
To Determine Soil Texture
Soil structure

How particles are organized and
clumped together
Horizon
Properties
Granular
Soil Structure
With Structure
Block
y
Columna
r
Prismati
c
Platy
Horizon
Properties
Soil Structure (continued)
Without Structure
Single Grained
See hands
for relative
size
Massive
Pencil is
19 cm
Soil porosity

Measure of the volume of pores or
spaces per volume of soil and
average difference between spaces
Soil permeability

Average size of spaces or pores
Horizon Properties
Soil Color
Munsell Notation
Hue
Value
Chroma
Horizon Properties
Soil Color (continued)
1
3
2
4
Horizon
PropertiesSoil Consistence
Loose*
Friable
* Soils with “single grained” structure always have loose consistence.
Firm
Extremely Firm
Horizon
Properties
Soil Texture
Relative Size Comparison of Soil Particles
barrel
plate
coin
Silt
(feels floury)
Sand
(feels gritty)
(2.00 - 0.05 mm, USDA)
(2.00 - 0.02 mm, ISSS)
(0.05 - 0.002 mm, USDA)
(0.02 - 0.002 mm, ISSS)
Clay
(feels sticky)
(< 0.002 mm, USDA)
(< 0.002 mm, ISSS)
Horizon
Properties
Test For Free Carbonates
This is strong effervescence.
Infiltration

Downward movement of water
through soil
leaching

Water dissolves materials in the
upper layers and the solution is
carried to the lower areas
pH

Acidity or alkalinity in water
solutions
Environmental Problems with Soil
Soil Erosion
Famine/Hunger
Soil erosion
Movement of soil components
especially surface litter and top soil
 Caused by

Water
 Wind
 How much soil is there?
http://soil.gsfc.nasa.gov/app_soil/hm
soil.htm

Problems with erosion
Feed millions more people with
billions metric TONS less of top soil
each year
 75 billion metric tons of soil erodes
every year
 How long does it take for one inch
of top soil to form?
 http://soil.gsfc.nasa.gov/inch/soilti
me.htm

Soil Conservation
Reducing erosion
 Restoring fertility

Conservation-tillage
farming
Disturbing the soil as little as
possible when planting
 This holds in more moisture as
well.

Contour Farming

Planting crops in rows according to
the contour of the land
Strip Cropping

Alternating a crop that needs to be in
rows (like corn) with one that does not
(like grass).
Windbreaks

Long rows of trees are planted to
partially block the wind from eroding
the soil
Alley Cropping

Several crops are planted in strips or
alleys between trees or shrubs (wind
breaks).
Restoring
Fertility
Organic Fertilizer—from
plant and animal
materials
 Commercial Fertilizer—
produced from minerals

Crop Rotation

Corn, tobacco, and cotton deplete
soil nutrients so farmers rotate
these from growing in the same
plot of land two seasons in a row.
The next season a legume will be
planted instead like barley, rye, or
soybeans.
How is
food
produced

Industrial Agriculture—
uses large amounts of
fossil fuels, water,
commercial fertilizers and
pesticides
How is food produced

Plantations—industrialized in
tropical, developing countries
(coffee & bananas)
How is food
produced
Traditional—
enough for
yourself and
your
dependents
 More human
labor

Green Vegetation

More energy is given off than was
used to produce it
Livestock

Three units of energy put into
every unit of energy produced.
World
Food


Undernutrition—
enough food to
survive but not
the right food
groups
Malnutrition—
not enough
food to survive
World Food
From 1950-90, food
production rose 3x and
per capita rose 36%.
 88 Developing
countries are behind
with food for
population. But this fell
from 36% to 14%.

World Food

It is surprising to note that there
really is enough food to feed
everyone, but it is not equally
distributed.
Protecting Food

Pesticides—chemicals used to kill
organisms that are undesirable
Pesticides
Insecticides
 Herbicides
 Fungicides
 Nematocides
 Rodenticides

Which uses more pesticides—
a lawn or a farm?

Surprisingly a LAWN—A lot more!
Argument for Pesticides
Saves human lives (malaria and
bubonic)
 Increases food supply
 Lowers cost
 55% of food supply is lost
 37% of US food is lost
 Work faster and better than
alternatives
 Risks are outweighed by benefits

Against pesticides
Genetic resistance
 Broad spectrum could hurt
unharmful organisms
 Wiping out natural predators
unleashing new pests previously
held in check
 Harm wildlife
 Harm humans

Alternatives to Pesticides
Crop rotation
 Plant crops to draw pests to them
 Genetic modification
 Biological predators
 Biological pesticides
 Radiating food

Integrating Pest
Management
See pests as part of the ecosystem
 Find harmony between crops and
pests

Sustainable Agriculture
Combine traditional polyculture and
modern monoculture
 More perennial crops
 Minimize soil erosion
 Reduce deforestation
 Reduce water waste
 Reduce overuse of fossil fuels
 Use organic fertilizers
 Use biological pesticides
