“The soil is the great connector of lives, the source and destination of all…
without proper care for it we can have no life.”
- Wendell Barry
1
 During the early exploration of the Great Plains in the
United States, the land was found to be unsuitable for
European-style agriculture.
 The area was called the “Great American Desert.”
2
 The area of the United States from the eastern Rockies
through Nebraska is considered shortgrass prairie.
 Precipitation is lower than the tallgrass prairie to the east,
leading to overall shorter plant species.
3
 Farmers encouraged to settle into these arid shortgrass
prairies had a difficult time farming the soil.
 Cast iron plows
would become
stuck and caked
with clay stuck in
the thick mat of
prairie grasses.
4
 A blacksmith named
John Deere invented a
polished steel plow that
was able to cut through
the Midwestern soil.
 Further improvements,
including gasoline
tractors and combine
harvesters, lead to the
conversion of arid
grassland into fields of
corn, wheat, and cotton.
 Predators like wolves and
coyotes were overhunted
and removed from the
ecosystem.
5
 An unusually wet 10-15
year time period lead to a
series of incredibly
successful harvests.
 Many homesteaders were
convinced by a theory
called “Rain Follows the
Plow” which believed that
this wet period was
actually the result of
increased farming .
6
 About two-thirds of human food consumption is
comprised of just three staple crops – wheat, corn, and
rice.
Rank
Commodity
Production (Metric
Tons)
1.
Sugar cane
1.8 billion
2.
Maize
885 million
3.
Rice
722 million
4.
Wheat
701 million
5.
Milk (cow)
614 million
6.
Potatoes
373 million
7.
Sugar Beet
273 million
Source: http://faostat.fao.org/site/339/default.aspx
7
 Most of the major world food staples are plants.
 Why? In an ecological pyramid,
only about 10% of the
energy in one trophic
level will be incorporated
into the next.
 Consuming plants
directly is more efficient
than raising animals.
 7-12 pounds of grain is
required to produce
a single pound of beef.
8
 In the plains, the primary crop was hard red winter
wheat, a producer that was planted in the fall, lay
dormant over the winter, then harvested in early
summer.
9
 As the formerly untouched soils of the shortgrass
prairies in the Midwest were cultivated, native plants
were replaced by domesticated ones.
 The most
common
plant was
buffalo
grass,
with a 7-8
foot root
depth.
10
 Millions of acres of virgin prairie, about the equivalent of
twice the size of New Jersey, was plowed under.
 For a while, farming was ideal. Precipitation was
unusually plentiful, and the soil was deep and rich.
11
 Soil is a mixture of minerals
and partially decomposed
organic matter.
 Soil begins as rock, but is
gradually broken down
through erosion.
 Mechanical erosion is the
physically breaking down
of rock by wind and water.
 Chemical erosion changes
the molecular structure
12
 Forest soil has an O horizon, which
is mostly non-decomposed plant
litter.
 Grasslands have a much deeper A
horizon, which contains a lot of
organic matter mixed with some
minerals.
 Also called topsoil.
 Both grasslands and forests have a
layer of clay, mostly made of
minerals with little organic matter.
This is the B horizon.
 The last layer in both ecosystems is
parent material, which is the
bedrock from which the soil was
formed.
13
 Following the stock market crash in 1929, wheat prices fell
sharply.
 Farmers tried to recover their losses by overplanting and
increasing crop yields.
 In 1931, a record crop of wheat was harvested. Prices
continued to fall.
 In the winter of 1931-1932, a drought began that would persist
for as long as 7 years in some areas.
14
 The plains of Oklahoma, Texas, Colorado, and New
Mexico experienced 14 dust storms so severe that
visibility was cut to less than ¼ mile.
 The following year, 1933, had 38 severe dust storms.
15
 Mechanical erosion from rainfall takes four forms,
ranked by severity.
 Splash erosion is a tiny crater caused by the impact of a
single drop of water.
 Sheet erosion is the transportation of loose soil
particles along a flow
of runoff water.
 Rill erosion occurs
when the flowing
water coalesces into
small channels.
16
 Gully erosion is the
most severe, caused by
rapidly flowing water
creating deep channels
in the ground.
17
 In arid regions, wind is
the major cause of
erosion.
 One of the worst storms
of the Dust Bowl
dumped 12 million
pounds of eroded topsoil
on Chicago.
Topsoil protected from wind erosion by
native bluestem grass, New Mexico, 1957.
The Dust Bowl, Episode 1: The Great Plow Up.
Dir. Ken Burns. PBS Distribution, 2012. DVD.
19
 Multiple soil conservation techniques were part of the
New Deal programs implemented by President Franklin
Delano Roosevelt.
 Contour plowing reduces water erosion by planting crops
along the slope of the land rather that straight up and
down.
20
21
 Many important commercial plants are row crops,
meaning they must be grown in spaced rows.
 Strip cropping alternates row crops like corn and cotton
with cover crops like oats that completely cover the soil.
 The cover crops trap any soil that erodes from the row
crops.
22
 Terracing converts steeply sloped land into a series of
flattened terraces.
 The stair-like terracing slows the downward runoff of
water, reducing erosion.
23
 Rows of trees can serve as
windbreaks, reducing
erosion by wind.
 In response to the Dust
Bowl, the Great Plains
Shelterbelt was built from
1935-1942.
 220 million trees.
24
 The problems of the Dust Bowl were made even worse by
an invasion of jackrabbits, whose population had
exploded as a result of the removal of their predators:
wolves and coyotes.
25
The Dust Bowl, Episode 1: The Great Plow Up.
Dir. Ken Burns. PBS Distribution, 2012. DVD.
26
 The Dust Bowl caused
the largest famine in
United States history,
forcing millions to
abandon their farms
and look for jobs and
homes elsewhere.
 The actual death
toll is unknown.
27
 An average person needs about 1000 kilocalories per day
to survive.
 Calories come from one of three macronutrients.
 Carbohydrates, with a yield of 4kcal/gram, are our primary
energy source.
 Lipids, with a yield of 9kcal/gram, are what we store our
energy as.
 Proteins, with a yield of 4kcal/gram, make up many of our
body structures.
28
 Undernutrition is the result of a diet that does not meet
an individual’s basic energy (calories) requirement.
 Undernourishment
over an entire
population is called
a famine.
 Famines are most
frequently caused
by drought.
Source: Miller Environmental Science, 13th Edition
29
 Humans also need smaller
amounts of micronutrients, such
as vitamins and minerals.
 A person with a diet lacking in
specific micronutrients or
macronutrients is considered to
be malnourished.
 Kwashiorkor is caused by
insufficient protein
consumption, resulting in a fluid
imbalance in the digestive
system.
 The name is derived from the
native language of Ghana,
meaning “the sickness the older
child gets when the next baby is
born” due to a lack of breastmilk.
30
 Anemia is the name of
any condition that
results in a decrease in
the ability of blood to
transport oxygen.
 Often caused by
malnourishment –
lack of iron in the diet.
 A lack of iodine can
result in a goiter; an
enlargement of the
thyroid gland.
Bangladeshi woman with a goiter.
Source: John Paul Kay/Peter Arnold, Inc.
31
 Different diets have evolved in different regions in the
world to reflect the need to meet micro and macronutrient
requirements with the resources available.
32
33
 As the human population grew in the 20th century,
famines were becoming increasingly common, especially
in developing countries.
 India especially, was on the brink of a massive famine in
1961.
34
 In 1968, a book entitled The Population Bomb predicted,
“The battle to feed all of humanity
is over. In the 1970s hundreds of
millions of people will starve to
death in spite of any crash
programs embarked upon now. At
this late date nothing can prevent
a substantial increase in the world
death rate..”
35
 The prediction of a worldwide famine never came true.
 A series of advancements in farming lead to a massive
increase in crop yields, starting in the 1960s.
36
 The Green Revolution marked three major changes in
modern agriculture:
 The movement away from subsistence agriculture, where
farmers produce to support their families, to industrialized
monoculture, where only a few commercially valuable
crops are grown.
 The introduction of
highly-bred or genetically
modified strains of plants.
 Increased irrigation,
fertilization, and
application of herbicides
and pesticides.
IR8, also called “Miracle Rice”,
produced greater yields than any other
strain in the 1960s.
37
 Irrigation, the application of water to soil, accounts for
largest single share of global water use.
 Irrigation systems are compared with efficiency, a
percentage of the amount of water withdrawn that
actually makes it to the roots of target plants.
 Most irrigation systems are inefficient, with only about
40% of the applied water actually reaching the crops.
38
 Furrow irrigation works by delivering large amounts of
water through small, parallel channels that run through
the field.
 40-60% efficient.
39
 Drip irrigation uses porous tubes above or below ground
that gradually deliver water to the roots of individual
plants.
 90-95% efficient
40
 Center-pivot irrigation involves a piece of equipment
that rotates around a single point, creating a circleshaped irrigation field.
 80% efficiency
41
 Large-scale irrigation
became available in the
Great Plains following the
discovery of the Ogallala
Aquifer, a massive
underground reservoir of
water.
42
 Lack of three nutrients can slow
plant growth: nitrogen,
phosphorous, and potassium.
 These nutrients are depleted
during each growing season and
must be replenished.
 Inorganic fertilizer is
synthetically made from mined
minerals.
 Use has grown nine-fold
worldwide since the 1950s.
43
 Organic fertilizers are derived from plant and animal
matter.
 Animal manure is the dung and urine of livestock.
 Compost is organic matter that has been decomposed by
bacteria, fungi, and other microorganisms.
44
 Some famers will minimize the fertilizer they need by
using a technique called crop rotation.
 During one year, a nutrient-depleting crop (corn,
tobacco) will be grown.
 The following year, legumes (beans, peas, lentils) that
form mutualistic relationships with nitrogen-fixing
bacteria are planted.
Nodules of nitrogenfixing bacteria on a
legume root.
45
 Agriculture accounts for about 15% of the total energy
use in the United States.
 This rate has increased as more and more farming has become
mechanized.
John Deere 2510H
Nutrient Applicator
46
 Biological pests are any organisms that damage crops
and reduce yields.
 Examples: Insects, birds, rodents, weeds.
 Pesticides are chemicals that kill or control populations
of these undesirable organisms.
 Insecticides specifically target insect pests.
 Herbicides specifically target weeds, or undesired plants.
47
 First generation pesticides, in use since
the 1600s, are made from natural
chemicals extracted from plants.
 Nicotine sulfate from tobacco leaves.
 Second generation pesticides, first used
in the 1940s, are synthetically-produced
chemicals.
 DDT
 Following the Green Revolution in the
1950s, pesticide use increased move
than 50 times.
48
 One of the consequences of pesticide use is pesticide
residue; chemicals that remain on food once they are
applied.
 Many pesticides are persistent, meaning they remain in
the environment for a long time.
 They can bioaccumulate , forming higher and higher
concentrations in organisms over a long period of
exposure.
49
 The most famous
example of
bioaccumulation
occurred following the
increased application
of DDT to control
mosquitoes and other
insect pests.
 The pesticide began
accumulating in
greater concentrations
in animals in higher
trophic levels.
 In predatory birds, it
was interfering with
the formation of
eggshells.
50
 Pesticide residues can also affect human
health. Certain types of produce, labeled
the “Dirty Dozen”, are more likely to absorb
and retain pesticides.
 Apples
 Strawberries
 Grapes
 Celery
 Peaches
 Spinach
 Sweet Bell Peppers
 Nectarines (Imported)
 Cucumbers
 Potatoes
 Cherry tomatoes
 Hot peppers
51
 Other types of produce, called the “Clean
Fifteen”, have a protective layer that prevents
them from absorbing as much pesticide residue
or are naturally resistant to pests.















Mushrooms
Sweet potatoes
Cantaloupe
Grapefruit
Kiwi
Eggplant
Asparagus
Mangos
Papayas
Sweet peas (frozen)
Cabbage
Avacados
Pineapples
Onions
Sweet corn
52
 Pesticides have gradually become
less effective as insects have
evolved resistance to them.
 Crop losses from insects has
increased from about 7% in the
1940s to about 13% now.
53
 One alternative to the use of chemical pesticides is to
import natural predators.
 The braconoid wasp, for example, will lay its eggs on the
tobacco hornworm caterpillar. Hatched larvae will feed on
the caterpillar, killing it.
54
 Integrated Pest Management is a strategy where
synthetic pesticides are used as a last resort in dealing
with insects and weeds.
 Biological control, such as the use of natural predators, is
the preferred method.
55
 Organic foods, by definition, have been produced
without any synthetic pesticides or fertilizer.
 Organically-derived fertilizer is still used, as are first-
generation pesticides.
56
 Hydroponics is a method of growing plants without the
use of soil.
 Plants are grown with their roots immersed in water
containing all the necessary nutrients for growth.
 Takes place in a
greenhouse, allowing
for a longer growing
season and
decreased need
for pesticides.
57
 Another alternative to pesticides is to implant DNA into
crops from other species that are resistant.
 These are called Genetically Modified Organisms, or
GMOs.
 Two of the most commonly grown crops in the United
States, corn and soy, are now mostly genetically
modified.
58
 BT corn has been genetically modified to produce certain
proteins from a species of bacteria called Bacillus
thuringiensis.
 The proteins are poisonous to the European corn borer
59
 Roundup-Ready corn is resistant to a glyphosate, an
herbicide sold under the brand name Round-Up.
 The herbicide is sprayed on a field, killing undesired
weeds, but leaving the corn.
60
 As a result of the changes of the Green Revolution and
the introduction of genetically modified organisms,
crop yields have increased dramatically.
 In the United States, the biggest crop produced is corn,
with 84 million harvested acres in 2011.
 As a result, corn is used as an ingredient in many types of
processed foods, including animal feed.
 About 70% of the carbon in the body of a typical American
is from corn.
61