“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

Plant Agriculture

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.”

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The Great American Desert

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.

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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 inthe thick mat ofprairie grasses.

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Farming in the Prairie

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.

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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 .

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About two-thirds of human food consumption is comprised of just three staple crops – wheat, corn, and rice.

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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

Staple Crops

Most of the major world food staples are plants.Why? In an ecological pyramid,

only about 10% of theenergy in one trophiclevel will be incorporatedinto the next.Consuming plants

directly is more efficientthan raising animals.

7-12 pounds of grain isrequired to producea single pound of beef.

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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.

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As the formerly untouched soils of the shortgrass prairies in the Midwest were cultivated, native plants were replaced by domesticated ones.

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The most common plant was buffalo grass, with a 7-8 foot root depth.

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.

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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

Soil

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.

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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.

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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.

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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.

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Erosion from Water

Gully erosion is the most severe, caused by rapidly flowing water creating deep channels in the ground.

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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.

Wind Erosion

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.

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Soil Conservation

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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.

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Terracing converts steeply sloped land into a series of flattened terraces.The stair-like terracing slows the downward

runoff of water, reducing erosion.

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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.

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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.

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The Dust Bowl, Episode 1: The Great Plow Up. Dir. Ken Burns. PBS Distribution, 2012. DVD. 26

The Dust Bowl causedthe 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.

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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.

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Human Nutritional Needs

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 mostfrequently causedby drought.

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Famines and Undernutrition

Source: Miller Environmental Science, 13th Edition

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.

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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.

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Bangladeshi woman with a goiter.Source: John Paul Kay/Peter Arnold, Inc.

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Different diets have evolved in different regions in the world to reflect the need to meet micro and macronutrient requirements with the resources available.

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The American School Lunch…

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.

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Population Bomb

In 1968, a book entitled The Population Bomb predicted,

“The battle to feed all of humanityis 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..”

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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.

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The Green Revolution

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.

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IR8, also called “Miracle Rice”, produced greater yields than any other strain in the 1960s.

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.

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Agricultural Water Usage

Furrow irrigation works by delivering large amounts of water through small, parallel channels that run through the field.40-60% efficient.

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Drip irrigation uses porous tubes above or below ground that gradually deliver water to the roots of individual plants. 90-95% efficient

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Center-pivot irrigation involves a piece of equipment that rotates around a single point, creating a circle-shaped irrigation field.80% efficiency

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Large-scale irrigation became available in the Great Plains following the discovery of the Ogallala Aquifer, a massive underground reservoir of water.

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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

Fertilizer

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.

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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.

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Nodules of nitrogen-fixing bacteria on a legume root.

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.

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Energy

John Deere 2510H Nutrient Applicator

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.

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Pest Control

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.

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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.

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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.ApplesStrawberriesGrapesCeleryPeachesSpinachSweet Bell PeppersNectarines (Imported)CucumbersPotatoesCherry tomatoesHot 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.MushroomsSweet potatoesCantaloupeGrapefruitKiwiEggplantAsparagusMangosPapayasSweet peas (frozen)CabbageAvacadosPineapplesOnionsSweet corn

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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.

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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.

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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.

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Integrated Pest Management

Organic foods, by definition, have been produced without any synthetic pesticides or fertilizer.Organically-derived fertilizer is still used, as are

first-generation pesticides.

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Organic Agriculture

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, allowingfor a longer growing season and decreased need for pesticides.

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Hydroponics

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.

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Genetically Modified Organisms

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

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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.

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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.

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Harvest