Chapter 12 Soil and Agriculture

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Essential Questions Covered• What are the components of the soil?• How is soil formed?• What are some of the effects of soil erosion on the

land?• Describe the impact of human activities on the land.• How do recycling and composting programs affect

the soil?• What impact do pesticides have on the soil?• What affect do fertilizers have on the nitrogen

cycle?

Who Cares About DIRT?

How is my food choice impacting the environment?

How come not everyone has enough food?

About 38% of Earth’s land surface is used for agriculture.

Section 1 Soil• Explain how soil is formed.• Describe the different layers

(horizons) of soil.• List four characteristics used to

classify soil.

What is soil made of?• Soil is made up of

minerals, organic matter, air, and water.

• Soil composition is influenced by climate, organisms, landforms, parent material, and time

Soil Composition • Soil is a thin layer

over most land that is a complex mix of rock, nutrients, decaying matter, water, air and billions of organisms…many microscopic decomposers

Why is soil important?• Renewable

resource…SLOW• Depends upon

climate (1cm in 15yrs.)

• Basis of life• Filters water• Water storage• Habitat

Simplified Soil Food Web

Soil Formation•Weathering: Physical and

chemical breaking of rocks and minerals into smaller pieces

•Erosion and deposition: Pick-up, transport, and drop-off of material from one place to another

•Decomposition: Breakdown of waste, organisms, and organic material into simple molecules

Weathering of PARENT MATERIAL (ROCK)

Soil Horizons• Soil horizons are

distinct layers of soil.

• A cross-section of soil horizons is a soil profile.

• “A” Most Critical

Did You Know? In general, organic matter is concentrated in the O and A horizons, making them the most critical for agriculture.

Soil Characteristics • Soil groups are

further classified according to properties such as color, structure, pH, and texture.• Soil texture is based

on particle size.

Topsoil Color a Great Quick Indicator

Dark, loamy, neutral pH are some of best soils for farming

Dark color often means lots of decayed material (nutrients)

Section 1 Review

• Explain how soil is formed.• Describe the different layers

(horizons) of soil.• List four characteristics used to

classify soil.

Section 1 Quiz

1) After a catastrophe, soil formation is the first step in• A. primary succession. • B. secondary succession. • C. a climax community.

2) Most of the nutrients in soil come fromA. chemical weathering. B. mechanical weathering. C. erosion. D. decomposition.

3) A farmer interested in raising healthy crops should look for aA. heavy clay soil with a high pH and a dark color. B. loamy soil with a low pH and a light color.C. loamy, clumpy soil with a neutral pH and a dark color. D. sandy soil with a high pH, no clumps, and a light color.

4) An example of a soil parent material isA. humus. B. volcanic rock. C. leaf litter. D. topsoil.

5) As a farmer, you would be most concerned with the quality of the soil in theA. O horizon. B. A horizon. C. E horizon. D. R horizon.

6) A rancher interested in the quality of the soil in her pasture might use which aspect of soil as a quick indicator of the pasture’s overall fertility?A. color B. smell C. structure D. pH E. Taste

7) Short Answer: If you were to travel to the desert in Arizona, you might find Horizon Layer O and A missing. Why?

8) Short Answer: What determines how quickly Horizon O and A form?

Some estimates predict that 50 million people could be displaced in the next 10 years due to desertification, a form of soil degradation.

Section 2 Soil Degradation and Conservation

• What causes soil erosion?• How serious of a problem is it?• What are ways that farmers,

ranchers and forestry lead to soil erosion?

Causes of Soil Erosion

Wind

Water #1

People

Soil Erosion

• Often occurs faster than soil is formed, depleting fertile topsoil• Crops, trees, and

other plant communities protect soil from erosion.

Did You Know? More than 19 billion hectares (47 billion acres) of the world’s croplands suffer from erosion and other forms of soil degradation resulting from human activities.

Impacts of Soil Erosion• Loss of soil fertility• Sediment runoff causes

problems in surface water (pollution, clog ditches, boat channels, reservoirs)

• #1 source of U.S. water pollution

• Renewable only on LONG timeframes (200-1,000yrs. for 1 inch)

What time of year do you think most farm fields in U.S. are vulnerable to erosion?

On Ag. land in U.S. today, soil is eroding 16 times faster than it is created

Areas of serious concern

Areas of some concern

Stable or nonvegetative areas

Farming Practices That Reduce Erosion

• Intercropping: Different crops mixed together

• Crop rotation: Crops are alternated.

• Shelterbelts: Tall plants block wind.

• Conservation tillage: Soil turnover is reduced.

• Terracing: Steep slopes turned into “steps”

Tillage vs. Conservation Tillage

Contour and Strip Cropping

Ranching Practices• Ranching is the raising and

grazing of livestock.

• Overgrazing causes and worsens many soil problems.

• Range managers encourage grazing limits and enforce them on publicly owned land.

Forestry Practices• Forestry practices,

such as clear-cutting, can increase erosion.

• Today, practices that reduce soil erosion, such as selective logging, are increasingly common.

Soil Pollution• Too much, or carelessly

timed irrigation can waterlog crops and lead to salinization—a buildup of salts in upper soil horizons.

• Toxic pesticides can remain in soil for a long time, eventually filtering to groundwater.

EvaporationTranspiration

Evaporation

Waterlogging

Less permeableclay layer

Desertification

Soil Salinization

Soil Pollution

Section 2 Review

• What causes soil erosion?• How serious of a problem is it?• What are ways that farmers,

ranchers and forestry lead to soil erosion?

Humans have been practicing agriculture for about 10,000 years.

What is that?

Aldo Leopold

There are two spiritual dangers in not owning a farm. One is the danger of supposing that breakfast comes from the grocery store, and the other that heat from the furnace.

Section 3 Agriculture

• Describe the history of farming.• Analyze the costs and benefits of the “Green

Revolution”• What are some ways farmers control weeds

and pests?• Why are pollinators important to farmers?

What are some of the ecological and economic services that croplands provide? (what good are farms?)

The Beginnings of Agriculture

People were hunter-gatherers through most of human history, until agriculture developed about 10,000 years ago.

Why 10,000 years ago?

Agriculture History• In early agriculture,

people began planting seeds from plants they liked most

• Agriculture and livestock provided a stable food supply, which allowed the development of modern civilization.

Types of Agriculture

• Traditional Agriculture

Industrial Agriculture

The Green Revolution• Introduced new technology, crop

varieties, and farming practices to the developing world in the mid- to late 1900s

Benefits:

• Increased crop yields and saved millions of people from starvation in India and Pakistan

• Prevented some deforestation and habitat loss by increasing yields on cultivated land

Green RevolutionCosts:• Led to a 7000% increase in energy used by

agriculture

• Worsened erosion, salinization, desertification, eutrophication, and pollution

Pests and Weed Control (Farmers Enemies)

• Chemical pesticides: Effective and cheap, but can lead to resistance

•Biological pest control: Permanent solution, but can harm nontarget organisms

•Integrated pest management: Increasingly popular solution, combines chemical and biological pest-control methods

Pests and Weed Control

Cactus moth larvae are used to control prickly pear cactus, but also threaten many rare, native cacti around the world.

Pollinators• Agriculture relies on

pollinators, such as insects.

• Native and domesticated pollinator populations have declined due to pesticide use, parasites, and other as-of-yet unknown causes

Section 3 Review

• Describe the history of farming.• Analyze the costs and benefits of the

“Green Revolution”• What are some ways farmers control

weeds and pests?• Why are pollinators important to

farmers?

• Each year, Earth gains 75 million people and loses 5–7 million hectares of productive cropland.

Section 4: Food Production

• How is our food produced and what impact does that food production have on our environment?

• What are GM foods?• What does sustainable food production

look like?

Human NeedsLarge amounts of

macronutrients (protein, carbs, fats)

Small amounts of micronutrients (A, C, E, iron, iodine, calcium)

• Chronic under nutrition: disease increase, stunted growth etc.

• Malnutrition: can not get enough protein mainly eating corn, rice, wheat

• Huge childhood problem

MalnutritionUN Estimates:• 5.5 million each year die

prematurely due to effects of under nutrition.

• Each day 15,100 people --- 80% of which are children

• In U.S. estimates are 11 million do not have access to enough food

Over nutrition Food intake exceeds

energy use and causes body fat

• Too many calories not enough exercise

• Lower life expectancy, heart disease, lower productivity and quality of life

• In developed countries it is 2nd leading preventable cause of death after smoking

Food SecuritySince 1960, our ability to produce food has grown faster than the human population, but 1 billion people are hungry worldwide.

Malnutrition and undernourishment are most common in the developing world.

Arable Land

• Land suitable for farming

• Running out• Loosing soil

Genetically Modified OrganismsOrganisms that have had their DNA modified

Commonly engineered traits include rapid growth, pest resistance, and frost tolerance.

In the United States, 85% of corn and 90% of soybean, cotton, and canola crops come from GM strains.

Risks and Benefits of GM Crops

Potential for “superpests” that are resistant to pest-resistant cropsContamination of non-GM plants

Benefits of GM Crops

•Benefits:•Insect-resistant crops reduce the need for insecticides.•Herbicide-resistant crops encourage tillage conservation.

Industrial Food Production: Feedlots

Alternative to open grazing in which energy-rich food is delivered to a concentrated group of livestock or poultry

Benefits and Cost of Feedlots (Factory Farms)

Benefits: Reduces soil degradation and fertilizer use

Costs: Requires antibiotic use; potential for water contamination and animal stress

What is this?

Industrial Food Production: Aquaculture

Fish farming in a controlled environment

Benefits and Costs of AquacultureBenefits: Can be sustainable; reduces by-catch; reduces fossil fuel useCosts: More difficult to control spread of diseases; produces a lot of waste; potential for farm-raised animals to escape into wild

Sustainable Agriculture• Does not deplete soil

faster than it forms• Does not reduce the

amount or quality of soil, water, and genetic diversity essential to long-term crop and livestock production

Sustainable Agriculture • Organic agriculture is

sustainable agriculture that does not use synthetic chemicals.

• Local, small-scale agriculture reduces the use of fossil fuels and chemicals used for transportation and storage.

U.S. Food travels avg. of 1,500 miles from farm to fork in U.S.

New Jersey Peach Farm: What are the advantages and disadvantages of eating locally grown food?

Section 4 Review

• How is our food produced and what impact does that food production have on our environment?

• What are GM foods?• What does sustainable food production

look like?

Section 4 Quiz

1) Agriculture most likely began• A. 10,000 years ago in the Middle

East. • B. 200,000 years ago in Africa.• C. 15,000 years ago in China.

D. 150,000 years ago in Egypt.

2) Genetic engineering relies on placing a gene that codes for a desired trait into the __________ of a different organism from the organism where the gene was originally harvested.A. protein B. amino acid C. helix D. genome

3) Your friend tells you she’s decided not to use pesticides or synthetic chemicals on her farm; instead she’ll rely on composting and biological pest control. She is practicingA. industrial agriculture. B. monoculture. C. organic agriculture. D. sustainable agriculture.

4) Sustainable agriculture is important because while human population continues to grow, which of the following will not?A. animal population B. arable land C. food production D. GM crops

5) What event enabled the evolution of agriculture?A. a warming climate due to volcanic eruptions in IndonesiaB. a sudden growth in human populationC. a decrease in natural prey species, such as large hooved mammalsD. a warming climate, which ended an ice age

6) A large area of cropland seeded with one crop is a(n)A. monoculture. B. polyculture.C. organic practice. D. traditional farming technique.

7) A farmer has an infestation of aphids and greenflies. He introduces ladybugs, which prey on aphids, and uses a limited dose of a pesticide to deal with the flies. The farmer’s approach to insect pests isA. chemical control. B. biological control.C. integrated pest management. D. organic pest management.

8) You would expect to find most farmers who use GM crops living inA. relatively poor, undeveloped countries. B. countries with strong environmental protection laws.C. countries with weak environmental laws. D. relatively wealthy, developed countries.

9) The average food item in the United States travels 2400 km to reach the buyer. One alternative to this energy-inefficient practice isA. treating the food with preservative chemicals. B. buying locally produced food.C. buying organic food. D. buying GM food.

10) GM foods are engineered to resist herbicides so thatA. humans won’t be put at health risk from pesticides. B. insect pests will avoid the crops.C. the crops will grow more efficiently. D. farmers can use heavier doses of pesticides for weeds without killing the crop plants.

11) In the Chart, which is the most efficient source of animal protein?

12) Chart B illustrates energy transfer and trophic structure in a natural ecosystem. If this

was an agriculture ecosystem, where would humans be located?