15.2 Objectives

Distinguish between traditional and modern agricultural techniques.

Describe fertile soil. Describe the need for soil conservation. Explain the benefits and environmental impacts of

pesticide use. Explain what is involved in integrated pest

management. Explain how genetic engineering is used in

agriculture.

Agriculture: Traditional

The basic processes of farming include plowing, fertilization, irrigation, and pest control.

Plows were pulled by livestock. Organic fertilizers, such as manure, enrich the soil. Fields are irrigated by water flowing through ditches.

Agriculture: Modern

Machinery powered by fossil fuels plows the soil and harvests crops. Synthetic chemical fertilizers have replaced manure and plant wastes to fertilize soil.

A variety of overhead sprinklers and drip systems are used for irrigation. Synthetic chemicals are used to kill pests.

Video: I’m Farming and I Grow It

Arable land is farmland that can be used to grow crops.

Soil that can support the growth of healthy plants is called fertile soil.

Topsoil is the surface layer of the soil, which is usually richer in organic matter than the subsoil is.

Fertile topsoil is composed of living organisms, rock particles, water, air, and organic matter, such as dead or decomposing organisms. Several layers of soil lie under the topsoil. The bottom layer is bedrock, which is the solid rock from which most soil originally forms.

Fertile Soil: The Living Earth

Fertile Soil: The Living Earth

Soil forms when rock is broken down into smaller and smaller fragments by wind, water, and chemical weathering.

It can take hundreds or even thousands of years for these geological processes to form a few centimeters of soil.

Fertile Soil: The Living Earth

Rock particles supply mineral nutrients to the soil.

Fungi and bacteria decompose dead plants as well as organic debris and add more nutrients to the soil.

Earthworms, insects, and other small animals break up the soil allowing air and water into it.

Soil Erosion: A Global Problem

Erosion is a process in which the soil is loosened, dissolved, or worn away by wind, water, ice, or gravity.

In the U.S., about half of the original topsoil has been lost to erosion in the past 200 years.

Without topsoil, crops will not grow. Yet, almost all farming methods increase the rate of soil erosion.

Land Degradation

Desertification is the process by which human activities or climatic changes make arid or semiarid areas more desertlike.

Soil Conservation

There are many ways of protecting and managing topsoil and reducing erosion.

Soil usually erodes downhill, and many soil conservation methods are designed to prevent downhill erosion.

Soil-retaining terraces can be build across a hillside. On gentler slopes, contour plowing, plowing across the slope of a hill instead of up and down the slope, can be used.

Soil Conservation

An even more effective method of plowing is strip planting leaving strips of vegetation across the hillside instead of plowing the entire slope. These strips catch soil and water that run down the hill.

In no-till farming, a crop is harvested without turning the soil over, as in traditional farming.

Enriching the Soil

Inorganic fertilizers that contain nitrogen, phosphorous, and potassium have changed farming methods. If erosion occurs in these areas, waterways may become polluted.

A modern method of enhancing the soil is to use both organic and inorganic materials by adding compost and chemical fertilizers to the soil.

Compost is a mixture of decomposing organic matter, such as manure and rotting plants, that is used as fertilizer and soil conditioner.

Salinization

The accumulation of salts in the soil is known as salinization.

Salinization is a major problem in places that have low rainfall and naturally salty soil.

When water evaporates from irrigated land, salts are left behind.

Environmental Science 4/1

ARW pg 81-82 (10 min) 15.2 notes/ Learning Objectives (20 min) Ticket out the door --

Pest Control Worldwide, pests destroy about one-third of the

world’s potential food harvest. A pest is any organism that occurs where it is not

wanted or that occurs in large enough numbers to cause economic damage.

A pesticide is a poison used to destroy pests, such as insects, rodents, or weeds; examples include insecticides, rodenticides, and herbicides.

More than 500 species of insects have developed resistance to pesticides since the 1940s.

Pollution and Persistence

A pesticide is persistent if it does not break down easily or quickly in the environment.

Persistent pesticides do not break down into harmless chemicals, and they accumulate in the water and soil.

Some pesticides have been banned in the United States for decades but can still be detected in the environment. DDT is an example

Biological Pest Control

Biological pest control is the use of certain organisms by humans to eliminate or control pests.

Biological pest control includes the use of pathogens, plant defenses, chemicals from plants, and the disruption of insect breeding

Integrated Pest Management

Integrated pest management is a modern method of controlling pests on crops.

The goal of integrated pest management is not to eliminate pest populations but to reduce pest damage to a level that causes minimal economic damage.

Such programs can include a mix of farming methods, biological pest control, and chemical pest control.

Integrated Pest Management

Engineering a Better Crop

Genetic engineering is a technology in which the genome of a living cell is modified for medical or industrial use.

Scientists may use genetic engineering to transfer desirable traits, such as resistance to certain pests, from one organism to another.

Plants that result from genetic engineering are called genetically modified (GM) plants.

Video

Sustainable Agriculture

Farming that conserves natural resources and helps keep the land productive indefinitely is called sustainable agriculture.

Sustainable agriculture involves planting productive, pest-resistant crop varieties that require little energy, pesticides, fertilizer, and water.

15.2 Objectives con’t; Write and answer on back.

Explain the benefits and environmental impacts of pesticide use.

Explain what is involved in integrated pest management.

Explain how genetic engineering is used in agriculture.

Explain how sustainable agriculture and low input farming are beneficial.