Bellringer

• What types of crops are appropriate for our area?

• What things would be needed for a healthy crop?

Crops and SoilSection 15.2

Objectives:1. Describe land-use practices that promote

sustainability and economic growth.2. Identifying ways to manage waste.3. Describe the composition of soil profiles.4. Identifying various processes and activities that

promote soil formation.5. Describe agents of erosion and methods for

preventing soil erosion.

Agriculture• Arable land: see your vocabulary for def.

Basic farming process

Traditional

methods

Modern methods

Plowing Read p.384 to fill in this chart

Fertilization

Irrigation

Pest control

Fertile Soil

• Can support healthy plant growth• Topsoil:

– surface layer of soil; – usually richer in organic matter than the

subsoil; – where plant roots grow

• Formation of fertile soil:– Weathered rock particles supply mineral

nutrients.– Fungi and bacteria for decomposition– Earthworms, insects, and small animals

break up the soil, allowing air and water into it.

Soil Profile (Fig. 8, p.385)

Assignment

• Fold your paper in half hotdog style.• Draw and color a soil profile showing

details of all 6 layers. (Your drawing should take up the whole front of your folded paper.)

• Cut the layers apart, creating 6 flaps.• On the inside, label and describe each

layer. (Example: O Horizon/Surface litter – fallen leaves and dead animals)

Soil Erosion and Land Degradation

• Erosion: the wearing away of rock or soil by wind or water

• In the U.S., ½ the topsoil has been lost to erosion in the past 200 years. Why is this a problem?– It takes a long time to form soil.– Without fertile topsoil, crops cannot be

supported. Most farming methods make erosion worse!!!

• Land degradation – damaging land so that it can no longer support the local ecosystem.

Soil Erosion and Land Degradation (cont.)

• Desertification: the process by which land in arid or semiarid areas becomes more desertlike

• Human causes of desertification:– Overplanting – planting too many crops too

frequently– Not enough fallow time (when land is left

unplanted to allow it to recover)– Overgrazing , which eliminates plants that

hold topsoil in place

Real-Life Examples

•Northern Africa•Dust Bowl, 1930’s

Soil Conservation Methods

• In which direction would soil erode on any degree of slope?

• Ways to reduce erosion on sloped land:– Terracing – stairsteps of level field areas

going up a hill– Contour plowing – plowing along the natural

contour of the land

Soil Conservation Methods (cont.)

• No-till farming: – Leave crop remains to hold soil in place.– Also saves time– Soil may become too densely packed and

lower crop yields.

Enriching the Soil

• Traditionally vs. Chemically– Advantages of each– Disadvantages of each

• Compost: partially decomposed organic material (both plant and animal!)

Salinization:

• Def.: the accumulation of salts in soil

• A problem in areas of low rainfall– Irrigation water comes from rivers or

groundwater (saltier than rainwater)– When water evaporates, the salts remain

behind, accumulating in the soil.– Too much salt = plants cannot grow

Assignment

• Both wars and drought can lead to famine. In what ways do they have similar effects, and in what ways are their effects different?

• Write a paragraph to explain your answers.

Pest Control

• In North America, pests destroy about 13% of all crops; in Kenya, more than 25%; more than 33% worldwide.

• Why the differences?• Pest: any organism that occurs where

it is not wanted or that occurs in large enough numbers to cause economic damage – NOT limited to insects!

• Pest control is one benefit of crop rotation. (Know why! – p.389)

Pesticides:

• Def.: ???

• Can also harm beneficial plants and insects, wildlife, and people

• Disadvantages of pesticide use:– Pests may develop resistance to chemicals.– Human health concerns (cancer, nervous

system disorders, etc.)– Persistent pesticides (pesticides that do not

break down rapidly) accumulate in the water and soil. (EX; DDT, banned in the ’70’s, still detected in environment and breast milk)

Biological Pest Control:

• Def.: Using living organism to control pests.• All organisms have natural enemies!• Types of biological pest control:

1. Pathogens: organisms that cause disease (EX: Bt, a bactrium, kills caterpillars of moths and butterflies)

2. Plant defenses: chemical compounds that repel insects, plants barriers such as tougher skin

3. Disrupting insect breeding• Growth regulators: interfere with some stage of an

insect’s life cycle• Pheromones: can be used to confuse mating

habits• Expose males to x-rays to sterilize them

Genetic Engineering:

• Def.: genetic material in a living cell is modified for medical or industrial use

• Plants created by genetic engineering are called genetically modified (GM) plants.

• These plants are usually bred for their resistance.

Sustainable Agriculture

• What do you think the phrase “sustainable agriculture” means?

• What techniques/products/resources do you think would be limited (used in limited amounts or not at all) in this type of farming?

• What techniques would be used more?

GM Foods Project Assignment