Soil

Abuses and Conservation

Case Study (Cunningham)

Farming the Cerrado

Good soil for planting or bad?

Good soil for planting or bad?

Good soil for planting or bad?

Good soil for planting or bad?

Abuses of Soil

There are 3 main ways that soil is degraded. Erosion Toxification Salinization

Erosion

Abuse--Soil Erosion There are 3 different kinds of erosion of soil.

Water Wind Ice (caused by glaciers)

Worldwide, erosion removes 25.4 billion metric tons of soil per year. Made worse by deforestation and desertification. Poor agricultural practices increase erosion and

lead to the transport of associated fertilizers and pesticides.

Erosion

We are going to talk only about wind and water erosion in this power point

Water Erosion

Water erosion caused by exposed soil when native

plants are removed from the site. Examples: deforestation, building sites,

clearing for crops.

Water Erosion Water erosion

results in siltation (filling up of waterways with soil) and can unnaturally speed up ecological succession.

Water Erosion

How people use soil in Madagascar.

Rice fields in Madagascar

Deforestation in Madagascar

Results of Soil Abuse

Water Erosion

Worldwide soil erosion

Wind Erosion

Wind erosion may not be as evident as water erosion, but is still serious. It is most common in dry, treeless

areas. Great Plains of North America have

had four serious bouts of wind erosion since European settlement in the 1800s.

Wind Erosion

Wind erosion is caused when plant cover and surface litter are removed by agriculture or grazing Examples: deforestation, building sites,

clearing for crops. Results in desertification

Windblown dunes encroach on useful land China has lost 93,000 square kilometers (the

size of Indiana) to desertification. 170 million acres of U.S farmland is degraded.

Toxification

Abuse--Toxification Toxification is caused when modern

agriculture sprays toxic chemicals to kill or drive away pests (insects or weeds). Examples are pesticides and herbicides

have doubled the crop yield. Results in:

Killing nontarget species Creating new pests or organisms Pesticide resistance Pollution of waterways

Abuse--Toxification 73% of conventionally grown foods

have residues from at least one pesticide.

23% of organics have residues

Abuse--Toxification Consequences to human health:

disrupt endocrine hormone functions causes spontaneous abortions, low birth weights and neurological disorders, increases cancer rates, developmental defects among infants.

Consequences to animal health: Severe reproductive effects in amphibians

Salinization

Abuse--Salinization Salinization is caused by too much

irrigation which leads to waterlogged soil. Salinization results in mineral salts

accumulating in the soil (due to the fact that irrigation water contains some salt).

This results in leaving behind a crusty layer of salt

Consequence: Lethal to plants (think osmosis)

Conservation

Soil Conservation Practices

Agricultural Potential Worldwide:

11% of land surface is suitable for crops (arable). An additional 24% is in permanent pasture for

livestock. United States:

20% land surface is arable. 25% in permanent pasture.

African Continent: 6% land surface suitable for crops. 29% can be used for pasture.

Soil Conservation Practices When topsoil is lost, fertility is reduced or

destroyed, thus fertilizers must be used to restore fertility. This practice raises food costs, and increases

sediment load in waterways. Fertilizers change the nutrient level in waterways

and ground water which leads to a change in water ecosystems.

Over 20% of U.S. land is suitable for agriculture, but only 2% does not require some form of soil conservation practice.

Soil Conservation Practices Soil Quality Management Components:

Manage pests and nutrients efficiently. Prevents toxification

Prevent soil compaction. Plants don’t grow in compacted soil.

Diversify cropping systems. Keeps nutrients from being drawn out of the soil.

Soil Conservation Practices

Ways to prevent soil erosion include Avoid excessive tillage (upturning). Keep the ground covered. Use different cultivation techniques Wind breaks

Soil Conservation Practices Ways to prevent toxification.

Enhance organic matter. Increases topsoil

Add lime (gypsum—a type of mineral) increase pH if soil is acidic

Don’t overuse pesticides and herbicides

Soil Conservation Practices

Ways to prevent salinization: Don’t over water.

Use technology like drip irrigation or downward-facing sprinklers.

Alternative Cultivation

Draw an arrow to the picture that represents each type of alternative cultivation

Soil Conservation Practices—Alternative Cultivation Contour farming is tilling at right

angles to the slope of the land. Each ridge acts as a small dam. Useful on gentle slopes. One of the simplest methods for

preventing soil erosion. Strip farming is the practice of

alternating strips of closely sown crops to slow water flow, and increase water absorption.

Soil Conservation Practices

Terracing is the practice of constructing level areas at right angles to the slope to retain water. Good for very steep land.

Case Study (Enger 13.3 pg. 306 and 309)

Land Capability Classes Global Perspective Soil Fertility and Hunger in Africa