You need your notebooks and be finishing up your comic

strip.

Erosion

6.4 billion tons of soils are eroded from the U.S. each year; this would fill 320 million average-sized dump trucks that, if parked end-to-end, would extend to the moon and ¾ of the way back!

A. Erosion

Definition

Erosion is the movement of soil components, especially surface litter and topsoil, from one place to another.

Importance

In undisturbed ecosystems, the roots of plants help anchor the soil, and usually soil is not lost faster then it forms.

But, farming, logging, construction, overgrazing by livestock, off-road vehicles, deliberate burning of vegetation etc. destroy plant cover and leave soil vulnerable to erosion. This destroys in a few decades what nature took hundreds to thousands of years to produce.

SOIL EROSION AND DEGRADATION

Soil erosion lowers soil fertility and can overload nearby bodies of water with eroded sediment.

B. Types of Erosion1. Sheet erosion: surface water or wind peel off thin layers

of soil.

2. Rill erosion: fast-flowing little rivulets of surface water make small channels.

3. Gully erosion: fast-flowing water join together to cut wider and deeper ditches or gullies.

4. Surface Creep – mountains/sand dunes; surface creeping slowly across. Landslides are an example of a very fast surface creep.

Wind Erosion

Saltation – one particle hitting another and being blown across the surface of the soil.

Suspension – airborne soil. Ex. soil from Lubbock is found in Temple, Texas.

Gully – rivulets of fast-flowing water join together and, with each succeeding rain, cut the channels wider and deeper until they become ditches or gullies. Gully erosion usually happens on steep slopes where all or most vegetation has been removed.

Global Outlook: Soil Erosion

Soil is eroding faster than it is forming on more than one-third of the world’s cropland.

Figure 13-10Figure 13-10

C. Other ways we affect soil…

1. Desertification: Degrading Drylands

About one-third of the world’s land has lost some of its productivity because of drought and human activities that reduce or degrade topsoil.

Figure 13-12Figure 13-12

2. Salinization and Waterlogging

Repeated irrigation can reduce crop yields by causing salt buildup in the soil and waterlogging of crop plants.

Figure 13-13Figure 13-13

Fig. 13-13, p. 281

EvaporationTranspiration

EvaporationEvaporation

Waterlogging

Salinization Waterlogging1. Irrigation water contains small amounts of dissolved salts

2. Evaporation and transpiration leave salts behind.

3. Salt builds up in soil.

1. Precipitation and irrigation water percolate downward.

2. Water table rises.

Less permeable clay layer

Salinization and Waterlogging of Soils: A Downside of Irrigation

Example of high evaporation, poor drainage, and severe salinization.

White alkaline salts have displaced cops.

Figure 13-14Figure 13-14

D. Erosion Control

1. Shelterbelts or Windbreaks– can reduce wind erosion. Long rows of trees are planted to partially block the wind. They can also help retain soil moisture, supply some wood for fuel, and provide habitats for birds.

2. Minimum Tillage – (conservation tillage) to disturb the soil as little as possible while planting crops.

Special tillers break up and loosen the subsurface soil without turning over the topsoil, previous crop residues, and any cover vegetation.

Modern farm machinery can plant crops without disturbing soil (no-till and minimum tillage.

Conservation-tillage farming:• Increases crop yield.

• Raises soil carbon content.

• Lowers water use.

• Lowers pesticides.

• Uses less tractor fuel.

3. Contour Farming –sloping your growing crops, etc.

You run terraces parallel to the ground to stop soil from running down a steep slope. Plowing and planting crops in rows across, rather than up and down, the sloped contour of the land.

4. Terracing – (what you use for contour farming.) Dirt goes up to hold the dirt in place. Broad, nearly level terraces that run across the land contour. Helps to retain water for crops at each level and reduce soil erosion by controlling runoff.

5. Strip Cropping – a row crop such as corn alternates in strips with another crop that completely covers the soil, reducing erosion. It catches and reduces water runoff and helps prevent the spread of pests and plant diseases.

6. Cover Cropping (alley cropping) – several crops are planted together in strips or alleys between trees and shrubs that can provide shade (which reduces water loss by evaporation) and helps to retain and slowly release soil moisture.

7. Crop Rotation

Planting a series of different crops in the same field. Opposite of what the settlers did in early US history.

A study showed that a field using a corn-wheat-clover rotation lost an average of 2.7 tons of top soil per year

A field just planting corn year after year = 19.7 tons.

Definition

Hydroponics are growing plants in fertilized water.

8. Hydroponics:

Method of suspending plants in water and the solutions involved.

Ex. cranberries are grown this way.

Costs of Hydroponics:

It is labor-intensive and expensive.

You can control the environment & grow plants where there is no soil; NASA is looking into this.

Benefits: