Soil Use and Abuse

Chapter 11APES January 2007

Objectives Define the roles of living organisms,

physical forces, and other factors on creating and maintaining fertile soil.

Differentiate between the sources and effects of land degradation including erosion, nutrient depletion, waterlogging, and salinization.

SO what does that really mean? How is soil made? How is it destroyed? What role are we playing as humans?

What is soil?Soil is made of three things: Water Eroded rock material Dead stuff Live stuff

The water componentThe moisture content of the soil will depend

upon several factors:

How well drained the soil is The rock composition/particle size How much it rains

The rock component Bigger rock particles such as gravel and

sand (see chart page 237) provide good drainage and aeration. It’s easier for roots to push through this type of soil.

Smaller rock particles such as clay and silt tend to pack and offer less air spaces, but are better at holding the minerals.

Humus (dead stuff) in the soil The dead animal and plant parts in soil act

like a sticky glue holding the tiny rock particles together, making the spongy conditions needed for roots to grow.

It also holds the water and minerals needed by plants.

Soil Organisms in the soil

Soil aeration by worms and bugs Decomposing humus by fungi and bacteria Algae makes new organic compounds Burrowing mammals help aerate as well Plant roots penetrate the soil and secrete

acids, breaking down rock further

The Soil Profile/Soil HorizonsField trip flashback:

Remember allThe differences?

The E layer is alsoCalled the Zone of Leaching

Types of Soils Your text discusses the types of soils,

please study them pg. 238-239.

12 soil orders, I will discuss three common to WI. You should be aware of and be able to discuss the rest.

Mollisols: under grasslands

Spodosols: under pine forests

Alfisols: deciduous forests

How do we use our soil? 11% of our land areas is under agriculture. 4 times that could be crops but it would

affect the wildlife populations.

Many areas cannot support agriculture due to soil chemistry, topography, and rainfall.

How are we using our land? Land use comparison Wisconsin land use Satellite land use

Study chartPage 240Of your text.

Land use correlations Developed countries through technology

are tilling less land.

Developing countries are destroying forests to create agricultural areas that are not sustainable.

2/3 crop gains have come from better genetics and methods.

Ecological Trade offsBe sure to read about the challenges facing

developing countries.

How do you decide between saving the rainforest and feeding your people?

Just because you CAN cultivate land SHOULD you?

The Sad Truth about some areas:When you clear the trees from the land And there isn’t very deep soilAnd there’s lots of rain

You have about 5 years Until the soil is ALL goneWashed away

It will take 100s of years to rebuild.

If we acted as a team….

There’s plenty of land that COULD be farmed safely and we could feed the world.

I have often thought….what if we tried to feed the world as hard as we are trying to liberate Iraq? What would happen?

Degradation of the LandWhat does that really mean?

It means the land gets ruined.Hmmm…..how?

Fertilizers , overgrazing, and erosion. Why does that happen?

Every year our land takes a hit: 3 million hectares are ruined by erosion 4 million hectares are turned into desert 8 million hectares are turned into

something other than crop land such as malls, homes, highways and parking lots

World Statistics on Land Degradation: 3oo million hectares: strongly degraded 910 million hectares: moderatelydegraded 9 million hectares: not usable anymore

Causes:Water, wind, salts

Signs of Degradation:Soil is impoverished or eroded

Signs of Degradation:Water runs off the land or is contaminated

Signs of Degradation:Vegetation is diminished

Signs of Degradation:Biomass production is decreased

Signs of Degradation:Wildlife diversity diminishes

Impacts:Ranches: fewer livestockFarms: poor crop yieldsNature: less species

Page 241 of the text shows the percentages of degradation by country and region.

Major Issues to Tackle:Water 55%Wind 29% these happen naturally

but can be exacerbatedChemical 12%Nutrient depletion, Salinization, acidification,

pollution

Physical 4%Heavy machinery, cattle, waterlogging,

solidification

What exactly is erosion?It’s the transport of soil from one place to

another.

How does it happen?Wind and Water carrier soil parts from high

places to low places.

It has shaped the surface of our planet.Is it really bad?

Wind Erosion

Wind Erosion

Wind

Wind

Water Erosion

Water Erosion across the World

Types of Erosion Rill ErosionTiny rivers of running water make small

channels in the soil

Gully ErosionRills enlarge to form big channels in the soil

Where is it happening? Agricultural Fields/runoff

The fields loose soil twice as fast as it is being replaced.

Dust StormsWind carries the soil away and dumps it

elsewhere. This can be worse than water in some ways.

US and Canada are big culprits Intensive cropping/row crops Deep plowing Heavy herbicide applications Machines create gullies Abandonment of crop rotations/$$ issues Monoculture cropping check out these stats in your text pg. 242

What are we to do?You tell me gang.What can we do as individuals to help stop

the washing away of our future?