Monday (1/23/2012)Let’s Get Dirty

Today’s Agenda: 1. Journal Question: Why is soil

composition important?2. *Lecture I: Soil – Foundation of

Land Ecosystems3. Final Exam next Monday (100

Questions) – Good Luck!4. Free Response Questions next

Tuesday (2 Questions) –Good Luck!

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2004 AP Environmental Exam Report for Perspective

Multiple-Choice Portion of ExamFundamental Principles & Concepts: 25

QuestionsHuman Population: 12 QuestionsResource Distribution & Use: 13

QuestionsEnvironmental Quality: 24 QuestionsGlobal Changes: 12 QuestionsSocial & Economic Forces: 13 Questions

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2004 AP Report Environmental Exam for Perspective

Free-ResponseHeavy Metals In SeafoodWind Power Cost AnalysisRadioactive Isotopes-WasteSoils-Analysis & Conservation

Soil Particles are Quite SmallIn fact, one could say they are mini

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Soil: Foundation for Land Ecosystems A. Soil & Farmland

1. 90% of the world’s food comes from land-based agricultural systems, and the percentage is growing as the ocean’s fish and natural ecosystems are increasingly depleted. 2. As the world’s population moves beyond 7 billion, croplands and grazing lands are being increasingly pressed to yield more crops and other products.

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Agriculture PracticesA. The poor agricultural

practices of the past 50 years have led to the degradation of 23% of land used for crops, grazing, or forestry.

Agriculture Practices B. Throughout the world, agricultural soils have

been (and continue to be) degraded by erosion, the build up of salts, and other problems that can only undermine future productivity.

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Loss of Prime FarmlandA. In the United States, another kind of agriculture

land loss has occurred: The loss of prime farmland.

B. This is happening because farmlands are usually easy to develop and farmers can often sell their land to developers at huge profits.

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Productive SoilA. Detritus feeders and

decomposers constitute a biotic community of organisms that not only facilitate the transfer of nutrients, but also creates a soil environment that is most favorable to the growth of roots.

B. A productive topsoil involves dynamic interactions among the organisms, detritus, and minimal particles of the soil.

SoilA. Soil covers much of the land on Earth.

It is made up of minerals (rock, sand, clay, silt), air, water, and organic material (matter from dead plants and animals).

B. Soil provides a substrate for plants (roots anchor in soil), a source of food for plants, and a home for many animals (insects, spiders, centipedes, worms, burrowing animals, bacteria, and many others).

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Someone that studies soil is called…Pedologist

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Soil FormationA. Soil Formation: Soil is formed slowly as rock

(the parent material) erodes into tiny pieces near the Earth's surface. Organic matter decays and mixes with inorganic material (rock particles, minerals and water) to form soil.

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Soil HorizonsA. Soil Horizons (layers): Soil

is made up of distinct horizontal layers; these layers are called horizons.

B. They range from rich, organic upper layers (humus and topsoil) to underlying rocky layers ( subsoil, regolith and bedrock).

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Soil Profiles: The process of soil formation creates distinct

horizontal layers of soil:O Horizon: Humus (surface litter, decomposing plant

matter). Humus = residue of partly decomposed organic material.

A Horizon: Topsoil. (mixed humus and leached mineral soil)

E Horizon: Zone of leaching (less humus, minerals resistant to leaching)

B Horizon: Subsoil (accumulation of leached minerals like iron and aluminum oxides)

C Horizon: Weathered parent material (partly broken-down minerals; glacial deposits, etc.)

-A vertical slice through the different horizons is called the soil profile.

O Horizon O Horizon - The top, organic

layer of soil, made up mostly of leaf litter and humus (decomposed organic matter).

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A Horizon A Horizon - The layer called

topsoil; it is found below the O horizon and above the E horizon.

(1) Seeds germinate and plant roots grow in this dark-colored layer. (2) It is made up of humus (decomposed organic matter) mixed with mineral particles.

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E Horizon E Horizon - This eluviation

(leaching) layer is light in color; this layer is beneath the A Horizon and above the B Horizon.

(1) It is made up mostly of sand and silt, having lost most of its minerals and clay as water drips through the soil (in the process of eluviation).

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Tuesday (January 24) Today’s Agenda:

(1) Journal Question: What is humus?(2) What is eluviation*(3) Soil Horizons Continued & Soil Textures

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B HorizonB Horizon - Also called the subsoil - this layer is beneath the E Horizon and above the C Horizon.

(1) It contains clay and mineral deposits (like iron, aluminum oxides, and calcium carbonate) that it receives from layers above it when mineralized water drips from the soil above.

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C HorizonC Horizon - Also called regolith: the layer beneath the B Horizon and above the R Horizon. (1) It consists of slightly broken-up bedrock. Plant roots do not penetrate into this layer; very little organic material is found in this layer.

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R Horizon R Horizon - The un-

weathered rock (bedrock) layer that is beneath all the other layers.

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Soil Horizons

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Soil Texture

A. All soils exist in layers and can be characterized by their texture.

B. Soil texture; as rock weathers, it breaks down into smaller and smaller fragments.

Soil TextureC. You can see the individual rock particles

in sand, and you can see finer particles in silt, and clay is a gathering of the smallest particles.

D. Sand, Silt, Clay (large to small)E. Sand, silt, and clay particles constitute

the mineral portion of the soil.

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Soil Properties A. Soil texture, porosity (a measure of

the volume of pores or spaces per volume of soil), and permeability (1) The rate at which water and air move from upper to lower layers of soil, determines a soil’s water holding capacity, aeration or oxygen content (the ability of air to move through the soil), and workability (how easily the soil can be cultivated).

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LoamA. A portion that is commonly

found in soil consists of roughly 40% sand, 40% silt, and 20% clay.

B. A soil with these proportions is called loam.

C. Loams are the best soils for growing most crops because they hold lots of water, but not too tightly for plant roots to absorb.

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Sandy SoilsA. Sandy soils are easy to work,

but water flows rapidly through them.

B. They are useful for growing irrigated crops or those with low water requirements, such as peanuts and strawberries.

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Soil & Plant GrowthA. For their best growth, plants need

a root environment that supplies optimal amounts of:1. Minerals2. Water3. Oxygen4. The pH (relative acidity) and salinity (salt concentration) of the soil are also critically important.

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Acidic SoilsA. The uptake of nitrogen and phosphorus by

plants is reduced in acidic soils with a pH below 5.5 and severely reduced in soils with a pH of 4 or lower.

B. When soils are too acidic, the acids can be partially neutralized by an alkaline substance, such as lime.

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Alkaline SoilsA. In dry regions such as much of

the western and southwestern United States, rain does not leach away calcium and other alkaline compounds, so soils in such areas may be too alkaline (ph above 7.5) for some crops.

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Acid Rain’s Effect on SoilA. Burning fossil fuels, especially

coal, releases sulfur dioxide and nitrogen oxides into the atmosphere.

B. These gases form acidic compounds that return to the earth’s surface as acid deposition.

C. As acidic rain or melted acidic snow infiltrates the soil, the result is a loss of soil fertility, which can reduce crops and tree growth, making them more vulnerable to drought, disease, and pests.

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Soil Fertility A. Soil fertility, the soil’s ability to

support plant growth, often refers specifically to the presence of proper amounts of nutrients.

B. Farmers speak of a given soil’s ability to support plant growth as the tilth of the soil.

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LeachingA. Nutrients may literally be

washed from the soil as water moves through it, a process called leaching.

B. Leaching not only lessens soil fertility, but also contributes to pollution when materials removed from the soil enter waterways.

Wednesday (1/25/2012)Today’s Agenda:A. Silent Period:B. Work on Study Guide Questions 1-45.C. AP Exam on Monday (100 Questions)

1/30/12D. Two Essay Prompts on Tuesday 1/31/12

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Thursday (1/26/12) Today’s Agenda:(1) No Talking (-5 or +5)(2) Be in your assigned seat. (-5)(3) What is loam? (4) Finish Soil Lecture III(5) Work on Revised Study Guide for

Final Exam on Monday –Prepare to stay late (make appropriate travel arrangements)

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In the News 2012 Solar flare is a bright and bold ball

of energy that is released from the surface of the sun

A solar flare produces radiation that is hazardous to humans.

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Soil Development A. Soils develop and mature

slowly.B. It can take 200 to 1,000 years

to develop an inch (2.5 cm) of topsoil (A horizon).

Soil Development

C. Well-developed soil profiles, in which distinct O,A,B, and C horizons are visible, are characteristic of older, well-established terrestrial ecosystems.

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Soil Fertility A. A fertile soil that produces

high crop yields has a thick topsoil layer with lots of humus, which helps topsoil hold water and nutrients taken up by plant roots.

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Topsoil Color IndicationsA. The color of the topsoil often tells a lot

about how useful a soil is for growing crops.

B. Dark brown or black topsoil is nitrogen rich and high in organic matter. (Indicative of fertile soil)

C. Gray, bright yellow, or red top soils are low in organic matter and need nitrogen enrichments to support most crops.

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To support a good crop, the soil must have the following:

1. Have a good supply of nutrients and a good nutrient holding capacity.

2. Allow infiltration, have a good water-holding capacity, and resist evaporative water loss.

3. Have a porous structure that permits good aeration.

4. Have a pH near neutral (pH 7)5. Have a low salt content.

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Soil Degradation

A. When key soil attributes required for plant growth or soil ecosystem services deteriorate over time, the soil is considered degraded.

B. How is topsoil lost? The most pervasive and damaging force is erosion, the process of soil and humus being picked up and carried away by water or wind.

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Soil Degradation C. Farming, logging, construction,

overgrazing by livestock, off-road vehicles, deliberate burning of vegetation, and other activities that destroy plant cover leave soil vulnerable to erosion.

D. Such human activities can speed up erosion and destroy in a few decades what nature took hundreds and thousands of years to produce.

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Soil ErosionA. Most soil erosion is caused by moving

water.B. Three types of water erosion:

1. Sheet Erosion: occurs when surface water moves down a slope or across a field in a wide flow and peels off fairly uniform sheets or layers of soils. 2. Rill Erosion: the surface water forms fast-flowing little rivulets that cut small channels in the soil.3. Gully Erosion: Rivulets of fast-flowing water join together and with each succeeding rain cut the channels wider and deeper until the become ditches or gullies.

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The five golden rules for soil conservationA. Keep the soil covered.B. Using minimal or no tillage.C. Use mulch to provide nutrients for

crops (not fertilizers)D. Maximizing biomass production.E. Maximizing biodiversity.

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Evaluating Ecosystem Services (ES)

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Soil Profiles in Various Ecosystems

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What do you think?

A. How do the soil profiles in plowed farmland differ from those of unplowed natural areas?

B. What properties of soils change by the act of plowing, both in the short term and in the long term?

The Rock Cycle

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The Rock Cycle

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Make Sure You Clearly Understand:A. Soil and Soil Dynamics

(Rock cycle; formation; composition; physical and chemical properties; main soil types; erosion and other soil problems; soil conservation)

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