Chapter 13 Soil and Its Uses

Soil Science

The study of soil as a natural resource on the surface of the Earth.

Soil formation; classification and mapping; physical, chemical, biological, and fertility properties of soils; and these properties in relation to the use and management of soils.

What are the 4 major principles in soil science?

Sediment, which is formed as a result of Geologic Processes.

What is a major component of soil?

Pedology

The scientific study of soils.

1862; Friedrich Fallou

When was the term pedology coined and by who?

The surface is dynamic or always changing.

If Earth is not static or unchanging, then what is it?

Crust

The thin, outer, solid surface of the Earth that covers the underlying mantle.

Mantle

A layer that makes up the majority of the Earth that and surrounds small core of iron.

Core

The center of the Earth that consists primarily of iron and nickel and has a solid center and a liquid outer region.

Lithosphere

A combination of the crust and solid outer layer of the mantel that forms the plates that move over the Earth's surface.

Asthenosphere

The thin layer below the Earth's outer mantle capable of plastic flow.

Theory of Plate Techtonics

The concept that the outer surface of the Earth consists of large irregularly shaped plates composed of rigid lithosphere and that these plates are slowly moving over the surface of the weaker, plastic asthenosphere.

Processes that create and destroy the Earth's crust.

What processes do plate tectonics involve?

Rifting, colliding, or lateral motion.

What three ways do plates interact?

Divergent Plate Boundary

A plate boundary in which new oceanic crust and lithosphere is created (mid oceanic ridges or rift valleys) in the process of Sea Floor Spreading as two or more parts pull away from each other.

Convergent Plate Boundary

A plate boundary in which two plates are moving toward each other, and marked by volcanic eruptions, large mountains, deep sea trenches, and earthquakes.

Transform Plate Boundary

A plate boundary in which two plates grind past each other resulting in faults such as the San Andreas Fault. Earthquakes often occur at fault lines. The lithosphere is neither created or destroyed. Location of large Earthquakes.

Plate techtonics

Explains how the surface of the Earth is constantly being recycled, created, and destroyed. All rock formation is related to Plate Tectonic activity.

Weathering and Erosion

What are two Geologic Processes that act on the Earth's surface as a result of interaction between the surface and the climate system and are the first steps in the soil formation process?

Weathering

The physical and chemical breakdown of material; involved in the breakdown of parent material in soil formation. This process is important in reducing the size of particles that can then be dislodged by moving water and air.

Mechanic Weathering

Physical forces that reduce the size of rock particles without changing the chemical nature of the rock.

The changes in temperature that tend to result in fractures in rock, the freezing of water into ice that expands and tends to split larger pieces of rock into smaller ones, and the actions of plants and animals.

List 3 common causes of mechanical weathering.

Abrasion

Forces that move and rub rock particles against each other and aid in the physical breakdown of rock.

Chemical Weathering

Involves the chemical alteration of the rock in such a manner that it is more likely to fragment or to be dissolved.

Hydrolysis

A process in which kinds of rock may combine with water molecules.

Erosion

The processes that loosens, wears away, and moves particles from one place to another by wind, water, and ice.

1941; Hans Jennys

The paradigm of soil science was formulated when and by who?

1876; Vasili Dokuchaev

The fundamentals of soil investigation was formulated when and by who?

18th Century

Scientists began to study the soils in which century?

Land

The surface of the Earth not covered by the oceans.

Soil

A thin covering over the land consisting of a mixture of minerals, organic material, living organisms, air, and water that together support the growth of plant life.

45% mineral, 25% air, 25% water, and 5% organic matter.

What percentages of mineral, air, water, and organic matter make up "good" agricultural soil?

Depending on how and when they were formed.

How do soils and their horizons differ from one another?

Geological and biological

Soil formation is a combination of what two processes?

Parent material, climate, topography, biological factors, and time.

List the 5 soil forming factors.

Glacial Till

Material ground up and moved by glaciers.

Parent Material

The material that is weathered to become the mineral part of the soil.

Temperature and moisture amounts cause different patterns of weathering and leaching; wind redistributes sand and other particles; the amount, intensity, timing, and kind of precipitation influence soil formation; seasonal and daily changes in temperature affect moisture effectiveness, biological activity, rates of chemical reactions, and kinds of vegetation.

List 4 ways that climate affects soil formation?

Slope and aspect affect the moisture and temperature of soil.

How does topography affect soil formation?

Plants, animals, microorganisms, and humans.

List 4 biological factors that affect soil formation.

Over time soils exhibit features that reflect the other forming factors and longer time leads to more well developed soils.

How does time affect soil formation?

Humus

The organic material resulting from the decay of plant and animal remains. It is a very important soil component that accumulates on the surface and ultimately becomes mixed with the top layers of mineral particles.

Earthworms, nematodes, mites, pill bugs, and tiny insects.

List some small soil animals that help to incorporate organic matter into soil.

By collecting dead organic material from the surface and transporting it into burrows and tunnels. When the roots of plants die and decay, they release organic matter and nutrients into the soil and provide channels for water and air.

How do small soil animals help to incorporate organic matter into the soil?

Dry or cold climates develop soils very slowly because they have slow rates of accumulation of organic matter needed to form soil.

What is the relationship between climate and time in dry or cold areas?

Humid and warm climates develop soils more rapidly.

What is the relationship between climate and time in humid and warm areas?

It influences the availability of nutrients, which affects the kinds of plants that will grow, which affects the amount of organic matter added to the soil.

Why is soil pH so important?

Basic characteristics, such as color and particle size.

When and how soils are formed determines what?

Thinner

Compared to soils on the bottom land, soils formed on a steep slope that is facing the sun will be what?

Climate, topography and parent minerals.

List 3 environmental conditions that can affect the health of the soil ecosystem.

An increase in the amount of nutrients in the soil.

When burrow animals, such as the earthworm, eats its way through soil, what is the result?

A few years.

How long does it take for soil in cold dry climates, under good conditions, to form?

Rainfall and Temperature

What 2 aspects of climate influence the development of soil?

Soil texture, structure, atmosphere, moisture, biotic content, and chemical composition.

List the 6 properties of soil.

Soil Texture

Is determined by the size of the mineral particles within the soil. Sandy soil has large particles and clay soil has small particles.

Ability of soils to hold and allow water to percolate through.

What does soil texture affect?

Loam

A soil type with good drainage and good texture that is ideal for growing crops.

Soil Structure

Refers to the way various soil particles clump together. Sand has little structure because the particles do not stick to one another.

Friable

A soil characteristic that describes how well a soil crumbles.

Protozoa, nematodes, earthworms, insects, algae, bacteria, and fungi.

List 7 typical inhabitants of soil.

Air, water, and biotic content.

What three aspects of soil structure control biotic activity?

The proportion of sand, clay, and silt.

Soil texture is determined by what 3 things?

Soil Profile

A series of horizontal layers in the soil that differ in chemical composition, physical properties, particle size, and amount of organic matter.

Horizon

A horizontal layer in the soil

A Horizon

A topsoil that consists of small mineral particles mixed with organic matter. Because of the relatively high organic content, it is dark in color.

Litter

A layer of undecomposed or partially decomposed organic matter on the soil surface.

Leaching

The movement of minerals from the top layer of soil to the B horizon by the downward movement of soil water.

E Horizon

A lighter-colored layer that develops below the A horizon that usually contains few nutrients because water flowing down through the soil dissolves and transports nutrients to the underlying B horizon.

B Horizon

Often called the subsoil, contains less organic material and fewer organisms than the A horizon. However, it contains accumulations of nutrients that were leached from higher levels. Often, clay minerals that are leached from the topsoil are deposited in this layer.

A dark colored with much organic matter mixed with mineral matter that has maximum biological activity.

Describe the A Horizon.

Remove of materials dissolved or suspended in water occurs here.

Describe the E Horizon.

Maximum accumulation of silicate clay minerals or iron and organic matter.

Describe the B Horizon.

The area below the subsoil with a horizon of weathered parent material.

Describe the C Horizon.

Bedrock

Describe the R Horizon.

Grassland, forest, and desert soils.

There are thousands of different soil types, but many of them can be classified into three broad categories that are what?

Soils formed in the grasslands have a deep A horizon, and the shallow B horizon does not have sufficient nutrients to support root growth.

Describe grassland soils.

Soils formed in forests have a thinner A horizon, and leaching transfers many nutrients to the B horizon. Thus, roots are found in both the A and B horizons.

Describe forest soils.

Soils formed in the desert have very poorly developed horizons. Since there is little rainfall, deserts do not support a large amount of plant growth, and much of the soil is exposed.

Describe desert soils.

Tropical Laterite Soils

Because nutrients are quickly removed, these

soils are very infertile, and erode easily when vegetation is removed. When these areas are

cleared, the crops that are usually grown do

not do well due to low nutrient content, and land is quickly abandoned.

Has abundant organic material and consists of the O and the A horizons.

List some characteristics of topsoil.

Also called the B horizon which is sticky, cohesive, and rich in clays.

List some characters of subsoil.

Vegetation, amount of rainfall, and topography.

List 3 things that affect soil profiles.

Desertification, deforestation, flooding, and farming.

List 4 things that can deplete soils.

The Emergency Farm Mortgage Act, The Farm Bankruptcy Act, The Drought Relief Service, The Resettlement Administration, and the Soil Conservation Service.

During the 1930s, in response to catastrophic soil erosion, the U.S. government responded with a comprehensive package of measures, both to give short-term economic relief and provide for long-term agricultural research and development. Examples of these initiatives include:

The Emergency Farm Mortgage Act

Prevented farm closures by helping farmers who could not pay their mortgages.

The Farm Bankruptcy Act

Restricted banks from dispossessing farmers in times of crisis.

The Drought Relief Service

Would buy cattle in emergency areas at reasonable prices.

The Resettlement Administration

Would buy land that could be set aside from agriculture.

Soil Conservation Service

This was created within the Department of Agriculture to develop and implement new soil conservation programs, and also undertook a national soil survey.

Soil structure, texture, drainage, fertility, rockiness, slope of the land, amount and nature of rainfall, and other climatic conditions.

The kinds of agricultural activities that land can be used for are determined by what 8 conditions?

First, a dirty stream is less aesthetically pleasing than a clear stream. Second, too much sediment in a stream affects the fish population by reducing visibility, covering spawning sites, and clogging the gills of the fish. Third, the soil carried by a river is eventually deposited somewhere else.

List 3 undesirable effects that result from the movement of excessive amounts of soil from farmland into streams.

Enhance organic matter, avoid excessive tillage, manage pests and nutrients efficiently, prevent soil compaction, keep the ground covered, and diversify cropping systems.

What are the 6 soil quality management components?

Contour Plowing (Contour Farming)

A method of tilling at right angles to the slope of the land that is one of the simplest methods for preventing soil erosion.

Strip Farming

The planting of crops in strips that alternate with other crops in order to reduce soil erosion.

Terraces

Level areas constructed at right angles to the slope to retain water and greatly reduce the amount of soil erosion. On very steep land, this is the only practical method of preventing soil erosion.

Gasoline powered landscape equipment, residential application of pesticides, yard wastes, and lack of lawn water absorption.

Traditional landscaping and current landscape maintenance practices, while frequently meeting human needs and aesthetics, often have harmful environmental impacts. These impacts include:

Provides habitat for local and migratory animals, conserves native plants, and improves water quality.

Natural or native landscaping attempts to balance our needs and aesthetics with those of the environment. What are 3 benefits of this?

Norway maples, kudzu, purple loosestrife, and multiflora rose.

What are some examples of invasive exotic plants?

Waterways

Depressions on sloping land where water collects and flows off the land.

Windbreaks

Plantings of trees or other plants that protect bare soil from the full force of the wind and reduce the velocity of the wind, thereby decreasing the amount of soil that it can carry away.