Soil--LithosphereMrs. B-Z

Soil--definition

Complex mixture of eroded rock, mineral nutrients, decaying organic matter, water, air, and billions of living organisms

Indirect resources from soil Provides us with wood, paper,

fiber, and medicines

Direct benefits of soil

Purifies water Decomposes biodegradable

waste

We Study Soil Because It’s A(n)

Great integrator

Producer andabsorber of gases (CO2 and others)

Medium for plant growth

Medium of crop production

Home to organisms(plants, animals and others)

Waste decomposer

Snapshot of geologic, climatic, biological, and human history

Source material for construction, medicine, art, etc.

Filter of water and wastes

Essential natural resource

Medium of heat andwater storage

Hydrologic Cycle and the Soil

Color

Structure

Bulk Density

Texture

pH

Temperature

Moisture

HorizonDepths

Soil Properties that are part of the hydrologic cycle.

Soil Forming Factors

Parent Material

Topography

(The first four factors over) Time

Climate

Biota

These five factors work together to create a unique soil profile made of layers called horizons.

Soil Characterization

Ways to Describe soil:•Zones or Layers of Soil

•Material contained in Soil•Soil Texture

•Soil Structure •Soil Color

•Soil Permeability•Soil pH

Soil horizons

Zones of mature soil layers

Finding and Describing HorizonsSoil Pit Technique

Arid climate soil in New Mexico, USA

Forest soil in Florida, USA

First, obtain permission to dig a pit. Obey any and all safety precautions requested, and ask about power and water lines.

Soil profile

Cross sectional view of the horizons

Forest soil in Florida, USA Forest soil in Tallinn, Estonia

Soil profiles in different geographic regions will be similar if the five soil forming factors act on those soils in the same way.

Soil Profile Comparison

Humus

Partially decomposed matter found in top soil

Organic layer

A horizon

Top-most layer Top soil

B-horizon

Subsoil Soil’s inorganic material

broken down Clay, sand, silt, and gravel

C horizon

Parent material Usually bedrock or some type

of rock

Soil texture

Determined by different sizes and types of minerals

Horizon PropertiesSoil Texture (continued)

To Determine Soil Texture

loams

Soils with roughly equal amount of clay, sand, silt, and humus

Horizon PropertiesSoil Texture (continued)

To Determine Soil Texture

Soil structure

How particles are organized and clumped together

Horizon Properties

With StructureGranular Blocky

Prismatic

Columnar

Platy

Soil Structure

Single Grained Massive

Horizon PropertiesSoil Structure (continued)

Without Structure

Pencil is 19 cm

See hands for relative size

Soil porosity

Measure of the volume of pores or spaces per volume of soil and average difference between spaces

Soil permeability

Average size of spaces or pores

Horizon Properties

Soil Color

Munsell Notation

Hue Value Chroma

Horizon Properties

Soil Color (continued)1

2

3

4

Horizon PropertiesSoil Consistence

Loose*

Extremely FirmFirm

Friable

* Soils with “single grained” structure always have loose consistence.

Horizon PropertiesSoil Texture

Relative Size Comparison of Soil Particles

barrel

plate

Sand (feels gritty)

Silt(feels floury)

coin

Clay(feels sticky)

(2.00 - 0.05 mm, USDA)

(2.00 - 0.02 mm, ISSS)

(0.05 - 0.002 mm, USDA)

(0.02 - 0.002 mm, ISSS)

(< 0.002 mm, USDA)

(< 0.002 mm, ISSS)

Horizon PropertiesTest For Free Carbonates

This is strong effervescence.

Infiltration

Downward movement of water through soil

leaching

Water dissolves materials in the upper layers and the solution is carried to the lower areas

pH

Acidity or alkalinity in water solutions

Environmental Problems with Soil Soil ErosionFamine/Hunger

Soil erosion

Movement of soil components especially surface litter and top soil

Caused by Water Wind How much soil is there?

http://soil.gsfc.nasa.gov/app_soil/hmsoil.htm

Problems with erosion

Feed millions more people with billions metric TONS less of top soil each year

75 billion metric tons of soil erodes every year

How long does it take for one inch of top soil to form?

http://soil.gsfc.nasa.gov/inch/soiltime.htm

Soil Conservation

Reducing erosion Restoring fertility

Conservation-tillage farming Disturbing the soil as little as

possible when planting This holds in more moisture as

well.

Contour Farming

Planting crops in rows according to the contour of the land

Strip Cropping Alternating a crop that needs to be

in rows (like corn) with one that does not (like grass).

Windbreaks Long rows of trees are planted to

partially block the wind from eroding the soil

Alley Cropping

Several crops are planted in strips or alleys between trees or shrubs (wind breaks).

Restoring Fertility

Organic Fertilizer—from plant and animal materials

Commercial Fertilizer—produced from minerals

Crop Rotation

Corn, tobacco, and cotton deplete soil nutrients so farmers rotate these from growing in the same plot of land two seasons in a row. The next season a legume will be planted instead like barley, rye, or soybeans.

How is food produced

Industrial Agriculture—uses large amounts of fossil fuels, water, commercial fertilizers and pesticides

How is food produced

Plantations—industrialized in tropical, developing countries (coffee & bananas)

How is food produced

Traditional—enough for yourself and your dependents

More human labor

Green Vegetation

More energy is given off than was used to produce it

Livestock

Three units of energy put into every unit of energy produced.

World Food

Under-nutrition—enough food to survive but not the right food groups

Malnutrition—not enough food to survive

World Food

From 1950-90, food production rose 3x and per capita rose 36%.

88 Developing countries are behind with food for population. But this fell from 36% to 14%.

World Food

It is surprising to note that there really is enough food to feed everyone, but it is not equally distributed.

Protecting Food

Pesticides—chemicals used to kill organisms that are undesirable

Pesticides

Insecticides Herbicides Fungicides Nematocide

s Rodenticide

s

Which uses more pesticides—a lawn or a farm?

Surprisingly a LAWN—A lot more!

Argument for Pesticides Saves human lives (malaria and

bubonic) Increases food supply Lowers cost 55% of food supply is lost 37% of US food is lost Work faster and better than

alternatives Risks are outweighed by benefits

Against pesticides

Genetic resistance Broad spectrum could hurt

unharmful organisms Wiping out natural predators

unleashing new pests previously held in check

Harm wildlife Harm humans

Alternatives to Pesticides Crop rotation Plant crops to draw pests to

them Genetic modification Biological predators Biological pesticides Radiating food

Integrating Pest Management See pests as part of the

ecosystem Find harmony between crops

and pests

Sustainable Agriculture

Combine traditional polyculture and modern monoculture

More perennial crops Minimize soil erosion Reduce deforestation Reduce water waste Reduce overuse of fossil fuels Use organic fertilizers Use biological pesticides