Soil Origin and Development

South Central Agriculture Science Academy

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Mineral Matter

Mineral matter includes rock and mineral fragments

These fragments are classified by size:GravelSandSiltClay

Definitions

Pedology = study of soil formationEluviation = removal of material, such as clay or nutrients from a layer of soil by percolating waterLeaching = when water passes through the soil profile and removes chemical compounds or nutrients from the soil in solution

Visit the text book

How does climate effect how soil is formed? Visit page 98 please to answer the question.

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The Components

Soils have four main components that make up the whole

Minerals, 45%

Organic Matter, 5%

Air, 25%

Water, 25%

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Soil Parts

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Organic Matter

Organic Matter includes things, such as:Plant rootsDecaying leaves and other vegetative partsAnimals:

Microorganisms (i.e., nematodes and fungi)Insects (i.e., larva and worms)Small mammals (i.e., gophers and moles)

Animals that help with O.M.

Visit this site:http://school.discoveryeducation.com/schooladventures/soil/field_guide.html

What are the 7 common groups of creatures found in soil? What are each used for?

What is O.M. ??

1. Is the portion of the soil which includes animal and plant remains at stages of decay–Forest= leaves, dead trees, –Prairies=grass roots and tops–Farmland= crop residue

Chemical Makeup of O.M.

1. Consists of complex carbon-containing compounds2. Long chains are formed and other elements use these to make more organic compounds

Chemical Makeup of O.M

3. The most important compounds are–A. Carbohydrates: simple sugars,

starches, and cellulose–B. Lignins: is 10-30% of plant

tissue, makes plants rigid, resists decay

Chemical Makeup of O.M

–C. Protein•Amino acid chains•Supplies Nitrogen when broken down

Decomposition

1. Micro-organisms digest organic matter2. Releases CO2 and H2O3. Carbohydrates are first to be consumed4. Lignin-becomes humus and slowly broke down

Decomposition

5. Decay Organisms need O2 and microorganisms use O2 to oxidize the different compounds6. 1st breakdown is quick and requires weeks or months

Factors affecting O.M.

1. Vegetation– 2 times as much o.m. on grassland to woodland– O.M. is deeper in prairie soil and is in soil

Factors affecting O.M.

2. Climate– Arid conditions soil has less O.M.– High temperatures decay O.M. more rapidly

Factors affecting O.M.

3. Texture– Fine textured soils hold more organic material

because clay protects hums from decay

Factors affecting O.M

4. Tillage – Prairie will return more than cropping

Functions of O.M.

A. Nutrient and water storage–1. O.M. stores many of the nutrients

used by plants and does it in 2 different ways•Colloids hold water and nutrients•O.M. stores nutrients as part of its own makeup

Functions of O.M.

– 2. Both humus and O.M. absorb water like a sponge, humus can store 6 times its own weight

Functions of O.M.

B. Nutrient Availability– Makes several nutrients more available for plant use

Functions of O.M

C. Soil Aggregation (Mixing)– 1. Heavy clay responds best. Breaks down

particles, aerates, and makes easier to work with

Functions of O.M

D. Prevents Erosion–1. Soils kept supplied with O.M.

have improved structure that improves water infiltration

–2. Stops excessive water runoff–3. Increasing O.M. from 1-3% will

reduce erosion up to 1/3

Functions of O.M.

Undesirable Effects–1. Nitrogen is immobilized or tied up

during the decay process and is unavailable to plants

–2. Certain plant residues are toxic to other plants

Maintaining Soil O.M.

A. It is impractical and not economical to raise O.M. levels significantly but should be a goal to maintain at highest levelsB. Adding fresh organic matter will improve soil the best

Maintaining Soil O.M.

C. Crop Residues– Leave all crop materials possible. Don’t burn

residues, harvest some– Use good fertilizer, healthy plants make more

residue

Maintaining Soil O.M.

D. Green Manure– 1. Turn over alfalfa, clover, sudan grass, will

increase N levels– 2. Increases O.M. levels and fixes more nutrients

Maintaining Soil O.M.

E. Crop Rotation– 1. A rotation between row crops, small grains, and

legumes is better for keeping high O.M.

Maintaining Soil O.M.

F. Organic Matter Additions– 1. Animal Manures, sludge, organic wastes– 2. Industries may provide organic wastes, by

products, meat scraps, etc.

Maintaining Soil O.M.

G. Mulches–1. Not economical in large acres–2. Reduce tillage leaves some

mulch–3. Limits water evaporation, keeps

soil temperature cooler on hot days, and warmer at night

Maintaining Soil O.M.

H. Conservation Tillage–1. Conserves topsoil which is high in

O.M.–2. Crop residue decays slower when

left on top–3. No till soils are high in O.M. in the

top layer

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Air

Soil air is trapped in pores of the soil.

Porosity is a term to define how much open space is available for air and water to be held in the soil.

Air provides oxygen for plant roots.

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Water

Soil water is held by soil particles. This allows the water to be available for plants.Organic matter is attributed to holding more water because it creates pores and may even absorb water like a sponge.

Soil Body

Physical Weathering-– refers to the effects of such climatic factors as

Temperature, water, and wind. One of the most important is frost wedging.

– Chemical Weathering- changes the chemical makeup of rock and breaks it down.

– Hydrolysis- water reacts with minerals to produce new and softer compounds

The Soil Profile

Soil does change over time today Scientist have classified them into four areasThey are:– Addition– Losses– Translocations– Transformations

The Soil Profile

What is Additions?– It is materials such as fallen leaves windblown dust

or chemicals from air pollution may be added to the soil

The Soil Profile

What is Losses?– It is materials that may be lost from the soil as a

result of deep leaching or erosion from the surface.

The Soil Profile

What is Translocation?– It is materials that may be moved within the soil as

with leaching deeper into the soil or being carried upward with evaporating water.

The Soil Profile

What is Transformation?– It is the materials that may be altered in the soil, for

example organic matter decay weathering of the minerals to smaller particles or chemical reactions.

The Soil Profile

Each of these processes will occur at different depths of the soil.For example:– Organic Matter will be at the top or the near the

surface of the soil.

The Soil Profile

What is a soil profile?– It is the vertical section through the soil and

extending into the unwreathered parent materials and exposing all the horizons.

Master Horizons

What is the Master Horizons?– The are A, B and C horizons are known as the

master horizons. They are a part of a system for naming soil horizons in which each layer is identified by a code O, A, E, B, C and R

Horizons

The O Horizon-– Is the organic layer made of wholly or partially

decayed plant material and animal debris . You can normally find this layer in a forest with fallen leaves, branches and other debris.

Horizons

The A Horizon-– It is usually called the topsoil by most farmers. This

is where the organic matter accumulates over time. This layer is very prone to leaching and losing iron and other minerals. The A horizon provides the best environment for the growth of plant roots, microorganisms and other life.

Horizons

The E Horizon-– This is the zone of the greatest leaching of clay,

chemicals and organic matter.

Horizons

The B Horizon-– This is also called the subsoil is often called the zone

of accumulation where chemicals leached out of the A horizon

Horizons

The C Horizon-– lacks the properties of the A and B horizon. It is the

soil layer that is less touched by soil forming processes and is usually the parent material soil

Horizons

The R Horizon-– is the underlying bedrock such as the limestone,

sandstone, and or granite.

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References

Huddleston, J. H., & Kling, G. F. (1996). Manual for judging Oregon soils. Corvallis, OR: Oregon State University.

Parker, R. (2010). Plant and soil science: Fundamentals and applications. Clifton Park, NY: Delmar.