Soil Origin and Development
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Transcript of Soil Origin and Development
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.