Soil Biology and Organic Matter

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Soil Biology and Organic
Matter
I. Overview
A. Soil is…..
•
Minerals (the body)
•
Organisms (the life)
Vital to soil formation and development
I. Overview
A. Soil is…..
•
Minerals (the body)
•
Organisms (the life)
Vital to soil formation and development
B. Teems with life
• 1 million bacterial in each cubic cm of topsoil
• 1 million earthworms per acre
• More Biomass beneath our feet than above
II. Plants (Macro and Micro)
III. Animals (Macro and Micro)
II. Plants
A. Microflora
Why important?
II. Plants
A. Microflora
Why important?
•
Most crucial life forms in soils (by far, the most
abundant in number)
II. Plants
A. Microflora
Why important?
•
•
•
Most crucial life forms in soils
They generate their energy by breaking down
complex organic tissue, thereby freeing vital
nutrients for other plants.
(Without these critters, these nutrients could
be locked up indefinitely in complex organic
compounds)
II. Plants
A. Microflora
• Bacteria
Single celled organisms;
Greater number of organisms present than all others combined
II. Plants
A. Microflora
• Bacteria
o
Heterotrophic – derive energy by consuming
complex organic debris (leaves, roots, stems,
animal tissue)—releases ammonium for plants
Requiring organic compounds of nitrogen and oxygen for nourishment
Rhizobium Bacteria—fix Nitrogen from air (Legumes)
II. Plants
A. Microflora
• Bacteria
Heterotrophic – derive energy by consuming
complex organic debris (leaves, roots, stems,
animal tissue)—releases ammonium for plants
o Autotrophic – oxidize inorganic materials
(sulfer, iron, carbon, ammonia).—releases
nitrate and nitrite.
Producing complex organic nutritive compounds from simple inorganic
o
sources by photosynthesis
A. Microflora
• Actinomycetes (Act-tin-o-my-ce-tes)
o Single-celled organisms slightly larger
than bacteria (fine, thread-like)
o Decompose complex organic materials
in later stages in conversion to humus.
o Capable of producing antibiotics
A. Microflora
• Fungi
o Heterotrophic organisms capable of
decomposing highly-resistant and complex
organic compounds.
o Dominant flora when pH is less than 5
also…mycorrhizae fungus (Mi-cor-rizie)
Extension of
Plant roots
A. Microflora
• Algae
Simplest green plant (needs sun and water)
Blue-Green Algae most common
Aids in adding organic matter
Old ham sandwich residue from Geology
Club fridge……
A. Microflora
Factors Limiting Microflora
• Adequate supply of organic matter
• Temperature (Peat Bogs too cool, desert
too hot)
• Moisture
• pH (6-8 optimal—Rizobium bacteria very
sensitive)
• Oxygen Availability (most microflora
aerobic)
Whereas microflora are affected by the
ambient temperature and moisture,
MACROFLORA tend to form in response to
climate, parent material, and slope
conditions.....
II. Plants
B. Macroflora
• Grasses
• Shrubs
• Trees
Function:
• Produce an array of complex organic
materials (leaves, roots, stems, bark,
wood, seeds)—affect soil chemistry,
water retention, pH, organic matter, etc.
Function:
• Produce an array of complex organic
materials (leaves, roots, stems, bark,
wood, seeds)—affect soil chemistry,
water retention, pH, organic matter, etc.
• Aid in rock weathering and soil formation
• Protect soil from erosion
III. Animals
A. Microfauna
Protozoa (amoebae, ciliates, flagellates)
Single-celled organisms, need moisture
(dormant when dry)
“grazers, eat bacteria”—digestion aids
organic decomposition.
III. Animals
A. Microfauna
Nematodes (“eel worms”)
• More complex than protozoa
• Dine on decomposing organic matter,
living soil animals, living plant roots
• Destructive to crops
III. Animals
A. Macrofauna
Ants and Earthworms
Major mixers of soil
Openings allow air and water movement
III. Animals
A. Macrofauna
Springtails, Mites, Mammals, Humans
“mix, mechanically alter
add organics…”
IV. Soil Organic Matter
A. Sources
IV. Soil Organic Matter
A. Sources
• Predominantly from plant tissue
• Animals (minor source)
• Earthworms, centipedes, ants process
and move plant residues
IV. Soil Organic Matter
B. Humus Formation
1. Term used for organic matter which has gone
under extreme decomposition
Great source of N, P, S
Extensive decomposition
Raw Organic
Matter
Humus
IV. Soil Organic Matter
B. Humus Formation
2. The ingredients of humus…
(Humus)
(N Compound)
Proteins—stores and slowly releases N in soil
Also find concentrations of P, S, and high CEC
Ability to absorb large volumes of water
IV. Soil Organic Matter
B. Humus Formation
3. Carbon/Nitrogen relationships
Extensive decomposition
Raw Organic
Matter
Humus
800 Carbons
1 Nitrogen
10 Carbons
1 Nitrogen
Why not use sawdust or raw vegetation?
Why not use sawdust or raw vegetation?
• Raw vegetation invites large microbial
population (they feed on C).
• Compete for N, and make it less available
to higher plant communities.
Why not use sawdust or raw vegetation?
• Raw vegetation invites large microbial
population.
• Compete for N, and make it less available
to higher plant communities.
• Decomposition of organics (CO2 gas), and
many critters die and decompose. Nitrogen
remains.
• N fixed as protein in the microbes is now
available to plants
• Resultant humus is highly enriched in N
relative to the original raw vegetation, and
has a greater surface area (higher CEC)
So…should we add sawdust to a garden?
C:N = 400/1
C:N = 10/1
4. Carbon Cycle
IV. Soil Organic Matter
C. Amount and Distribution
C. Amount and Distribution
1. Influence of Climate and Vegetation
Metric tons of organic matter per ha of 1 meter depth
Wisconsin study of prairie vs. forest
soils.
Practical Implications
• Clear and burn method of
woodlands removes the majority of
organics
• Cropping grasslands reincorporates
organic matter into the system
IV. Soil Organic Matter
C. Composting
1. (Compost)—organic material that has
undergone significant biological
decomposition
IV. Soil Organic Matter
C. Composting
1. (Compost)—organic material that has
undergone significant biological decomposition
2. Benefits:
• Reduces volume of organic wastes by 510x.
• Heat generated during decomposition
kills many disease-causing microbes
• Lowers C:N
• Serves as excellent soil conditioner
3. Methods
V. Soil Fertility
A. Fertilizers
V. Soil Fertility
A. Fertilizers
A. Fertilizers
5 – 10 – 5
N P K
V. Soil Fertility
A. Fertilizers
Nitrogen
Sources: ammonium, nitrate
V. Soil Fertility
A. Fertilizers
Nitrogen
* darker, stronger leaves
V. Soil Fertility
A. Fertilizers
Nitrogen
* darker, stronger leaves
* helps with uptake of other
nutrients
V. Soil Fertility
A. Fertilizers
Phosphorous
Sources: ??
V. Soil Fertility
A. Fertilizers
Phosphorous
* strengthens stems and roots
V. Soil Fertility
A. Fertilizers
Phosphorous
* strengthens stems and roots
* enhances flowering, and seed
production
V. Soil Fertility
A. Fertilizers
Phosphorous
* strengthens stems and roots
* enhances flowering, and seed
production
* increases plant’s resistance to
certain diseases
V. Soil Fertility
A. Fertilizers
Potassium (Potash)
V. Soil Fertility
A. Fertilizers
Potassium (Potash)
* strengthens cell walls and stems
of plants.
V. Soil Fertility
A. Fertilizers
Potassium (Potash)
Sources??
V. Soil Fertility
A. Fertilizers
Potassium (Potash)
* strengthens cell walls and stems
of plants.
* helps in plant respiration and
uptake of other minerals.
V. Soil Fertility
A. Fertilizers
B. Organic Matter
V. Soil Fertility
A. Fertilizers
B. Organic Matter
C. Lime
D. Other Essential Element for Plants
Fe, Cu, Zn Mg, Mn, B, Mo, Cl, S,
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