Soils Exam 3

Soil Health

the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans.

• Non-renewable

___ references soil as an infinite, non-renewable, and dynamic living

Soil Quality Indicators

Chemical, Biological, and Physical properties

Soil Quality

_ references the function of a soil to sustain plant and animal productivity, maintain and enhance water and air quality, and support human health

related to soil function.

When would you expect the most environmental loss of nutrients?

Winter-spring

List the three mechanics of water erosion.

Detachment, Transportation, and Deposition

List the three types of water erosion.

Sheet, Rill, and Gully

List the three types of wind erosion.

Saltation, Soil Creep, Creep, suspension

Windbreaks

Tree protects area 10x their height
Grass protects area 5-7x barrier height

Texture, depth, rock fragments, and drainage are considered _ soil properties that we cannot alter or manage. Available water capacity, infiltration, and soil organic carbon are_soil properties that we can alter or manage.

Inherent Dynamic

Which variables in the USLE can we adjust?

C and P

The terminal velocity of a raindrop can reach .

18.5 mph

Biological properties

Earthworms (OM & Respiration)
Microbial biomass C and N
Particulate organic matter
Soil enzymes, soil respiration, and total organic carbon

Soil Properties - Inherent

cannot be altered by use and management
Texture, depth, rock fragments

Soil Properties - Dynamic

can be altered by use and management
Available water capacity, infiltration, structure of surface layer, soil organic C

Soil Properties

Texture
Structure
OM
Porosity
Bulk Density

Primary causes of Land Degradation / Soil Erosion

Overgrazing, Deforestation, Ag activities, Over exploitation, Industrialization

Geological Erosion

natural soil erosion

Accelerated Erosion

10x - 1000x > geographical erosion

What is the greatest polluten of waterways?

Sediment

USLE

A= RK(LS)CP

R= rainfall erosivity
K= soil erodibility
LS= Slope length & steepness
C= cover & management
P= erosion control practices

Soil Erodibility (K Value)

High K values (more erosion)
Low K values (Less erosion)

To be considered conservation tillage, at least _ of the soil surface must be covered with residues.

30%

Conservation Tillage

No-Till
Ridge Till
Strip till
Mulch /till
Reduced till

Contour cropping

slows the flow of water- more effective if planted on ridges

strip cropping

water cannot build up velocity

• similar to shortening slope length

Bench Terraces

used where control of runoff must be achieved- rice paddies

Broad-based terraces

water gently flows in a terrace channel to a grassed waterway

Wind Erosion

Same mechanics as water erosion

• Detachment, Transportation, Deposition

Movements, Salation (>50%), Soil Creep (5-25%), Suspension (50%)

Factors Affecting Wind Erosion

Velocity, Turbulence, Surface roughness, Soil Properties, Vegetation

Minimizing Wind Erosion

soil moisture
tillage
barriers

List 4 factors that influence OM decomposition and mineralization.

Environmental conditions
Quality of Residues
Physical Factors
C:N Ratio

What are the two basic processes of the Carbon cycle?

Photosynthesis
Decomposition

Order the following organic compounds in order from fastest to slowest decomposition. 1 = fastest, 6 = slowest

1. Sugars, starches, simple proteins
2. Crude proteins
3. Hemicellulose
4. Cellulose
5. Fats, waxes, oils
6. Lignin, phenolic compounds

Which of the three humic substances discussed in class is the most resistant to microbial attack?

Humin

Plant residues are composed of% water and_% dry matter.

75%, 25%

List the complete names for the 3 humic substances discussed in class.

fulvic acid

humic acid

humin

One can expect decomposition to be rapid under _ conditions and slower under _ conditions.

aerobic

anaerobic

organisms require a specific environment, either aerobic or anaerobic, to survive.

Obligate

Which of the soil microorganisms discussed in class break down simple compounds like sugars?

Bacteria

Which of the soil microorganisms discussed in class break down complex compounds like cellulose?

Fungi

_ receive their C from CO2. _ receive their C from consuming organic food sources.

Autotrophs

heterotrophs

__ is the study of an organism in relation to its environment.

Ecology

Organic Components of a soil

• fresh residues
• decomposing OM
• stable OM
• living organisms

Soil C > plant & atmospheric C

Active Fraction of SOM

-10 - 30% responsible for maintaining soil microorganisma
-High C:N ratio (15:1 to 30:1)
-Most susceptible to soil mgnt practices

Passive & Slow Fractions

-Very Stable (1000's yrs)
-60-90% to soil OM
-CEC and H2O holding capacity

Composition of plant residues

75% H2O, 25% Dry Matters

Aerobic

Process that requires oxygen

Anaerobic decomposition much slower

Methane or alcohol byproduct
greenhouse gases

Autochthonous

digest very resistant & stable SOM
Low activity organisms - fungi

Zymogenous

• active when readily decomposable organic materials added to soil
• cellulose decomposing organisms
• high activity (bacteria and actinomycetes)

Soil Organic Matter

Biomass, Debris, Humus

Vermicomposting

the use of earthworms to convert organic waste into fertilizer.

Benefits of Compost

C:N Ratio = 14:1 to 20:1
Avoid N Competition (immobilization)
N Stabilization
Safe storage
Easier Handling
Partical sterilization
Detoxification
Disease Supression

Corn-oats-clover

greatest SOM vs. continuous corn

Minimize N losses

leaching
runoff
volatization

Important activities of soil organisms

Physical mixing of soil
Decomposition of plant & animal residues, formation of humus
N2 - fixation
Economic losses - Plant diseases & nematodes
Degradation of pesticides, petroleum products
waste disposal/ degradation
sewage treatment, septic tanks, & animal wastes

Ecology

Study of organisms in relation to its environment

Ecosystem

Self-sustaining community of organisms & their environment

Photosynthetic organisms are

Primary Producers

Detritus

Plant and animal remains "parent material" for soil OM

Soil Fauna

Animals, heterotrophs

Soil microflora

microbes, 'microbial bio mass'

Soil humus

serves as a storehouse of nutrients for plants, animals, and microbes

Facultive

organisms capable of either type of respiration

Autotrophs

C from CO2

photoautotrophs

energy fromlight

chemoautotrophs

energy from chemical reactions

heterotrophs

require organic food sources, C from organic compounds

Soil Biomass

the total mass of living organisms in the soil

abiotic- moisture ans temp
biotic- predation and competition
soil chemical properties - acidity, dissolved nutrients, and salinity

Algae

primary photoautotrophs

Lichens - symobiotic relationship w/ fungi, N2 -fixation- physical support, also cranobacteria

Fungi

Heterotrophs - mostly aerobic, some tolerate low O2
Decompose cellulose, starch, gums, waxes, and ligin

3 types:
yeasts - fermentation
molds
mushrooms -breakdown of woody tissue

Mycorrhizae

A symbiosis with plant roots and fungus

Ectomychorrhiza - from a fungal mantle around roots, infection b/w outer roots cells

Endomycorrhiza - Infect cortical cells with branch of hyphae throughout soil

Bacteria

Most are Heterotrophs
Important decomposers - sugars & protiens

Factors Influencing Microbial Growth

Organic substrates
*Bacteria - simple compounds (sugars, starches, & protiens)
*Fungi - complex compounds (cellulose)
Oxygen Requirement
Soil Moisture & Temp
Soil pH

Microfauna

Nematodes - unsegmented microscopic worms
Protozoa - singled celled animals

Macrofauna

Arthropods - Exoskeleton, segmented bodies, pair of joined parts, insects, spiders, centipedes, millipedes, crustaceans, invertebrates
Mollusks - gastropods (belly-footed)
Vertebrates

Fertilizer Analysis

Biomass * %N * 0.5 = PAN

Rate/Analysis= lb/ac

$/ton = $/lb