Download WHAT DOES SOIL BIOLOGY MEAN TO SOIL QUALITY?

THE
LIVING
SOIL
Functions of soil
Support plant growth
Regulate water flow
Absorb and transform pollutants
Habitat for living organisms

Soil Quality
Objective:
Soil organisms:
• Who are they and what do
they do?
• How do they contribute to soil
quality?
VEGETATION
• Vegetation - Additon of
Organic Matter (OM).
• Prairie ~ OM added to
upper 2 ft. of soil due
to fibrous root system
of grass plants.
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VEGETATION
• Forest ~ OM added to upper 4 “ due to
yearly leaf fall to surface of soil.
Prairie - Border Biotic Factor
• Prairie - Border soils (oak savannahs) have the
influence of the prairie and forest ~ due to
changes in vegetation over the past 8000 years
the soils have been both under prairie and forest.
Organism
Length
Abundance
Soil Organisms:
sizesorand abundances
(diameter) mm (arable systems)
Bacteria
(0.001) 3,000,000,000 / g
Fungi
(0.005-0.020)
50 meters / g
Protozoa
0.010-0.200
100,000 / g
Nematodes
1-4.5
7,000,000 / m2
Earthworms
20-200
950 / m2
Potworms
10-50
65,000 / m2
Isopods
3-18
??
Centipedes
5-80
??
Millipedes
5-50
??
Symphylans
2-15
4,500 / m2
Pauropods
0.5-1.5
5,000 / m2
Diplurans
2-7
30 / m2
Proturans
0.4-2
1,000 / m2
Springtails
1-7
100,000 / m2
Mites
0.1-3
250,000 / m2
Size classification
of soil fauna
• Microfauna (<0.1mm diameter)
–Occupy water films and
existing water-filled pores
• Protozoa, nematodes
• Mesofauna (0.1 – 2mm
diameter)
–Occupy existing water- and
air-filled pore spaces
–Able to break free from
surface tension of soil water
• Potworms, microarthropods
Macrofauna (2-20mm diameter)
–Able to alter soil structure
• Earthworms,
macroarthropods
Bacteria
• Microscopic,
single-celled
• Up to 3 billion/g
• Autotrophs,
decomposers,
plant symbionts,
pathogens
Fungi
•Thread-like hyphae; some form visible
fruiting bodies (mushrooms, bracket
fungi)
• Up to 50
meters/g
• Decomposers,
plant
symbionts,
pathogens,
predators
Protozoa
• Single-celled
animals
• 10,000 100,000/g
• Feed on
bacteria, fungi,
decaying
organic matter,
other protozoa
Nematodes
• 1 - 4.5 mm
• Up to 7 million
/m2
• Bacteria
feeders, fungus
feeders,
predators, plant
roots, parasites
Isopods
• Crustaceans
• Feed on decaying plant residues
Myriapods
• Centipedes – predators
• Millipedes – decaying plant residues
• Symphylans, pauropods
Springtails
• 1 - 7 mm
• Up to
100,000/m2
• Fungus
feeders,
decaying OM,
some plant
feeders
Mites
• 0.1 - 3mm
• Up to
250,000/m2
• Decomposers,
predators,
parasites,
plant feeders
Earthworms
• 2 - 20 cm
• 10 - 950/m2
• Many introduced
species
• Decaying organic
matter
• Different
ecological types
Anecic Earthworms
• Medium to large size
• Dorsal, anterior pigment
• Permanent vertical
burrows
• Forage for plant
residues on the soil
surface
• e.g. Lumbricus terrestris
Endogeic Earthworms
• Small to medium size
• Unpigmented
• Horizontal burrows
in topsoil
• Feed on dead plant
roots and other
buried organic matter
• e.g. Octolasion
tyrtaeum
Epigeic
Earthworms
• Small in size
• Red-brown pigment
• Weak burrowers; do not inhabit
mineral soils
• Forest litter, compost
• e.g. Eisenia fetida
Role in Soil Processes
• Soil formation and soil
structuring
• Nutrient recycling and retention
• Population regulation
Role in Soil Formation
 Fragment and humify organic
residues and mix into mineral soil
Soil formation
Formation and stabilization
of aggregates
Formation of pore spaces
Nutrient Availability
• Symbiotic associations
–Rhizobium and legumes
–Mycorrhizae and most plants
Nutrient Availability
• Nutrient mineralization from
organic matter pools
• Biological nutrient pool
Live weight of soil organisms in annual
cropping systems. These are maximum
recorded weights and estimates.
Bacteria
Fungi
Protozoa
Nematodes
Earthworms
Potworms
Other invertebrates
Total weight:
Kg per hectare
3,500
1,750
175
75
1,100
400
<10
6,000 – 7,000 kg/ha
Population regulation