Transcript 4. Figure 4.3, 4.4

A
hyphae of mycorrhizal
fungi
root hair
root
interior
mucigel layer
cell on root surface
soil aggregate
water film
larger aggregate
B
air space
Figure 4.3. Close-up view of a plant root: (a) The mucigel layer is shown containing some
bacteria and clay particles on the outside of the root. Also shown is a mycorrhizal fungus sending
out its rootlike hyphae into the soil. (b) Soil aggregates are surrounded by thin films of water.
Plant roots take water and nutrients from these films. Also shown is a larger aggregate made up
of smaller aggregates pressed together and held in place by the root and hyphae
Soil ecology in balance
Healthier soil
Greater biological diversity
• Low disturbance
• Crop rotation
• Practices that reduce • Residue cover
soil compaction
• Building organic
• Direct seeding
matter
• Sufficient soil fertility /
slow nutrient release
• Manure / composts
• Neutral pH
• Permanent planting
• Enhanced moisture conservation
• Cover cropping
• Timely irrigation management
MANAGEMENT PRACTICES INFLUENCE SOIL ECOLOGY
• High disturbance
• Tillage
• Burning
• Steam sterilization
• Fumigants
• Monoculture
• Herbicides
• Overgrazing
• Fungicides
• Insecticides
Changing ecology of system
Imbalance in species
Some groups increasing in number; some groups eliminated
Figure 4.4. Management practices that influence soil life. Modified from Kennedy et al. (2004).