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Texture
• Sand– Largest particle size:
0.05 – 2.0 µm
• Silt– Middle particle size:
0.002 – 0.05 µm
• Clay– Smallest particle size:
< 0.002 µm
Texture
• Drives moisture holding capacity– Clay holds most water
– Sand holds least water
• Factor in ease of erosion– Sands are most easily
erodedhttp://www.dahlias.net/dahwebpg/Soil/Soil_07.htm
Structure
• How closely bound soil particles are– Aggregate
• Different shapes allow for different density of compaction– Ex. Platy structure
packs more particles than blocky
http://www.soils.agri.umn.edu/academics/classes/soil2125/doc/s3chap1.htm
Structure
• Soil structure is important for root penetration nutrient retention
• Influences erodibility
Profile
• How soil stratifies over time
• Different for different plant communities
• MULL– Forms under
hardwoods
• MOR– Forms under conifers
Bulk Density
• The mass of soil per unit volume– Kg/m3
• As compaction occurs bulk density increases– More soil in the same
area
• High bulk density makes rooting harder
Temperature
• Important for optimum root growth & aerobic/anaerobic processes
• A factor of moisture and aeration
• As temperature increases, so does respiration
Porosity
• The total volume of space in a given volume of soil occupied by air or water
• Air space between soil particles = “pore space” http://www.mmm-tech.de/data/pix/bodenquer_en.jpg
Fertility
• Fertility depends on nutrient status– Soils require specific ratios of nutrients – Key nutrients for fertility are N, P & K
• If soil is impaired by acid deposition:– Use soil amendments such as Ca or Mg which
can raise soil pH
Soil Water
• Water retained within soil pores
• Depends on soil:– Texture
– Porosity
– Bulk density
• Contains nutrients for plant intake
Leaching & Weathering
• How nutrients are added and removed from the soil over time
• Soil parent material inputs nutrients through weathering– When inputs decrease
= stress or pollution present
Soil Organic Matter
• Made up of decomposed organic material– Important for moisture
retention– Nutrients for plants
• C:N ratio– As C increases, N is
depleted by decomposers
Microflora
• Bacteria:– Rhizobium
• Fix nitrogen
– Azotobacter• Members of the
rhizobium family
– Nitrosumonus
Ectomycorrhizae
• Provides pathogen resistance– Pinaceae
• Pine, Spruce, Firs
– Fagaceae • Beech, Oak