EPSc 413: Introduction to Soil Science
Spring 2017
Prof. Jeff Catalano
#1 Rule of this course:
Soil is not Dirt!!!!
Soils Dominate the Terrestrial
Landscape
Soil is a Complex
Dynamic System
Rates of Soil Production (Gain) and
Erosion (Loss)
• Average rate of natural soil production:
0.02 mm/yr
• Average rate of soil erosion from land used for
agriculture:
2 mm/yr
Soil as a Natural Resource
Soil Erosion in Central US
1000s yrs
Entisol Mollisol
• Soil formation on fresh material takes 1000s of years
• Soils may be eroded or degraded through poor
agricultural practices
• Many of our current practices amount to “mining” soil
• Once gone, some locations will not produce new soils
under current climate conditions
Question: What 1973 science
fiction movie is about soil
degradation?
Hint: The movie stars Charlton
Heston, and is NOT Planet of the
Apes
Soils were Critical to Human History
• Early civilizations developed in river
valleys with rich, fertile soil
• Collapse of many civilizations is often
connected to soil degradation
– Salinization of soils from irrigation in Severe soil salinization in Central
Mesopotamia California
– Erosion of hillside soils in ancient Greece
– Soil degradation across Roman empire
• Darks ages may represent periods of
time needed to regenerate soil
• Lifetime of our current civilization may
depend on our ability to manage and
sustain our soil*
*Read: Dirt: The Erosion of Civilizations by David Montgomery Severe soil erosion in the
for more thoughts on this topic. piedmont region of South Carolina
Population Growth Requires
Improved Soil Management
• Population is growing faster that the amount of
arable land
• Requires increased crop yields (food produced
per unit area of land) to sustain the population
Images from FAO
EPSc 413: Introduction to Soil Science
MW 10-11:30, Rudolph Hall 203
Instructor: Prof. Jeff Catalano
TA: Xandi Barrett
Textbook: The Nature and Properties of
Soils, 15th ed., by Brady and Weil, 2017
Website: http://epsc413.wustl.edu/
Grading Policy: 30%
Homework: 60% (20% each)
Exams : 10%
Field Trip Report:
Exam Policy: see syllabus
Late Work Policy: see syllabus
Grades: see syllabus
Field Trips: One 1-day trip:
Tyson Research Center on April 1
Introduction to Soils
What are the important roles of
soils on Earth?
Major Roles of Soils
“Soil” vs. “A Soil” vs. “The Soil”
• “Soil” is material composed of minerals, water,
gases, organic substances, and microorganisms
• “A Soil” is a specific, 3-dimension natural body
– Harvest silt loam dominates the Danforth campus
– Menfro silt loam dominates Forest Park
– A collection of silt loams dominate Tyson
• “The Soil” is the collection of individual bodies
that cover the Earth’s surface
Components of Soils
Soils are a Mixture of Minerals, Water,
Air, and Organic Matter
50% Holes 50% Solids
Mineral Constituents of Soil
• Soil minerals show a range of sizes and compositions
• Soil structure depends on proportions and
arrangements of soil particles
Soil Organic Matter (OM)
High OM = Good Structure
Mollisol: Grassland soil Histosol: Wetland soil Low OM = Poor Structure
high in OM at surface composed of OM
Soil Water
• Soil water coats the surfaces of minerals and OM
• Soil water contains many solutes, including many of
the elements need for plant growth: The Soil Solution
• Soil solution pH can vary widely
Soil Water
Soil Gases
Rhizosphere: Root-Soil
Interface
Soil is a Complex
Dynamic System
Soil Horizons and Profiles
Soil Horizons
• Soils display distinct layering
• O Horizon: Partially
decomposed organic matter
(OM)
• A Horizon: Near surface,
mineral soil rich in OM
• E Horizon: Leached layer below
A horizon (sometimes absent)
• B Horizon: Accumulation of
minerals, low in OM
• C Horizon: Weathered parent
material
Formation of Soil
Horizons
• Soil horizons form from the
downward transport of
minerals, solutes, and OM
– Downward movement of OM
forms A horizons
– Downward movement of minerals
forms A, E, and B horizons
• A & E lose minerals
• B accumulates minerals
– Downward movement of salts
forms B horizon
Forest Soils
Plains/Grassland Soils
Volcanic Soils
Young or Disturbed Soils
Old Soils
Dry Soils
Frozen Soils
Organic Soils
Man-Made Soils
Key Points
• Soils are diverse!
• Soils play key roles in supporting ecosystems and
food production
• Soils can be made of mostly mineral matter or
organic matter
– 50% Solids, 50% Holes (Pores) filled with air and water
• A soil is composed of horizons, layers formed by
the downward movement of water and solids