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2. Soil Fundamentals
Soil structure affects how the soil responds
to changing conditions. By understanding
soil structure you can start to understand:
Soil air is an important component of a soil’s physical system because soil organisms and plant roots
need air to live. Broadly, soil air is similar to the well-mixed air in the atmosphere. Earth’s atmosphere
comprises approximately 78% nitrogen, 21% oxygen, and <1% carbon dioxide, hydrogen, neon, and
other gases such as methane and water vapor. Root cells, microbes, and larger animals breathe in
oxygen and breathe out CO
2
, just like you and I. Thus in soil, the amount of oxygen can be slightly
lower, and carbon dioxide can be slightly higher than the well-mixed atmospheric air because air in
soil does not mix rapidly with air in the atmosphere.
Soil Air Component
Soil Structure
Glossary
Soil Structure
the arrangement of soil particles (sand, silt,
and clay) and organic matter into aggregates
of different shapes and sizes.
•
The susceptibility of a soil to
erosion by water and wind
•
Pore size distribution (water
movement and retention)
•
Drought tolerance of soils
•
Soil aeration
•
Soil water holding capacity
•
Root growth and proliferation