2. Soil Fundamentals

2.1 Physical Characteristics

Soil physical characteristics often dictate the success or failure of an agricultural project. If you do not work within the physical characteristics of the soil, you will find yourself fighting an uphill battle. Management practices can help improve desirable soil physical characteristics, such as robust soil structure and ideal bulk densities, but they can also have negative impacts on a soil’s profile, such as creating a restrictive layer that prevents water movement. Lastly, management practices are unable to change inherent physical characteristics, such as texture; it is always necessary to work with rather than against inherent characteristics to ensure soil health improvements and the success of agricultural operations.

Soil physical characteristics are often likened to the building materials of a house, which are put together to form its walls and rooms, and overall architectural structure. Analogously, soil physical characteristics form “soil architecture.”

Brady & Weil, 2010

Soil texture and structure together give soil its ability to convey water and air, hold soil nutrients, and provide the space in which soil chemistry and soil biology occur.

Learning Outcomes

After completing this section you will be able to:

• Distinguish which soil characteristics can and cannot change, based on management of a given area within a given amount of time

• Describe the processes by which soil is formed and lost

• Describe how soil texture, structure, and bulk density affect soil functions

• Determine texture by settlement and by the feel method

• Determine soil bulk density

• Compare water stable aggregates from different soil types and management regimes

• Describe what impacts soil organic matter has on soil structure

• Describe how water is held and flows within a soil and with respect to plant availability