Soil Structure

Soil structure refers to planes of weakness that develop as a soil undergoes changes. Individual particles of sand, silt, and clay are grouped together to find larger aggregates.
For contest purposes, select the most dominant structure in the requested horizon.

GRANULAR

These aggregates are roughly spherical. Granular structure is commonly found in less disturbed or compacted A horizons, generally with higher organic matter. The photo example is from a pasture in Northwest Iowa.

BLOCKY

Common in B horizons, these blocks may have angular or rounded corners. Most common in B horizons or compacted or tilled A horizons.

PRISMATIC

These structures are significantly taller than they are wide. Well-developed B horizons can be one place to find these structures, but may occasionally occur elsewhere.

PLATY

These structures are commonly found in E horizons. These units are significantly wider than they are tall. In some cases, a compacted surface soil will appear to have plates. While these are not formed in the traditional manner, students may have difficulty distinguishing the two, so we will include that compaction structure within platy.

STRUCTURELESS

In these areas, the soil does not have structure significantly different from when it was deposited. You should select one of the following options:

MASSIVE

While materials can stick together, soil breaks where pressure is applied instead of pre-formed planes of weakness.

SINGLE GRAINED

Individual sand grains, lacking the fine materials to stick together. These structures are found in sandy materials where it is not possible to remove large aggregates of soil profile without them falling apart as in a sandbox.