Soil Structure : Biogeography

 

Soil Structure

• It is defined by the way individual particles of sand, silt, and clay are assembled.
• Single particles when assembled appear as larger particles. These are called aggregates.

Based on the size and shape of peds, there are different structures. Some of them are

1. Granular and crumb structures are individual particles of sand, silt and clay grouped together in small, nearly spherical grains. Water circulates very easily through such soils. They are commonly found in the A-horizon of the soil profile

2. Blocky and sub angular blocky structures are soil particles that cling together in nearly square or angular blocks having more or less sharp edges. Relatively large blocks indicate that the soil resists penetration and movement of water. They are commonly found in the B-horizon where clay has accumulated;

3. Prismatic soil particles that are formed into vertical prismatic structure. Similar to  columnar structure.

4. Columnar structures are soil particles which have formed into vertical columns or pillars separated by miniature, but definite, vertical cracks. Water circulates with greater difficulty and drainage is poor. They are commonly found in the B-horizon where clay has accumulated;

5. Platy structure is made up of soil particles aggregated in thin plates or sheets piled horizontally on one another. Plates often overlap, greatly impairing water circulation. It is commonly found in forest soils.

Soil structure has an important bearing on ease of cultivation.