Physical Properties

Soil Structure

Sand, silt and clay particles are the primary mineral building blocks of soil. Soil structure is the combination or arrangement of primary soil particles into aggregates. Using aggregate size, shape and distinctness as the basis for classes, types and grades, respectively, soil structure describes the manner in which soil particles are aggregated.

Aggregate Stability

Soil aggregates are groups of soil particles that bind to each other more strongly than to adjacent particles. Aggregate stability refers to the ability of soil aggregates to resist disintegration when disruptive forces associated with tillage and water or wind erosion are applied. Wet aggregate stability suggests how well a soil can resist raindrop impact and water erosion, while size distribution of dry aggregates can be used to predict resistance to abrasion and wind erosion.

Bulk Density

Bulk density is an indicator of soil compaction. It is calculated as the dry weight of soil divided by its volume. This volume includes the volume of soil particles and the volume of pores among soil particles. Bulk density is typically expressed in g/cm3.

Water Capacity

Available water capacity is the maximum amount of plant available water a soil can provide. It is an indicator of a soil’s ability to retain water and make it sufficiently available for plant use.


Infiltration is the downward entry of water into the soil. The velocity at which water enters the soil is infiltration rate. Infiltration rate is typically expressed in inches per hour. Water from rainfall or irrigation must first enter the soil for it to be of value.


Slaking is the breakdown of large, air-dry soil aggregates (>2-5 mm) into smaller sized microaggregates (<0.25 mm) when they are suddenly immersed in water. Slaking occurs when aggregates are not strong enough to withstand internal stresses caused by rapid water uptake. Internal stresses result from differential swelling of clay particles, trapped and escaping air in soil pores, rapid release of heat during wetting, and the mechanical action of moving water.

News & Events

Update: Garretson, 60-inch corn plot

Update: Garretson, 60-inch corn plot

By Austin Carlson, SD Soil Health Coalition Technician Southeastern South Dakota has been fairly dry throughout the summer, receiving approximately 13.25 inches of precipitation for the year with minimal amounts of rain in the last month. Since the last plot update on...

Soil Health Informational Workshop set for Sept. 9 in Pierpont

Soil Health Informational Workshop set for Sept. 9 in Pierpont

A Soil Health Informational Workshop will be held at 5 p.m. on Sept. 9 in Pierpont, SD. Among other soil health concerns, presenters will discuss the new EQIP signup to help producers and landowners in the Upper James River Basin fight the expansion of saline soils....

Low Stress Livestock Handling Workshops set for September

Low Stress Livestock Handling Workshops set for September

A series of low stress livestock handling workshops presented by Dr. Tom Noffsinger, DVM, has been set for five South Dakota locations in September. Sept. 21 - Sturgis Sept. 22 - Belvidere Sept. 23 - Akaska Sept. 24 - Crooks Sept. 25 - Yankton