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

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

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.

A photo of several people standing in a field of cover crops that are about shoulder high.

Registration Open for Two Soil Health Schools!

The 2025 West River Soil Health School will be held June 25-26 in Caputa, SD, and the 2025 Soil Health School will be held September 3-5 in Huron, SD. Each of these two schools will feature outstanding instructors consisting of industry professionals, researchers, and experienced producers. The days will be split between classroom discussions and field exercises designed to help you improve your land and your profit margins through regenerative agriculture practices. Visit our events page to learn more about these excellent learning opportunities!

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News & Events

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Awards, new board member announced at Soil Health Conference

PIERRE, SD – The Ninth Annual Soil Health Conference, Jan. 15-16 at the Ramkota Hotel and Event Center in Watertown, SD, saw approximately 500 attendees, including over a hundred students. The South Dakota Soil Health Coalition was thrilled to offer this opportunity...

Noted rancher, author to explain ‘sweet spot’ of grazing at conference

By Janelle Atyeo For South Dakota Soil Health Coalition PIERRE, SD – Tom Krawiec found the sweet spot for grazing quite by accident. The Canadian rancher sought out the point where grass in his pasture was both established enough to stay healthy and nutritious enough...

Study finds soybean yields resilient following late rye termination

By Janelle Atyeo For South Dakota Soil Health Coalition PIERRE, SD – A cover crop of quick growing cereal rye can keep the soil in place over winter’s brown and blowing days. Its long roots soak up excess spring rains, and its straw helps block weeds. The more...