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.

Registration Open for 2026 Soil Health Conference!

The 2026 Soil Health Conference will be held Jan. 13-14 in Aberdeen, SD. Don't miss this outstanding opportunity to learn more about soil health land management practices! In addition to the keynote speakers, this conference will feature breakout sessions, discussion panels, award presentations, demonstrations, vendor booths, student contests, and more! This is a chance to network with experienced sustainable agriculture producers and experts and brainstorm solutions for your land management challenges!

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News & Events

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Fall harvest reveals wildlife benefits of soil health

By Janelle Atyeo for South Dakota Soil Health Coalition PIERRE, SD – Judging by the number of pheasants stirred up from his fields during corn harvest, Craig Stehly was anticipating a bountiful hunting season. He attributes that to the weather, a good hatch this...

Interseeding Alfalfa for Soil Health

By Stan Wise Late summer is a good time for producers to inspect their alfalfa fields and address any problem areas. If there are any bare spots or a stand reduction caused by heat stress, flooding, drought or cold temperatures the previous winter, producers can seed...

Consider herbicide residual impact when planting cover crops

By Lura Roti For South Dakota Soil Health Coalition PIERRE, SD – Cover crops are an increasingly popular land management tool capable of providing a numerous agricultural benefits including improved soil health, weed control, and additional revenue streams for...