Physical Properties – OLD

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.

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Soil Health School

The 2026 Soil Health School is set for September 15-17 near Twin Brooks and Marvin, SD.

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Small Scale Ag
Soil Health School

The 2026 Small Scale Ag Soil Health School is set for Aug. 28 in Huron, SD.

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News & Events

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Test grain for nitrates before using it as forage

By Stan Wise With the vast majority of South Dakota in a drought and experiencing high temperatures, grain producers are having to make some tough decisions about their crops. Will those grains produce enough yield to make harvesting them a financially viable option,...

Darling Creek Ranch Named 2026 SD Leopold Award Winner

Sand County Foundation Dan and Sharon Anderson’s Darling Creek Ranch has been selected as the 2026 South Dakota Leopold Conservation Award® recipient. The $10,000 award honors ranchers, farmers, and forestland owners who go above and beyond in their management of soil...

Building operational resilience with soil health

By Stan Wise South Dakota Soil Health Coalition PIERRE, SD – Resilience. It’s one of the prizes that keeps conservation-minded land managers striving for improved soil health. Operational resilience in the face of floods, market fluctuations, rising input costs,...