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.

2023 Soil Health School Registration Open!

The 2023 Soil Health School will be held August 28-30 on the farms of Anthony Bly and Bruce Carlson near Garretson, SD! There will be classroom sessions, field excercises, discussion panels, and opportunities to network with researchers, industry professionals, and experienced producers who can help you on your soil health journey! Class size is limited, so learn more and register today!

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News & Events

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Long-term research reveals advantages of diverse crop rotations

By Stan Wise PIERRE, SD – It can take time for scientists to build new knowledge of biological processes, especially when those processes play out over the course of years. Researchers with the U.S. Department of Agriculture-Agricultural Research Service North Central...

‘Park the chisel’: First step toward soil health can be simple

By Stan Wise PIERRE, SD – The benefits of improved soil health for agricultural producers and gardeners are numerous and valuable – reduced input costs, improved profitability, drought and flood resilience, reduced erosion, improved water quality, increased wildlife...

Saline Soil Management: More Money With Fewer Crop Acres

By Stan Wise PIERRE, SD – Salinity areas. Trouble spots. White deserts. Regardless of what they’re called, saline soils are a problem for South Dakota. White, salty areas where nothing grows are a common sight in fields across the state. “The amount of salinity that's...