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.

2024 Soil Health Conference Registration Open!

The 2024 Soil Health School will be held Jan. 23-24 at the Best Western Ramkota Hotel in Rapid City, SD! Keynote speakers include Jay Fuhrer, Jerry Hatfield, Glenn Elzinga, and Zach Smith. There will be many other speakers, breakout sessions, and opportunties to network and socialize! Join us and be a part of our 2024 Soil Health Conference!

Learn More and Register

News & Events

VIEW ALL News & Events

Wintertime is decision time

By Stan Wise PIERRE, SD – It’s often said that the best time to start improving your land was 20 years ago, but the second-best time is right now. That statement might be harder for ranchers to swallow with winter on their doorstep, nothing growing in their pastures,...

Research ties healthy soil biology to a host of benefits

By Stan Wise PIERRE, SD – Agricultural producers often base their land management decisions on the living things they can see above the ground – crops, livestock, forage, weeds, insects, wildlife, etc. However, new research is showing they should also consider life...

Student video and essay contests now open

As part of the 2024 Soil Health Conference, the South Dakota Soil Health Coalition has announced two exciting contests for students in South Dakota. The student video and essay contests have been designed to give students the opportunity to learn more about soil...