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Soil structure: Granular

Strong, fine and medium granular soil peds (L)

 

Soil Peds are aggregates of soil particles formed as a result of pedogenic processes; this natural organization of particles forms discrete units separated by pores or voids. The term is generally used for macroscopic (visible; i.e. greater than 1 mm in size) structural units when observing soils in the field. Soil peds should be described when the soil is dry or slightly moist, as they can be difficult to distinguish when wet.

 

In granular structure, the structural units are approximately spherical or polyhedral and are bounded by curved or very irregular faces that are not casts of adjoining peds. Granular structure is common in the surface soils of rich grasslands and highly amended garden soils with high organic matter content. Soil mineral particles are both separated and bridged by organic matter breakdown products, and soil biota exudates, making the soil easy to work. Cultivation, earthworms, frost action and rodents mix the soil and decreases the size of the peds. This structure allows for good porosity and easy movement of air and water. This combination of ease in tillage, good moisture and air handling capabilities, and good structure for planting and germination, are definitive of the phrase good tilth.

 

There are five major classes of macrostructure seen in soils: platy, prismatic, columnar, granular, and blocky. There are also structureless conditions. Some soils have simple structure, each unit being an entity without component smaller units. Others have compound structure, in which large units are composed of smaller units separated by persistent planes of weakness.

 

For more information about describing and sampling soils, visit:

www.nrcs.usda.gov/resources/guides-and-instructions/field...

or Chapter 3 of the Soil Survey manual:

www.nrcs.usda.gov/sites/default/files/2022-09/The-Soil-Su...

 

For additional information on "How to Use the Field Book for Describing and Sampling Soils" (video reference), visit:

www.youtube.com/watch?v=e_hQaXV7MpM

 

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Uploaded on February 9, 2010
Taken on September 4, 2007