Soil structure and its stability affect the movement and storage of water, aeration, erosion, biological activity and growth of crops. This short demonstration explains how aggregate stability can be measured. Authors Tianna DuPont, Andy McGuire, David Granatstein, WSU Extension. Recording from WSU virtual workshop Soil Health in Orchards with project support from the Washington State Tree Fruit Research Commission.
Text Transcript and Description of Visuals
| Audio | Visual |
|---|---|
| Soil structure and its stability affect the movement and storage of water, | Title card reading “Soil Structure”, shown over a close up image of soil held in a gloved hand. |
| aeration, erosion, biological activity and growth of crops. | A hand holds a clump of soil and gently moves it, showing the soil breaking apart. |
| Soil aggregates form when soil is clumped together. | Close up shot of soil that has formed into small clumps. |
| Large and medium size aggregates are held together by plant roots, | A hand holds a plant root which has larger soil clumps hanging off of it. |
| fungal hyphae and organic compounds from bacteria and fungi. | Close up shot of soil that has formed into small clumps. |
| The smallest aggregates are held together by clay and iron and aluminum oxides. | Title card reading “Aggregate Stability” over a person working setting up a soil demonstration at a table in an orchard. |
| One indicator of soil structure is wet aggregate stability. | A hand places small soil aggregates into labeled white containers with mesh bottoms and briefly holds one up to the camera. |
| Considered related to erodibility, soil with more water stable aggregates also has more pore spaces to hold air and water for plant roots. | The containers holding the soil aggregates are arranged in a row in front of a clear plastic container filled with water. |
| This demonstration mimics how we measure water stable aggregates in the lab. Select aggregates of the same size from different soils and place them on the screen. | Hands place the containers into the water. |
| Lower the screens into the water and observe the aggregates. Does the aggregate dissolve in the water or hold together? | Overhead view of labeled containers in water, showing differences in how the soil aggregates appear in each container. |
| After 5 minutes raise the sieves out of the water and dip 5 times. Assess how much of the aggregate is left on the screen. Repeat for several aggregates to get an average. | Each container is lifted out of the water and dipped back in repeatedly. After dipping, the soil appears different across containers, with varying amounts of soil left on the mesh and material visible in the water. |
| Good aggregate stability will help maintain macropores, reduce surface crusting, promote aeration and reduce erosion. | The containers are held up to the camera for comparison. Some aggregates remain compact, while others have dispersed into the water. |
| End card displays “Soil Health in Orchards Workshop” with an illustration of a tree and links to additional workshop resources. |
Link to YouTube video: Soil Structure Demonstration: Aggregate Stability
