The VESS test (original guidelines developed by SRUC) assesses soil structure based on the appearance and feel of soil dug out with a spade.
In this test you observe and record how aggregated the soil structure is (aggregation is the crumb structure naturally occurs in healthy soil).
The scoring scale ranges from 1 – very good structure, to 5 – poor structure.
Aggregation is a product of biological action, normally the result of microbes gluing soil particles together into larger clumps (called aggregates). True biological aggregates have a rounded (crumb-like) appearance, like cottage cheese but on a smaller scale.
1. Locate your chosen sample site – you can use the GPS mapping feature on the app to do this if you’ve recorded the sample locations previously.
2. Dig out 3 sides of a square as wide as your spade, and dig down about 20 cm if possible.
3. Leverage the soil block out of the ground, (leaving one side undisturbed by the spade) and place on tray/bin bag.
4. Take a photo of the undisturbed side of the block.
5. Measure the depth of the turf layer, and add this as a note in the VESS test in the app.
6. Looking just at soil in this layer, begin to break it down gently in your fingers. Until you have clumps of soil about 1.5-2cm in your hand
7. Follow the VESS scoring guidelines here. The main questions are: Are the clumps angular? Do they have roots running through them? How easy is it to break them down? How porous are they? With gentle pressure breaking them down what size are most of the clumps?
8. Record the VESS score in the app.
Don’t get too hung up trying to get the exact score. You will get quicker and understand the scoring better with practice.
Read this article to find out how many times to do the VESS test in each field.