This 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. For each spade-full you are encouraged to do two VESS readings, one for the top layer of soil, and another for the soil below, as well as measure the depth of each. Usually the top layer scores better, and as the soil improves over time the top layer will get deeper, so it’s important to record top depth.
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.