Perform a spade test - VESS

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VESS spade test - layout

The VESS test (Visual Evaluation of Soil Structure) is a spade test method used to determine the soil quality (Sq) based on aggregates and porosity. By assigning a score from 1 (friable) to 5 (very compact), this test allows comparison of soil structure across different plots and farms.

This score is established by following the method below and based on the 2019 VESS chart.

This visual evaluation method of soil structure was developed by the Swiss agronomist researcher, Pascal Boivin.

Test description

Field methodology

Spade test equipment

• Equipment : Spade, meter, camera, paper, pencil, tarp.

• When : Avoid soil that is too dry (hard) or too wet (deformable). Avoid recent soil work. Prefer a time when roots are clearly visible.

• Where and how many? 5 samples are necessary to evaluate a homogeneous plot.

Extracting a soil block with "pre-hole". Illustration: Gabriela-Loza.com

• How to proceed?

1. Extract a soil block with the spade at 25 to 35 cm depth.
   • Do not trample or compress the area to be evaluated with the spade.
   • It may be useful to make a "pre-hole" to facilitate block extraction.
   • For tilled soils, the block must include the plow pan.
2. Open the block and handle carefully to reveal possible compact layers.
   • Either by opening the block like a book to reveal the structure.
   • Or by removing compaction marks caused by the spade.
3. Identify the layers.
   • Observe if there are changes in soil structure (compaction, size and shape of aggregates or clods, root behavior) and identify the number of layers with different structures.
   • Measure the thickness of each layer.
   • Score each layer individually using the evaluation grid.
4. Observe and score the aggregates and clods.
   • Start by observing whole aggregates/clods to evaluate their general size and shape (rounded? angular?).
   • Identify which score this corresponds to in the grid.
   • Then open (break) these aggregates/clods to reveal their internal structures (are they composed of smaller aggregates? Are they porous? Do roots pass everywhere?).
   • Confirm (or not) the chosen score.

Calculation of the overall block score

Example of VESS score calculation

Block score = [(layer_1 thickness x layer_1 score) + (layer_2 thickness x layer_2 score) + (layer_n thickness x layer_n score)] / total block thickness

Calculation example: Block of 27 cm including a 9 cm thick layer scored Sq2 and an 18 cm thick layer scored Sq3.

Block score = [(9x2)+(18x3)]/27 = 2.7

OAD

The mobile app VESS (Hepia) will help you evaluate and calculate your block's overall score.

Adaptation for disturbed soils

These soils are more heterogeneous than natural soils. Different structural qualities are not only distributed vertically in layers but also laterally within a layer. Therefore, for each layer, note the proportion of each type of structural quality and calculate a weighted average of these scores for the layer. The weighted average of the layer will then be used to calculate the weighted average of the block. This approach also allows keeping track of observed heterogeneity.

VESS chart

The two tables below group the characteristics used to assign a score to the different soil horizons.

Click to enlarge.

Sheet from the methodological guide of the spade test Structure and Action of earthworms, by Agrotransfert.

Sheet from the methodological guide of the spade test Structure and Action of earthworms, by Agrotransfert.

Detailed articles on each soil structure quality with photos : {{#DPL: Category=Qualités de sols VESS | ordermethod=title }}

Sources and annexes

• Page created from the sheet "VESS2020 Visual evaluation of soil structure" developed within the STRUDEL project (www.strudel.agroscope.ch). Alice Johannes (Agroscope), in collaboration with Peter Weisskopf (Agroscope), Pascal Boivin (hepia), Karine Gondret (hepia), Saskia Leopizzi (hepia), Frédéric Lamy (Changins), François Füllemann (DGE Vaud), Hubert Boizard (INRAe), Denis Baize (INRAe), Bruce Ball (SRUC), Joanna Cloy (SRUC), Lars Munkholm (Aarhus University), Rachel Guimarães (UTFPR) https://www.progres-sol.ch/fileadmin/progres-sol/VESS2019.pdf
• VESS Visual evaluation of soil structure quality https://www.progres-sol.ch/outils/vess.html
• Agro transfert guide (Downloadable here)
• Smartphone and iPhone app is available to help you perform your spade test.
• Method developed by ISARA : https://orgprints.org/id/eprint/32099/1/peigne-etal-2016-GuideTestBeche-ISARA_Lyon.pdf