Watch: Using VESS for the visual examination of soils
Visual Soil Examination and Evaluation (VSEE) techniques are procedures for visually and tactilely evaluating soil structure.
Techniques have been designed to examine both the topsoil and subsoil, focusing on the impact of management on soil structural quality. Some procedures are semi-quantitative and include scoring frameworks, allowing visual assessments to be quantified.
Despite their apparent simplicity, techniques have been found to closely correlate with a number of quantitative soil measurements. VSEE techniques are quick to conduct, have the ability to holistically examine soil structure while generating immediate results by means of inexpensive and simple equipment - making them accessible to a range of users. VSEE techniques are therefore useful tools for both research and practical soil management.
Figure 1: A sample exhibiting good soil structural quality
Figure 2: A sample exhibiting poor soil structural quality
The VESS method
VESS (Visual Evaluation of Soil Structure) (Guimarães et al., 2011; Ball et al., 2007) is an example of a VSEE technique and is one of the quickest methods to conduct. VESS should be conducted a number of times in both representative areas within a field and in areas where compaction is known to have taken place.
How to conduct VESS?
Carefully dig an intact soil sample block out of the ground and place it on a plastic sheet or tray. Identify any horizontal layers of different structure and record each layer’s thickness in centimetres. Assess each layer separately. Systematically work through the VESS score sheet by carefully breaking-up the layer by hand to reveal the soil aggregates.
- Assess the size and shape of the aggregates. Are they rounded or sharp and pointed?
- Break open the aggregates and assess the porosity (voids and spaces) within. Are cracks and pores visible or are aggregates solid dense blocks?
- When breaking up the aggregates, note how easy it is to break them. Do aggregates crumble easily or does it require effort to break them?
- Examine the roots, do they grow throughout the layer and within aggregates or are they distorted and restricted to cracks between aggregates?
- Assess the soil colour, are orange blotches visible or are blue/grey zones present?
Apply the score that best describes the soil properties. Conduct the same assessment on any other layers found within the sample block. To get an overall score, simply multiply the score for each layer by the thickness of the layer. Add these layer scores up and divide the result by the total depth of the sample block.
Watch: Visual Evaluation of Soil Structure
For more information on how to conduct a GrassVESS, click here.
This article first appeared in the Signpost Programme newsletter for May. For more information on the programme and to sign up to future newsletters, click here.