To evaluate soil structure in grassland systems, one of the most practical methods available is the Grass VESS test, a visual, tactile technique based on the Visual Evaluation of Soil Structure (VESS) method.

What is VESS?

The Visual Evaluation of Soil Structure (VESS) is part of a broader set of Visual Soil Examination and Evaluation (VSEE) techniques. These approaches often involve carefully extracting a block of soil, breaking it apart, and assessing key physical features such as porosity, aggregate size and shape, and root growth.  Where compaction might occur deeper in the soil profile, such as in a tillage system, these same features are examined in situ through an alternative VSEE, known as the Double Spade method.

Although simple and inexpensive, VESS scores have been shown to strongly correlate with quantitative soil quality indicators. This makes the method a valuable tool for both researchers and farmers looking to assess and improve soil health.

Why conduct a Grass VESS

Grass VESS adapts the standard VESS method to grassland systems.

It is designed to assess two main layers:

• The Root-mat layer (Rm): the top 6 cm, or the depth of the root zone if it is clearly distinct.
• The Lower Portion (Sq): the soil beneath the root-mat down to a depth of around 20 cm.

Each layer is assessed separately, then scored using a structured framework. The results can tell us whether management practices are maintaining, improving, or degrading soil structure.

Learn more about soil structure: The Soil Structure A B C – A practical guide to managing soil structure

The Grass VESS test has several advantages:

• Fast: takes around 15 minutes per site.
• Inexpensive: requires only a spade, tray, and score sheet.
• Accessible: suitable for farmers, advisors, students, and researchers.
• Action-oriented: results can directly inform management decisions, such as reducing machinery traffic, altering grazing intensity, or considering soil remediation practices

How to conduct a Grass VESS

Choose your sampling locations

Assess two grassland areas with contrasting management practices or where one exhibits clear signs of physical damage to allow for comparison. At each location, use a spade to extract an intact soil block.

Extract the soil block

Dig a hole wider and deeper than the intended sample block. Avoid standing on or leaning the spade against the sample block. Mark out and carefully loosen the sample block using straight spade insertions. Carefully lever out the sample block with the spade and place it on a plastic sheet or tray.

Separate the layers

Using a knife or trowel, open the sample block like a book. It is fine to use the sward to gently pull the sample apart

Identify the layers of different structures

Measure and record the depth of the root mat and the overall sample. If no distinct root mat layer is present, treat the upper 6cm as such.

Assign scores

Using the How to conduct GrassVESS factsheet, conduct the assessment. First, examine the lower portion and then the root mat layer. Record the results.

Interpret results

Low scores indicate that land management is not negatively impacting soil structure. High scores indicate that management is negatively impacting soil structure and changes in management or remediation practices, may be necessary.

Repeating the assessment a number of times in the one location improves the accuracy of the result.

In this video we show you how to conduct the GrassVESS test

Teagasc are hosting Soil Health Week, from Monday, 22 September to Friday, 26 September, a dedicated weeklong initiative designed to support and inspire farmers, students and the general public with the latest insights, innovations, and practical guidance on soil health.