Ruth Ruddell, a Technologist with the College of Agriculture, Food and Rural Enterprise, explains how farmers can complete a VESS.
A healthy soil will have the ability to store and supply nutrients, and this function relies on a number of soil properties.
With costs increasing, it is more important than ever that we assess soil health and nutrient status, so you can address any limiting factors before the growing season.
You can recognise a healthy soil by the ability of the physical, chemical and biological aspects to fulfil their functions.
Issues in any of these three areas will limit plant nutrient uptake and yields. To improve soil health, you must first assess each aspect to establish what would reduce your soil function.
Complete a VESS
Completing a visual examination of soil structure (VESS) will allow you to assess the physical status of your soil.
Use a spade to dig soil pits (20cm x 20cm x 20cm).
Then manually break down a sample of soil, by hand, to visually assess the structure of the soil particles, rooting depth and colour/smell of the soil.
A well-structured soil has round crumbly particles that can be easily broken up between your fingers, allowing plant roots to penetrate down through the soil.
The soil should smell earthy or have little odour; if there is a pungent smell, this indicates poor drainage or lack of oxygen in the soil.
Digging a soil pit will also allow you to determine if compaction and/or poor drainage is an issue.
Compaction can lead to poor root growth and penetration with reduced soil air spaces.
Reducing soil air spaces causes anaerobic (the absence of air) conditions in the soil.
This has a negative impact because the soil organisms and plant roots live and function in the pore spaces.
Avoiding soil damage
Compaction also reduces the capacity for water to infiltrate and drain through the soil.
Management practices that can avoid damage include:
- Restricting animal and machinery traffic when soils are vulnerable or wet;
- Working with lighter axle loads and lower ground pressure tyres;
- Or, if applicable, use remediation measures like subsoiling or aerators.
Soil organic matter is essential for many processes that control nutrient supply and storage in soils. Organic matter varies depending on the soil texture, rate of decomposition, and environmental factors such as aeration and soil temperate.
There will be higher organic matter levels under grassland compared to continuous arable rotation.
Organic matter levels are highest near the surface and decreases with depth, typically ranging between 1 and 6%. Low organic matter levels will impede the soil’s ability to provide soluble forms of nutrients.
Increase the level of soil organic matter
You can increase the level of soil organic matter by incorporating crop residues while optimising grazing management will help incorporate grass residues and animal manure into the soil.
Applying farmyard manure and slurry to crop requirement, combined with the application of lime to correct soil pH, will improve plant growth.
It will improve soil structure by making clay more porous and sand more water retentive.
Choosing plant species with greater rooting depths, for inclusion in your sward, will increase and distribute the organic matter to greater depths within the soil profile.
Also, protect existing organic matter levels by avoiding poaching of the soil; this will limit the loss of soil by erosion by wind and rain.
Consider minimum cultivation methods as they reduce the rate of organic matter decomposition compared to conventional cultivation.
The benefit of optimal organic matter levels will:
- Increase the resilience of crops/swards to adverse weather;
- Improve nutrient holding and availability;
- Increase carbon storage;
- Improve water infiltration and traffic-ability of the soil.
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