Soils are complex systems that are important in providing and sustaining the landscapes they support.

However, they are built up of three main components – physical, chemical and biological and these need to function together to create and maintain this vital resource.

In the past, the main focus for agricultural soils has been on the chemical (pH, organic matter and nutrient levels) attributes but this is now changing as the influence of the physical (gas movement and soil structure) and biological (biodiversity and nutrient cycling) aspects of the soil are more understood.

Soils could be described as our greatest national wealth and now is the time to assess the health of those soils, ensuring all three components are supporting each other for sustained production.

Establishing what your baseline soil health and nutrient status is allows you to make management decisions which could reduce your future inputs costs, improve the efficiency of the farm business, benefit the environment and help reduce the impacts of climate change.

The current fertility of some Scottish soils can be an indicator of just how much quality has been lost. Recent research studied 1000 soil samples collected in South-west Scotland and found that more than half had a soil pH below 5.7. A pH closer to neutral would be optimum for crop growth that area, somewhere around 6.2 to 6.5.

This would ensure that the soil chemistry is operating as efficiently as possible and the nutrients applied as fertiliser are not lost with a cost to the farmer and the environment but are utilised by the growing crop.

Recent work at SRUC, in Dumfries, has shown that damaging the structure of the soil through compaction in grassland fields, combined with poor weather conditions, can reduce dry matter yield by as much as 14% annually from compaction by heavy tractor traffic or 12% by cattle trampling.

These reductions were seen to be greater for individual silage cuts, with yield losses for first cut silage between 10% for trampled pasture to 37% after tractor traffic.

The environmental effects of greenhouse gas (GHG) emissions and the loss of soil carbon are receiving increased attention as public concern over global warming grows. Agriculture and land use contribute to around a quarter of Scotland’s annual GHG emissions.

Government targets of an 80% reduction in emissions of GHGs by 2050 will require agriculture to further reduce current GHG emissions. Sequestration of carbon in agricultural soils is an important strategy in the effort to mitigate carbon dioxide (CO2) emissions to meet obligations under climate change agreements.

Emissions of nitrous oxide (N2O) in the UK, contribute around 8% of overall GHG emissions. Nitrogen from fertilisers can be lost as N2O gas produced by soil micro-organisms. In addition to fertiliser application, soil structure, soil water content and temperature influence N2O emissions.

Poorly drained or fine-textured soils, prone to wetness or compaction problems, are likely to produce most N2O and in addition, methane (CH4).

Compacted conditions could result in less fertiliser N being available to crops through increased surface run-off, as well as stimulation of anaerobic microbes that break down nutrients in the soil, increasing the amount of N lost to the atmosphere (as N2O).

In comparison to arable cultivation, grassland GHG emissions are generally higher due to increased soil compaction and wetter climatic conditions. The major sources contributing to grassland CH4 emissions are both livestock enteric emissions and excreta emissions (slurry storage and after spreading).

Production of CH4 from grassland soils is highly variable but generally increases immediately after slurry application and organic applications. Organic soils are more likely to act as a source rather than a sink of CH4.

Carbon sequestration is the capture and storage of carbon from the atmosphere in carbon sinks (such as oceans, forests or soils) through physical or biological processes (eg photosynthesis).

Soil contains around twice as much carbon as the air, and over half of that is found in the topsoil. Carbon levels are determined by the balance of net carbon inputs (eg vegetation, crop residues, organic amendments) and net carbon losses through organic matter decomposition (ie oxidation by microbes) and soil erosion losses.

Long-term use of ploughing and other cultivations that expose soil organic matter to oxygen (thus causing it to break down to CO2) can lead to carbon losses but erosion of bare soils from the action of wind, water and tillage drives the largest carbon losses.

There are some relatively easy changes to farming systems that can help increase farm efficiency and reduce GHGs. For example, reduced and no-tillage practices will reduce soil disturbance and carbon losses.

Growing cover crops on otherwise bare ground and maintaining a rough surface on sloping ground will minimise soil erosion. Nutrient management using long term manure applications can boost soil carbon whilst making good use of resources.

Crop rotations that include grass and clover leys build up soil organic matter and fertility (when designing a rotation consider nitrogen fixing crops and including crops with varying rooting depths). Afforesting highly degraded or marginal soils will significantly reduce soil erosion and actively sequester carbon.

As well as increasing the abundance of beneficial organisms or ‘bugs’ in the soil, organic fertilisers, composts and amendments also help improve the structure of the soil which helps root growth, increases drainage and should result in more vigorous plants better able to fight off pests.

Soil testing is a vital first step toward successful soil nutrient management so submit samples for testing the pH and nutrient status of your fields. However, the identification of poor soil structural conditions can be done simply using a spade (using tools such as VESS before the winter weather arrives.

Check the biological health of moist soils by recording worm counts from the same spadeful of soil used for VESS. Health tests are now readily available and can be likened to a MOT for your car or a check-up at the doctors, allowing management decisions to be made to sustain the valuable resource that is soil.