Agribusiness News November 2023 – Inputs: Soil Health

In the past soil has been seen as a medium for growing crops, including grassland swards. The main focus has been on the nutrients that are available from the soil to support the yield and quality of the growing crops. Efforts were mainly focused on the addition of these nutrients to ensure sufficient were available for growth and usually added in excess to ensure a plentiful supply.

Soil health legislation

Thinking has changed in the last 15 to 20 years and a more rounded view of the soil has emerged. This has encompassed the soil health of the soil which has been defined by the Intergovernmental Technical Panel on Soils (ITPS) in 2020 as ‘the ability of the soil to sustain the productivity, diversity, and environmental services of terrestrial ecosystems’.

The concept of soil health covers three main areas within the soil: chemistry (which is still very important), physics (the structure of the soil) and biology (the soil as a living medium). Some of these areas have become incorporated into government strategies and policies for soil across the UK. This is true in Scotland, where the main report is still the Scottish Soil Framework, which lists the pressures on soil. It indicates that although there are a number of policies in place for the protection of aspects of some soils, there is not one policy for the overall protection of the soil.

The EU is conscious of the deterioration of European soils, with an acknowledgement that an estimated 60 to 70% of soils in the EU are not healthy. Additionally, it understands that soils are still subject to further decline as a result of erosion, compaction, organic matter decline, pollution, loss of biodiversity, salinisation and sealing. As soils do not receive the same protection in the EU as air and water, this year on the 5^th July the EU proposed at new law to attempt to ensure all EU soils are in a healthy condition by 2050. This would require monitoring of soil health so appropriate action can be taken to maintain soil fertility and yield, with sustainable soil management becoming the norm.

What has been considered for Soil Health?

It is significant that soil health is now being considered and the impact of poor soil health receiving more focus along with attempts for its maintenance and enhancement. However, we need to consider how healthy is a soil. We need a way of measuring and then monitoring soil health that is not too costly or time consuming but still provides useful results for management. SRUC researchers, in partnership with AHDB and through consultation with experts and industry are exploring robust methods for monitoring soil health.

Soil Indicators

A set of soil indicators needed to be developed that had broad agreement and were suitable for a range of agricultural practices. The final suggested indicators comprised of soil pH, extractable Phosphorus (P), extractable Potassium (K), extractable Magnesium (Mg), Soil Organic Matter (%), soil structure – using the Visual Evaluation of Soil Structure (VESS), and earthworm numbers. The results of these assessments were considered in relation to bands that had been agreed, through previous research, publications and expert opinion, to be placed in traffic light-coloured ranges that gave an immediate visual interpretation. These related to actions, if the results were to be investigated (red), monitored (yellow) or no immediate action required (green). Colour coded scorecards could then be created to allow management decisions to enhance the soil quality in any areas of a field that needed attention.

Additionally, the soil indicators need to be relevant to the soil texture in the field, to inform management decisions. An example is given in Figure 1, where three fields have been assessed and the traffic light system: Field 1 (Grassland) has the poorest soil health and needs attention for the soil structure and potassium with further nutrient and liming recommended; Field 2 (Grassland) has good soil health; and Field 3 (Arable) needs more organic matter, consideration of the some of the nutrients i.e. K and Mg and concern about the soil structure to prevent it deteriorating further.

It is encouraging that soil health is now being considered in relation to the maintenance and sustainability of soils. Regular assessments and the use of soil scorecards are a major step forward as they can be used for benchmarking with other comparable soil types to understand what makes a good soil more needs to be done on the longer-term monitoring of the soils to ensure they remain profitable for years to come.

Paul Hargreaves, paul.hargreaves@sruc.ac.uk