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Ask a group of farmers what they want to learn more about today and chances are the most common answer will be soil.
Yet in England the soil grading system commonly referred to within agriculture is actually a land grade inherited from the planning system. Under the Agricultural Land Classification (ALC), land is graded between one for the highest quality land and five for the lowest quality.
Planning policy aims to protect what is known as 'the best and most versatile' (BMV) agricultural land and soils from significant, inappropriate or unsustainable development proposals. It achieves this by steering development away from BMV land (grades one, two and three a) and towards poorer quality land.
The ALC grading system assesses the limitations upon a site due to the interaction between climate, site and soil characteristics. This means it is considering issues such as the consistency of yields, productivity, ease of cultivation and versatility of land.
These are all valid agricultural considerations, but in practice soils with polar opposite characteristics can be classified as the same grade.
For example both heavy Lincolnshire clay soils and Cotswold brash soils can be grade three, because there are limitations to the range of crops which can be grown on them, but the reasons for this are very different. The clay soil will be deep and expensive to cultivate, it will yield consistently when cropped but it will be challenging to cultivate in wet autumns and consequently it is only suitable for a limited range of crops.
On the other hand the Cotswold brash soil is likely to be easier to cultivate but stonier and shallower meaning the yields of crops grown upon it can be vulnerable to a lack of moisture.
These differences illustrate that the ALC alone does not give farmers the full picture. It is also a fixed historic assessment so does not reflect aspects of soil quality which change over time.
Changing levels of soil organic matter are particularly significant as it affects soil physical, chemical and biological properties. Soil organic matter plays a role in aggregate stability, nutrient retention and availability and nutrient cycling. Biological life is another dynamic indicator of soil health, as microscopic bacteria, fungi, protozoa and nematodes play a role in the decomposition of crop residues and nutrient cycling.
There are commercial tests available to analyse all these aspects of soil quality or health in detail, but unlike the ALC a standardised soil quality indicator or series of indicators has not yet been developed. Frustratingly for many in the sector looking to incentivise soil health measures, soil quality remains difficult to evaluate and communicate.
Developing a widely accepted indicator of soil quality that meets agriculture’s needs is now a priority. There is a long-term ambition for public support for agriculture and land management to be based on outcomes delivered rather than on activities performed. So if soil health is to be enforced as a baseline or rewarded through public or private investment, it will be necessary to demonstrate the results of work to maintain or restore soil productivity.
A clear picture currently doesn't look likely to emerge. Defra’s Environmental Improvement Plan sets a target to publish a baseline map of soil health for England by 2028 and bring at least 40% of England’s agricultural soil into sustainable management by 2028. To help achieve this, the Sustainable Farming Incentive scheme promoted no-till and encouraged farmers to test their soil and develop a soil management plan. But the scheme is currently closed, and it wasn't capturing the results nationally or encouraging consistency.
There is also strong interest in the role soils can play in achieving net zero, but there is no accepted way to measure and monetise carbon sequestration in UK soils. The lack of a standardised assessment and monitoring scheme makes it hard to measure progress, and implementing one could help unlock this opportunity.
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