Written Evidence submitted by The University of Sheffield (SH0071)


1a.  How can the Government measure progress towards its goal of making all soils sustainably managed by 2030?

For soils to be sustainably managed both the quantity of soils must be maintained in situ, and their quality maintained, and improved where they have been degraded.  To measure progress towards the goal of making all soils sustainably managed by 2030 both in situ soil quantity (mass and volume) and soil quality must be maintained or improved at field-to-landscape scales- and data evidence is needed to measure progress towards the goal for both components.

Challenges: To confirm that soil quantity (volume and mass) is being sustained requires that rates of soil volume loss by erosion or oxidation of organic matter do not exceed rates of soil formation at the same location.  This requires that we at least know both typical rates of soil formation and typical rates of loss under different management, and environmental contexts.  This needs to take into  account the erosive environmental parameters for water, which are affected by rainfall, slope angles, soil texture and organic matter content etc. as well as management practices, as conceptualized in the Revised Universal Soil Loss Equation, fully parameterized for the UK.  Consideration of vulnerability to wind erosion also needs to be included, where shelter from trees and hedges can be important. 

Currently, we have no landscape-scale assessment of soil erosion rates in the UK, but there is evidence that this is a widespread problem contributing to long-term economic losses (Graves et al., 2015; https://doi.org/10.1016/j.ecolecon.2015.07.026).   Using cosmogenic isotopes Evans et al., (2019; SOIL, 5, 253–263, 2019 https://doi.org/10.5194/soil-5-253-2019) found that a fairly typical sloping arable field in Nottinghamshire is losing topsoil at a rate that, taking into account rates of soil formation, would deplete topsoil to 30 cm in approximately 250 years. 

Our personal experience of soil sampling arable land in England has been that on sloping ground there is always a step-down from the field margins into the cultivated parts of the field, except sometimes at the bottom of slopes, where soil may accumulate.  While much of the downslope soil loss is historical, the process is still actively occurring in many fields.  There is an urgent need to better monitor soil volumes and stocks, and to identify and control areas of erosion losses.

Even on flat land soil can be lost by wind erosion and organic matter oxidation, or insidiously through removal on root crops (Panagos et al., 2019); doi.org/10.1016/j.scitotenv.2019.02.009) - sugarbeet alone removes about 200,000 tonnes per year of prime arable topsoil in the UK-  which is not returned to the fields from which it originated.  This is not sustainable management of soil, even if the soil is now recovered in sugar beet factories (but then sold as topsoil for developers etc.).

An important conceptual development in assessing whether soil management is sustainable for soil quantity is the concept of soil lifespan, as defined by Evans et al., (2020).  This landmark publication provided the first robust, global assessment of top soil (to 30 cm) lifespans and how they are reduced or increased by agricultural management (Evans et al., (2020; Environ. Res. Lett. 15 0940b2 https://iopscience.iop.org/article/10.1088/1748-9326/aba2fd ).  This paper provides a compelling conceptual framework for assessment both of the sustainability of soil volumes- and the effectiveness of different practices to reduce net losses, which are prevalent under conventional arable management.  This study found that just under a third of bare soils (for example free of vegetation due to mouldboard ploughing and harrowing) in their dataset have lifespans of less than 200 years.  It is clear that reducing ploughing to an absolute minimum and following conservation agriculture practices to keep soil covered and vegetated for as much of the year as possible can substantially increase soil lifespans, with nearly 40% of soils under conservation agriculture having lifespans over 10,000 years.  

Recommendations for measuring progress towards sustainable management of soil stocks (volume and mass):

Reducing sediment loss via rivers, as indicated in the Government’s recent Environmental Improvement Plan is a laudable ultimate goal- but does not in itself guarantee that topsoil is not being lost from within fields in a manner that is incompatible with the goal to manage soils sustainably.  There needs to be investment in very high resolution LIDAR mapping of a national network of locations representative of land uses and slope angles complemented by targeted monitoring of soil depth at representative sites spatially distributed across the UK landscape.  The latter might be accomplished using a combination of  cosmogenic isotopes  (Evans et al., 2019 op. cit.) and a set of reference height survey points set up like Ordnance Survey benchmarks, to provide monitoring of in-field soil movement and losses on a decadal basis for land under representative different management practices. 

1b.  What are the challenges in gathering data to measure soil health and how can these barriers be overcome? 

Challenges: To sustain soil health (soil quality) requires two fundamental properties to be maintained, and in many cases improved – organic matter content, and soil structure (especially macroporosity). These two parameters, if maintained and improved, automatically help to maintain and improve soil biology- that require carbon energy, and pore spaces for good drainage and aeration. 

Recommendation for cost-effective monitoring of soil health.

The simple measure that integrates soil organic matter, structural quality and biological activity is the mass of organic carbon that is held in water-stable aggregates >2 mm and the amount of organic carbon held in the remaining soil fraction smaller than this  Using standardized wet-sieving to separate the two fractions, weighing the two fractions when dried, and then measuring their organic C concentrations provides a sensitive and effective measure of soil quality (Guest et al., 2022) https://doi.org/10.1016/j.scitotenv.2022.158358.

The reasons why these measurements are so useful are that water-stable macroaggregates are fundamental to mineral soil health as they help to control long-term organic C storage in mineral soils, and they help maintain macropore space in soils- facilitating both good drainage and nutrient and water storage capacity (Guest et al., 2022). Previous studies have shown that macroaggregates gradually saturate with organic carbon storage, so to store more organic carbon as this saturation is approached, more of the soil volume needs to be converted into water-stable macroaggregates.

Another reason why this soil component is so valuable for monitoring soil health is that the assembly of water-stable macroaggregates is driven by biological activities-  with interacting effects of earthworms, mycorrhizal fungi, plant roots and the rest of the soil faunal and microbial communities (Guest et al., 2022)Soils with good macroaggregation are biologically active, and support beneficial organisms. 

Consequently, the proportion of soil mass that is held in water-stable macroaggregates provides an ideal single proxy measure of soil structure, biology, and potential to store organic carbon-  core components of soil health. Furthermore, whereas measurements to monitor changes in bulk soil organic carbon typically take decades for statistically significant increases to be detected, the water-stable macroaggregate-bound organic carbon fraction is a highly responsive and early indicator of soil carbon sequestration and recovery of structural function.  For example, the mass of >2 mm water-stable macroaggregates increased more than 5-fold when 3 year grass-clover leys were  introduced into long-term arable fields (Guest et al., 2022).  This was accompanied by a 4.8 fold-increase in soil organic carbon stored in this soil fraction, whilst the 14% increase in bulk soil organic carbon in the same samples was not statistically significant (Guest et al., 2022).

Similarly, counting earthworms or undertaking soil biodiversity monitoring is time-consuming, expensive, and subject to considerable temporal variability linked to weather.  Macroaggregate-bound carbon is a more consistent proxy measure for biological health than monitoring the organisms that contribute to developing this property.

Since the proportion of soil and organic carbon in the different aggregate fractions will vary by soil texture class, using this monitoring approach it will be possible to establish guideline values for different soil types.  This provides an ideal method for landscape-scale soil monitoring of topsoil health.  It can be automated, and can be applied to capillary-rewetted samples that have been rapid oven-dried after sampling to preserve the biological aggregating agents from decomposition.   Topsoil samples with these aggregate fractions measured to a standard depth of 0-7 cm would be adequate for large-scale monitoring of soil health, providing additional data is collected on soil structure below this. Because soil health can be impaired by soil compaction, which can occur both in the topsoil and subsoil, it is also important to measure moist soil penetrometer resistance with depth to check for compaction, and to use this to guide management such as subsoiling.   

If the primary goal is monitoring soil health rather than soil carbon stocks (which is much more technically demanding and expensive), we recommend focusing only on the surface soil for sampling macroaggregates and organic carbon since the carbon concentrations and structure of the surface layers provide the primary control on soil functioning in absorbing water and draining.  Poor subsurface structure should be assessed by direct measurements using a penetrometer.



  1. Do current regulations ensure that all landowners/land managers maintain and/or improve soil health? If not, how should they be improved? 

No, current regulations do not ensure that soil erosion rates are consistent with soil lifespans that are sustainable for future generations, nor is soil health safeguarded.

There are no specific goals regarding reducing soil erosion within fields- current targets are focussed only on reducing sediment loss into watercourses.  The quality of farmland could progressively degrade if soil is lost into buffer strips and field margins like hedgerows, even if it does not reach rivers.

Soil erosion rates should be more thoroughly monitored across the field landscape, and land use practices incompatible with sustainable soil lifespans on major soil types should be more tightly regulated. 


Soil losses should be replenished by appropriate rock dust additions (such as basalt, which can improve soil health and sequester carbon – Kelland et al., (2020); https://doi.org/10.1111/gcb.15089) or by returning soil removed on root crops like sugar beet to the fields, and silt from dredging rivers should be returned to farmland, if uncontaminated.

The growth of forage maize and maize for anaerobic digestion should be very carefully regulated Authorisation to grow the crop should only be granted in circumstances where fields are not prone to erosion, or where the erosion risk is low, but significant, it should be under sown with evergreen ground cover that is maintained by appropriate row spacing to ensure soil is not left bare on harvesting.  Maize, together with root crops, are generally the most harmful to soil health and exacerbating unsustainable soil erosion losses.

Current regulations do not prevent soil organic matter depletion or continuing degradation of water-stable macroaggregates, which are vital for soil health.  Regulations should be tightened to enforce management to increase soil organic carbon concentrations, especially where these are substantially below the values that are achievable under cropping on each of the main soil texture types.   Guideline minimum values for returning organic matter to soils should be defined. Farmers should be financially rewarded for increasing soil organic carbon concentrations, especially in topsoil, and the water stable-aggregate bound soil organic carbon monitoring could provide a mechanism to do this cost-effectively...

3a. Will the standards under Environmental Land Management schemes have sufficient ambition and flexibility to restore soils across different types of agricultural land?

The ELMs are moving in the right direction, but currently lack sufficient ambition or specific goals with respect to soil health and soil sustainability to ensure that soils will be sustainably managed in future, and certainly are not on track to achieve the 2030 goalThe recent downgrading of the goal - to just 60% of soils on farms to be covered by sustainable farming agreements by 2030 means that there is no hope of achieving the original goal

Within the Sustainable Farming Incentive (SFI) scheme, the requirement in some options for farmers to add organic matter to soil once in three years does not define a minimum amount or form to be applied-  so this requirement is effectively meaningless and lacks any ambition. There are risks that this will encourage farmers to add organic matter more sparingly across their land, to notionally “tick the box” whilst what is really needed is attractive funding incentives that pay more for greater input rates.   However, depletion of soil organic carbon is widely recognized as the single most important contributor to economic losses and functional degradation of UK soils (Graves et al., 2015; https://doi.org/10.1016/j.ecolecon.2015.07.026.)

There are currently no specific targets for increasing soil organic carbon. Unless such targets are defined it is unlikely that the SFI and other farm payments will lead to restore soil health and ensure that soils are sustainably managed (i.e. that the quantity and quality of soil is maintained and improved). 

Carbon supplied to the soil through living roots (for example through evergreen perennial leys) is more persistent and more effective in improving soil aggregation and soil health than, for example, simply returning crop residues to soils, providing the root and shoot inputs are not compromised by overgrazing and excessive biomass removal in too frequent silage cutting. Cover cropping and minimal / no tillage require additional funding support to make them attractive options for arable farmers, as the current SFI payments are set too low with costs of soil tests and seeds etc. often exceeding the rates of payment offered last year. Less than 2% of the 84,000 farm businesses claiming Basic Payments joined the SFI scheme in 2022- Rural Payments Agency data. Furthermore, the payment rates do not appear to reflect the actual values of public goods and ecosystem services provided by these and other more sustainable practices than conventional intensive cropping- through reductions in water pollution, air pollution and greenhouse gas emissions, and increases in soil organic carbon sequestration and biodiversity.  These benefits need to be properly valued and rewarded if the “public money for public goods” philosophy is to be honoured.

Incentives should be provided for mowing and mulching legume-rich leys as this may be one of the fastest ways to rebuild soil heath and biota, including accumulating nitrogen and carbon stocks.  The resulting healthier and more fertile soil will reduce the requirements for nitrogen fertilizer in the following crops- so gives benefits of reduced greenhouse gas emissions associated with fertilizer manufacture (CO2, N2O) and use (N2O), and nitrate leaching.

In short, farmers signing up for the Sustainable Farming Incentives and following the proscribed managements are not automatically going to deliver sustainable soil management.  It may be more sustainable than in the recent past, but this does not make the management sustainable.  The land area or proportion of farmers that join these schemes cannot be equated to land areas that are managed sustainably (as the present government targets are suggesting). There needs to be evidence that the practices actually do deliver soil sustainability outcomes, not an assumption that this is the case.

3b. What are the threats and opportunities for soil health as ELMs are introduced? 

ELMs and SFI offer opportunities to incentivise and properly reward good practice and to help farmers achieve better soil management with improved environmental outcomes and to properly reward farmers for maintaining natural capital stocks and delivering environmental goods and services that are public goods, but have been taken for granted and not recognized financially.  The main immediate threat arising from the schemes are that the rates of payment have been insufficient to be attractive to many farmers, who therefore are continuing “business as usual”.  Secondly, the current incentive options are relatively short-term and do not currently offer a very effective way of long-term sustainably managing soils.  For example, the support for introduction of herbal leys into arable rotations offers no substantial additional funding reward for farmers maintaining the soil post-ley in no-tillage cropping. However, it is well established that a single year of ploughing of grassland or leys destroys most of the water-stable macroaggregates (Low 1972; J. Soil Sci. 23, 363–380. https://doi.org/10.1111/j.1365-2389.1972.tb01668.x ).  Furthermore, it reduces the populations of both earthworms (Edwards and Lofty 1982; Journal of Applied Ecology 19:723-734) and mycorrhizas (Garcia et al., 2007; Agronomy Journal 99:1093–1103) which are important in assembling macroaggregates, and it mineralizes much of the organic C accumulated in macroaggregates.

Direct drilling into 3-year grass-clover leys has been shown to maintain high mycorrhizal activity compared to long-term ploughed fields, and has the potential to save about 100 Kg N ha-1 fertilizer use, while maintaining near UK average yields of wheat (Austen et al., 2022; DOI 10.3389/fpls.2022.955985). Long-term (70 year) studies of arable- 3 year ley rotations where the leys are ploughed out show modest long-term increases in soil organic matter and soil health compared to continuous arable cropping (Johnson et al., 2017; Eur. J. Soil Sci. 68, 305–316. https://doi.org/10.1111/ejss.12415). This is the result of the cycle of soil health regeneration by the leys and then exploitation and degradation during the ploughing and cropping phase.

There is a need for greater incentives in ELMs and SFI for regenerative agricultural practices and minimizing soil disturbance. Newer technologies to allow crop establishment with minimal soil disturbance, such as direct drilling, which are much better at maintaining populations of beneficial soil organisms, are widely used throughout the world instead of fuel-intensive ploughing.  There is compelling evidence of the adverse effects of intensive tillage on long-term soil health, including impacts on biota, chemistry such as carbon storage, and structure such as macroaggregates, and resultant reductions in soil lifespans due to enhanced erosion. We need far more ambitious targets and attractive financial incentives and rewards in SFI and in ELMs to facilitate most farmers adopting these practices that demonstrably improve soil health and extend soil lifespans considerably (Evans et al., 2020).

  1. What changes do we need to see in the wider food and agriculture sector to encourage better soil management and how can the Government support this transition? 

Food produced from land that is very well managed, with high soil quality, and low environmental impacts should be supported with a sustainability brand mark defined by low greenhouse gas emissions, high nitrogen use efficiency, soil lifespans of >1000 years, and appropriate or increasing soil organic matter. Premium prices should be paid to farmers for food produced achieving these targets. Farmers producing food using management that ensures delivery of public goods and services such as improved soil health and soil carbon storage should be financially rewarded. Food that is produced by practices and management that degrades natural capital soil stocks and impairs soil health and functions should be financially penalized at farm-gate, and have additional costs added post-farm gate to cover reparation costs so that customers are not incentivised to buy cheaper products produced unsustainably.

  1. What does UK Government need to do to tackle other stressors on soil health such as soil contamination? 

Soil contamination needs to be managed using a risk-assessment process that is fit for purpose, and is not excessively over-precautionary or based on assumptions that lack realism- and in so doing result in excessive expensive and disruptive remediation, or unnecessary land use restrictions.  There remains considerable scope for refinement of the parameters used in the CLEA model to develop more accurate risk assessments, and the parametrization of thresholds used in the UK's category 4 screening levels (C4SL). For example, urban soils, which are often the most contaminated with heavy metals and persistent organic pollutants, are also frequently highly enriched in black-carbon soots (Edmondson et al., 2015; Environ. Sci. Technol. 49, 8339−8346; DOI: 10.1021/acs.est.5b00313). Black carbon behaves differently in soils to uncharred organic carbon, tending to be more effective at immobilizing toxic elements and organic molecules, and has greater persistence than organic carbon. In the past allotment sites in cities were closed down, or had large expenditures made to remove and replace contaminated soils, where the actual risks to human health were never demonstrated in the growers affected (see for example cases reviewed by Leake et al., (2009). Environmental Health 8 (Suppl 1):S6 doi:10.1186/1476-069X-8-S1-S6. This has been corroborated by more recent research that has shown that in urban horticulture in the UK, where the C4SL guidelines for lead were exceeded in 83% of the allotment soils sampled the bioavailability of that lead was very low, so unlikely to pose a significant risk (Crispo et al., 2021): https://www.sciencedirect.com/science/article/pii/S0269749121015426.  This is also supported by analysis of blood of people growing and consuming crops grown on allotment soils that would normally be assessed as “contaminated” (>80 mg kg-1 Pb) not differing significantly from that of neighbours not growing food (Entwistle et al., 2019). https://www.sciencedirect.com/science/article/pii/S0160412018313138, This research provides a method and approach that delivers empirical evidence that guideline values on the soil types tested would more appropriately be set to between 722–1634 mg/kg Pb. This kind of approach needs to be applied more widely so that risks from soil contamination are appropriately assessed and managed.  


February 2023