Securing long-term ecosystem function in lowland organic soils (SEFLOS)

Lead Research Organisation: Bangor University
Department Name: Sch of Natural Sciences

Abstract

The UK produces 58% of its own vegetables which have an estimated economic value of £1.2 billion annually. Many of these are produced on the lowland fen peatlands within the East Anglia region. This is particularly the case for field-grown salad vegetables with these peatlands supplying the majority of salad vegetables to all the major UK supermarkets. While these soils are recognised as being super-productive, they are also highly susceptible to damage which is threatening their long term economic future. For example, the average rate of soil loss from a combination of wind erosion and microbial breakdown of the peat lies in the region 1-2 cm depth per year. It is also widely predicted that the rate of loss is likely to increase with climate change making it a fragile resource. Some of the more shallow peats have already been completely lost, while the deeper peats have a finite lifetime estimated to be in the region of 75-125 years unless something is done to reduce the rate of soil loss. The recent House of Commons Environmental Audit Committee report on Soil Health identified the loss of soil from cultivated peatlands as one of the greatest threats to soil security in the UK. In response to this, our project aims to work with the horticultural industry and other key organisations to investigate new ways to save these peatlands from further rapid degradation and a loss of natural capital. We will focus on trying to reduce both the biologically-mediated loss of soil carbon and also the physical wind erosional loss of soil. We hypothesise that active management of the water table at strategic times of the year (e.g. during winter when there is no crop in the ground) can be used to reduce microbial activity in the soil and reduce losses of peat in the form of CO2. However, this must be done in such a way that it doesn't increase the release of other greenhouse gases (CH4, N2O) or result in other negative impacts on productivity or on soil quality. In addition, usin outdoor mesocosm trials, we will explore other potential synergistic strategies that may complement water table intervention as a soil conservation measure (e.g. use of nitrification inhibitors, cover crops etc). As our knowledge of the amount of soil lost by wind erosion remains poor, we will also use field monitoring and controlled wind tunnel experiments to get a better quantitative estimate of this loss pathway. This will allow growers to decide on whether to invest in protective technologies that might reduce erosional losses (e.g. soil physical binding agents, winter cover). While this project will generate lots of fundamental knowledge on peatland behaviour under different management scenarios, it is important that the research also recognises the socioeconomic context in which these agricultural systems operate. A key part of this project will therefore be to evaluate the social, economic and environmental impacts of the alternative strategies and compare these against the business-as-usual scenario. To facilitate this, a stakeholder workshop at the start of the project with representatives from industry, environmental regulators and policymakers, local drainage boards and conservation bodies will be used to actively steer the project towards outcomes that are both practical, economically viable and provide the best environmental outcome. This will be complemented by a final engagement workshop towards the end of the project where the barriers to technology adoption are explored. This will lead to the production of a grower- and policy-orientated roadmap for future preservation of this fragile soil resource and will have a focus on balancing economic and environmental sustainability. Ultimately, the research simultaneously aims to protect this soil resource for generations to come whilst maintaining profitability, productivity, and UK government's desire for sustainable intensification, greater food security and reduced greenhouse gas emissions.

Planned Impact

We propose a multifaceted way of disseminating our project findings and realising impact. We will build on our experience of previous and current RCUK funded projects. Key target audiences include:

INDUSTRY: This research proposal is directly underpinned by industry. To maximise impact and to facilitate knowledge exchange (KE), we have teamed up with the major industry involved in horticultural production on lowland peatlands in the UK (G's Ltd) and their network of individual producers (G's Growers Ltd). Part of the KE activity will be achieved by placing the experimental trials on the farms owned by G's. Secondly, G's will have a representative (Dr Ed Moorhouse) on our Management Board and who will attend the management meetings. Lastly, the inception and final stakeholder workshops will be co-organised with G's and held at the Ely office. These meetings are designed to engage with stakeholders who have an interest in managing lowland peats both inside and outside of horticulture (e.g. RSPB, Natural England, Water Management Alliance/Internal Drainage Boards, Fens For The Future Partnership). Together, our stakeholders will provide invaluable guidance throughout the project and will facilitate the dissemination of the project findings.

POLICY COMMUNITY: The recent House of Commons Environmental Audit Committee report on Soil Health identified the loss of soil carbon from cultivated peatlands as one of the greatest threats to soil security in the UK. There is therefore a very strong high-level policy interest within UK government (Defra, DBEIS) and its devolved administrations (Welsh and Scottish Government) in quantifying and mitigating emissions from cultivated peat soils. The findings of our research will therefore contribute to meeting the UK's climate change targets, whilst simultaneously achieving a sustainable, economically viable agricultural sector within these vital crop-producing regions. Through our existing high-level interactions with key government departments and international committees (e.g. IPCC) we can ensure that the information generated by this project will realise impact. We will also produce a policy briefing note entitled "Sustainable lowland peat management: a future roadmap". See also the letters of support for this project provided by DEFRA and DECC.

WIDER COMMUNITY: A web page and Twitter feed from the Bangor website will provide ongoing information on the project and its results. Different aspects of the project will be used for teaching, generating student projects. We will also feature the project in School Science Week, using visualisation of lettuces in peat soils to stimulate wider discussion about agriculture (food security) and the environment. Alongside regular publicity activities, we will also write news articles for the Soil Security website and for media outlets such as The Conversation.

SCIENTIFIC COMMUNITY: Our research will inform scientists working in several areas of research (e.g. crop production/agronomy, life cycle assessment, greenhouse gas emissions, soil quality). We will generate fundamental information on the C and N cycling in peat soils, ways to reduce their loss while still maintaining productivity and the socioeconomic costs associated with this. These findings will be promoted through the project-dedicated website, at national and international conferences and in peer-reviewed publications.
 
Description In the UK, fertile fen peatlands occur mainly in lowland areas of England, where they had an original extent of around 290,000 ha (Natural England, 2010). Since the initiation of large-scale pumped drainage of these areas in the 17th century, an estimated 90% of the original area has been converted to cropland or grasslands (Evans et al., unpublished), leading to widespread C loss and peat 'wastage', to the extent that around two thirds of the original lowland fen extent now has less than 40 cm of peat remaining (Natural England, 2010). A recent estimate of the ongoing soil loss rate from remaining areas of deep peat under arable cultivation is about 1.1-1.5 cm yr-1 during 1982-2004 (Dawson et al., 2010). Depending on peat properties and climatic conditions, between 35%-100% of peat subsidence is associated with oxidation, leading to high CO2 emission (Leifeld et al., 2011). At a global scale, this oxidation of cultivated peatlands is estimated to generate around 0.9 Gt CO2-eq yr-1, representing 2.5% of all anthropogenic GHG emissions (IPCC, 2013). Given this major contribution to global temperature forcing, there is an urgent need to develop more timely and appropriate management regimes in order to reduce drainage-induced peatland loss and contributions to atmospheric GHG concentrations.
Aims and Objectives: In this project, we hypothesise that active annual and seasonal management of the water table combined with other management interventions (e.g. winter cover crops, nitrification inhibitors and soil physical stabilisation agents) can be used to provide a cost-effective and practical solution to minimise soil loss and promote greater sustainability in these high value farming systems.
Aligned to this, the specific aims and objectives of our project are to:
1. Quantify the potential synergies between altering the hydrological regime with other agronomic management interventions to reduce GHG emissions. ? (Study 1 and 2)
2. Determine the short- and long-term relationship of water table depth with greenhouse gas (GHG) emissions and lettuce yield from cultivated lowland peatlands. ? (Study 3)
3. Investigate the environmental opportunities associated with adopting alternative land use for lowland peats ? (Study 4)
4. Understand the mechanisms underlying the widely divergent biogeochemical functions of soil moisture on peat soils, in order to reliably quantify associated feedback effects, and their impact on land use and climate change and land degradation ? (Study 5 and 6)

Study 1. Effective use of winter cover crops and water table management to reduce greenhouse gas emissions from cultivated peat soils
Abstract
Drainage and cultivation has turned peatlands from carbon (C) sinks into hotspots for greenhouse gas (GHG) emissions. Raising the water table and planting of winter cover crops are potential strategies to help reduce peat oxidation and re-initiate net C accumulation during the non-cropping period. However, the effects of these practices as well as their interactions on GHG emissions remain unclear. Here, we carried out an outdoor mesocosm experiment to elucidate the effect of water table depths (-30 cm and -50 cm) and winter cover crop cultivation (vetch, rye, no plant) on carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) fluxes during winter period (November-April). Measurements were made of soil-atmosphere GHG exchange, GHG concentrations within the peat profile and soil water solute concentrations. Our results showed that high water table significantly reduced ecosystem respiration, while it had no net effect on N2O and CH4 fluxes. Uptake of available N by the cover crop significantly reduced nitrate in soil solution, thereby lowering the potential for leaching and both direct and indirect N2O emissions. No interactive effects between water table and cover crops were detected for any of the measured GHG fluxes. Seasonal variations of GHG fluxes were positively correlated with soil air concentrations at -15 cm and -40 cm depths, which were further regulated by dissolved organic C, nitrate concentration as well as anaerobic conditions in the soil. We conclude that raising water tables, combined with the cultivation of some cover crops, could significantly reduce GHG emissions. Consequently, these strategies could be considered as a practical way to reduce peat oxidation and mitigate GHG emissions in cultivated peatlands outside the main cropping period.

Study 2. Rye cover crop incorporation and high water table mitigate greenhouse gas emissions in cultivated peatland
Abstract
Drainage and cultivation of peat soils almost always result in rapid soil degradation and a loss of soil organic matter (SOM). This loss of soil quality is largely due to the introduction of oxygen into the soil which accelerates microbial activity and breakdown of the peat substrate. Winter cover crop cultivation and subsequent incorporation as a green manure may provide a mechanism to both restore SOM levels while simultaneously reducing the need for mineral fertilization and reducing erosion risk. Similarly, raising the water table in the winter to reduce oxygen levels may also slow rates of SOM loss. However, the combined effect of residue incorporation and water table management on greenhouse gas (GHG) emissions in these highly productive peat soils remains unknown. In the present study, two cover crops (vetch and rye) with contrasting carbon/nitrogen (C/N) ratios were incorporated into peat soils as green manure at two water table depths (-50 and -30 cm). Both vetch and rye incorporation increased CO2 emissions due to labile C addition and removal of N constraints. However, the two cover crops had strongly contrasting effects on N2O emissions. Incorporation of low C/N ratio vetch stimulated N2O emissions whilst high C/N ratio rye decreased N2O emissions. Raising the water table decreased CO2 emissions by inhibiting SOM mineralization, but increased N2O emissions by stimulating denitrification. CH4 fluxes were not affected by water table depth, and their contribution to total global warming potential (GWP) was negligible. Therefore, we conclude that high C/N ratio cover crops (e.g. rye) in combination with a raised water table represent viable management options to improve soil quality and mitigate GHG fluxes.


Study 3. Effect of water table management on greenhouse gas emissions and lettuce productivity in cultivated peatland
Abstract
Lowland peatland is the most productive agriculture land; however, arable production on lowland peat is inherently unsustainable. A large proportion of the UK's horticultural farming takes place on drained lowland peatlands, turning them from C sinks into hotspots for greenhouse gas (GHG) emissions. This study was design to investigate whether water table management could reduce GHGs emissions from agricultural peatlands, while simultaneously maintaining the current levels of horticultural productivity. Sixteen intact cores were subjected to two water table treatments (-50 cm and -30 cm depth) from October 2017, and partly changed water table after 7 months. In middle of June, one lettuce was planted in each core. Measurements were made of soil-atmosphere GHG exchange, GHG concentration within the peat profile and soil water solute concentrations. In this study, water table raising significantly reduced ecosystem respiration, while it had no effect on CH4 flux. Meanwhile, soil N2O flux was lower under high water table than under high water table. Unexpectedly, water table change did not produce GHG pulse as expected, likely attributed to (1) low temperature; (2) low NO3- concentration; or/and (3) low measurement frequency. Overall, long- or short-term water table raising (e.g. High-High, High-Low and Low-High treatments) significantly decreased GHG budget. However, high water table significantly decreased yield of lettuce, while yield under High-Low and Low-High treatments did not significantly differ with either Low-Low or High-High treatments.


Study 4. The effect of water table depth on sheep urine patch N2O emissions
Abstract
In the last century, 10%-20% of the original peatland area worldwide has been drained for agricultural use, turning them from C sinks into hotspots for greenhouse gas (GHG) emissions. A recent estimate of the ongoing soil loss rate from remaining areas of deep peat under arable cultivation is about 1.1-1.5 cm yr-1 during 1982-2004. To protect the peat soil from further loss, land use change has been considered as an option to improve soil quality and decrease GHG emissions in drained and cultivated peatlands, as soil C accumulation could be made when agricultural lands are converted to grasslands. If the conversion happen, the large numbers of livestock grazing on grassland, will be identified as a potentially large source of nitrous oxide (N2O) via excretal deposition on nitrogen to the soil. With a radiative forcing of ca. 296 times that of CO2 and its contribution to the depletion of stratospheric ozone, N2O is an important GHG associated with livestock production. Here, we conducted a mesocosm study to explore the effect of water table depths (-10 cm, -30 cm and -50 cm) and with/without sheep urine patch on carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) fluxes. Measurements were made of soil-atmosphere GHG exchange, GHG concentrations within the peat profile and soil water solute concentrations. Data is waiting for analysis.

Study 5. Microbial utilization of low molecular weight organic substrates in cultivated peats responds to soil warming and degradation
Abstract
Peatlands represent one third of soil carbon (C) in the terrestrial biosphere. However, this C can become destabilized in response to climate warming and soil degradation. It is therefore important to understand mineralisation and carbon use efficiency (CUE) of low molecular weight organic substrates (LMWOS) and how these respond to temperature and nutrient availability. We incubated non-degraded and degraded peat soils under increasing temperatures (4, 10, 20, and 30 oC). Either 14C-labelled glucose or amino acids was added to measure microbial utilization of LMWOS. The total loss of 14CO2 from soil increased significantly with increasing temperature, regardless of peat soil degradation. Warming altered the dynamics of LMWOS decomposition by increasing C allocation into the fast pool and also accelerating the turnover of the slow pool. The half-life of LMWOS decreased more than 50% when temperature increased from 4 to 30 oC for both substrates. CUE was always higher for degraded than non-degraded peat soil and both declined by 0.002-0.005 oC-1 with temperature increase. Peat degradation decreased LMWOS-C allocation into the rapidly respired pool, but had no effect on pool turnover rate. Increased temperatures reduce the difference in CUE of glucose between non-degraded and degraded peat soils, but enlarge the difference in CUE of amino acid, at least in the short-term. Our work suggests that climate warming could accelerate the C mineralisation and turnover in peat soil and larger effects would be expected in non-degraded soil. This study provides an important initial step in characterizing the response of the microbial utilization of labile C to temperature change and soil degradation in cultivated peatlands.

Study 6. Interactive effects of moisture and iron on the stability of carbon in peatlands: 'enzyme latch' or 'iron gate'?
Abstract
Peatlands represent the largest natural terrestrial carbon (C) store, however, this C can become destabilized, particularly in response to anthropogenic disturbance or lowering of the water table. Several conflicting paradigms have been proposed to explain the positive or negative relationships of moisture status with C loss rates in peat soils (e.g. 'enzyme latch', 'iron gate'). The relative importance of these regulatory mechanisms and whether they are mutually exclusive, however, remains unknown. To address this, our aim was to evaluate the effects of contrasting soil moisture regime and addition of Fe(II) on organic matter mineralization in an agriculturally managed lowland fen peat. Our results showed that for the first 50 days of incubation, phenol oxidase activity under saturated conditions (120% water holding capacity; WHC) was lower than that at 65% WHC, but after this period the pattern was reversed. These results suggest that two contrasting mechanisms may control phenol oxidase activity and soil organic carbon (SOC) mineralization simultaneously, with the dominant controlling factor and final response being dependent on the trade-offs between oxygen and Fe(II) effects. Although Fe(II) addition increased phenol oxidase activity, it suppressed SOC mineralization regardless of the soil moisture content, suggesting that iron can protect soil C from microbial decomposition in lowland peat soils. Our study has implications for understanding the widely divergent biogeochemical functions of soil moisture on peat soils and emphasizes the influence of oxygen and Fe(II) on phenol oxidase activity and SOC mineralization.


References
Dawson, Q., Kechavarzi, C., Leeds-Harrison, P.B., Burton, R.G.O., 2010. Subsidence and degradation of agricultural peatlands in the Fenlands of Norfolk, UK. Geoderma 154, 181-187.
IPCC, 2013. Working Group I Contribution to the IPCC Fifth Assessment Report, Climate Change 2013: The Physical Science Basis. Cambridge University Press, Cambridge, UK.
Leifeld, J., Müller, M., Fuhrer, J., 2011. Peatland subsidence and carbon loss from drained temperate fens. Soil Use and Management 27, 170-176.
Natural England, 2010. England's peatlands: carbon storage and greenhouse gases (NE257). http://publications.naturalengland.org.uk/publication/30021
Exploitation Route Looking at adoption by horticultural growers. Defra using for policy guidance.
Sectors Agriculture, Food and Drink,Environment

URL https://www.soilsecurity.org/seflos/
 
Description helping DEFRA with peatland policy
Geographic Reach National 
Policy Influence Type Participation in a national consultation
Impact helping guide national policy to reduce peat loss in horticulture
 
Description SARIC
Amount £283,012 (GBP)
Funding ID NE/R017425/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 10/2018 
End 09/2020
 
Description STARS CDT Case Partner
Amount £6,000 (GBP)
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 09/2017 
End 08/2021
 
Description Collaboration with G's and G's growers 
Organisation G's
Country United Kingdom 
Sector Private 
PI Contribution Interactive research progamme on their fields in East Anglia
Collaborator Contribution Guidance in research and practical outcomes. Supply of data
Impact CASE funded studensthip
Start Year 2017
 
Description Open Farm Sunday 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Open Farm Sunday. We had a big demonstration of the N sensor field trials and soil security
Year(s) Of Engagement Activity 2018
 
Description Peatland policy workshop 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Policymakers/politicians
Results and Impact 20 people attended the policy workshop to look at the future roadmap for lowland peatlands
Year(s) Of Engagement Activity 2019
 
Description Radio interview 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Radio interview on soils on Radio Wales
Year(s) Of Engagement Activity 2020
 
Description industry meeting on mitigation options 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Industry/Business
Results and Impact Providing advice to industry on the best way to mitigate greenhouse gas emissions from lowland peat soils.
Year(s) Of Engagement Activity 2018
 
Description soil security conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact Soil Security fnal workshop meeting
Year(s) Of Engagement Activity 2019