Megan Tresise is a third year PhD student in the School of Biology, and a Priestley Climate Scholar. Here, she shares insights from a recent secondment from her PhD to the Parliamentary Office of Science and Technology (POST) Fellowship and explores the key points raised in the POSTnote she co-authored.
Parliamentary Office of Science and Technology (POST) notes are four-page briefings used by parliamentarians as a summary of research evidence on a topical area. These briefings are used primarily by parliamentarians as a summary of research evidence on a topical area.
For three months between October and December 2021, I was given the chance to research and write my own POSTnote on Restoring Agricultural Soils through the N8 AgriFood funded POST Fellowship. This Fellowship has been one of the most interesting and career-inspiring opportunities presented to me during my PhD. I have gained skills that complement my professional development goals, which I hope will improve my current research and employability down the line.
This POSTnote is also the product of a highly topical area of both research and policy right now, with the Department for Environment Food & Rural Affairs (Defra) highlighting ambitions to manage all of England’s soils sustainably by 2030 and begin drafting a Soil Health Action Plan for England (SHAPE). This blog will explore the key points raised in the briefing, policy initiatives driving the need for soil research and where further evidence is needed.
Soils are fundamental to the food system, allowing us to raise livestock, grow crops and bioenergy sources. However, the complexity of soils extends further than food production, as there are numerous other services that soils provide, including water regulation, habitats for biodiversity, and climate regulation. These services are integrated with wider ecosystem functions, for example, water and nutrient cycling or carbon sequestration, making soil an invaluable, yet limited, resource. Soil Organic Matter (SOM) is the organic material left from decomposing plants and animals, Soil Organic Carbon (SOC) is the measurable carbon concentration of SOM. In agricultural systems, soil management aims to improve productivity and increase resilience to future climate impacts by building SOM. Conversely, intensive agricultural pressures on soil can reduce soil functionality and resilience through degradation.
Soil degradation from intensive management in the UK is thought to have caused 40% to 60% losses of soil organic carbon (SOC) on croplands, resulting in carbon dioxide (CO2) emissions. In England and Wales, soil erosion from wind and water affects almost 3 million tonnes of topsoil annually and almost 4 million hectares of agricultural land is at risk of compaction from heavy machinery and intensive grazing. Nutrients in soils are depleted under consistent cropping, leading to an increased need for artificial nutrient sources (e.g. nitrogen and phosphorous). Although evidence is currently limited, microplastic and microfibre pollution in soils from sewage sludge and plastic waste management is considered to be a growing concern for farm soils.
Changes in soil management practices on agricultural land could reverse soil degradation and alleviate pressures from climate impacts. Principles of regenerative, conservation and organic farming are increasingly used to restore soil functions. This style of soil stewardship puts emphasis on returning organic material to soils and building SOM, increasing soil cover, reducing disturbance and the use of agrochemicals (fertilisers and pesticides). Ongoing research seeks to understand the best soil management and restoration practices.
Fertilisers, synthetic and organic, provide essential nitrogen and carbon inputs to soils but when used in excess, can result in nitrous oxide (N2O) emissions. Soil additions of biochar, a charcoal-like product from burnt biomass, is being researched in a UK context, with previous research in the tropics suggesting yield improvements, reduced N2O and methane (CH4) emissions and soil carbon storage.
Conventional tillage of topsoil for cultivation (e.g. ploughing) aerates the soil and releases SOC as CO2. On the other hand, minimum or no till practices directly drill the seed into the soil, avoiding ploughing, and there is clear evidence that SOM and SOC are reduced under intensive, conventional tillage. No-till effectiveness is debated in a UK context due to the range of soil types and cool, moist climate limiting suitable areas for the practice to mostly clay soils.
Soil coverage year-round is beneficial for reducing erosion and organic material on the soil surface feeds the soil biology. Cover cropping between or within cultivations improves soil structure, nutrient cycling and carbon storage. Legumes fix nitrogen from the atmosphere, reducing the requirement for synthetic fertiliser. Grass leys have similar co-benefits and provide an addition to arable rotations to allow grazing livestock to deposit manures on the soil, increasing the nutrient content.
Soil policy and national monitoring efforts
Policy interest in soils has grown in the past decade. Key policy ambitions include the UK Government pledge to manage soils sustainably by 2030, as stated in the 25 Year Environment Plan, and more recently the Soil Health Action Plan for England (SHAPE). As the Common Agricultural Policy is phased out and replaced by Environmental Land Management (ELM) schemes, the new Sustainable Farming Incentive (SFI) is being developed. Land managers will be paid to protect and restore soil health through SOM testing and soil assessments under the new soil standards. Introductory levels will pay between £22 and £28 per hectare under the arable/horticultural soil standard and improved grassland soil standard, respectively. This increases to £40/ha and £58/ha at intermediate levels for the two standards. The SFI has been criticised for paying farmers for outcomes rather than practices, and it is unclear that the level of payment is enough to incentivise change.
In order to assess and pay land managers to protect soil, soil health indicators need to be selected. Given that there are over 700 soil types in England, it is difficult to select indicators relevant to all soils as they naturally vary in composition. Some of the key indicators that came out of the academic interviews were biological in nature, such as Essential Biodiversity Variables, and carbon (organic). National monitoring, reporting and verification of soil status has previously been limited, which has resulted in gaps in the data about soil condition. Newer modelling and remote sensing techniques are increasingly used to supplement direct measurements for a better picture of soil condition.
Soil risk uncertainties
Climate change is a particularly uncertain threat to agricultural soils, with suggestions of warmer, wetter winters and hotter, drier summers across England. Soils could be resilient to such threats and buffer future shocks through advancements in soil science and technology. Recent research and development has included:
- Electronic nose (e-Nose) detection of Volatile Organic Compound signals from the soil in response to changes in management
- Robotics and remote sensing to help land managers make informed management decisions and support precision agriculture
- Soil spectroscopy lab work and portable tools that can capture quick measurements of soil carbon and other characteristics
- Circular economy thinking around soils to reduce agricultural waste through recycling of by-products and re-purposing of waste soils (e.g. from construction) for agricultural use
- Interactions between soil, the soil microbiome and plants are increasingly well understood, enabling innovations such as crop breeding from ancient varieties to suppress emissions and increase fertiliser use efficiency
I’m now back to PhD life, settling back into greenhouse gas accounting on farmland and thesis writing, but with a successful Fellowship under my belt. I think this opportunity will become invaluable to me when it comes to applying for a job after my PhD as it has helped me to gain a better understanding of the research-policy interface and how scientific research is used to make policy decisions.
On a personal development level, it has helped me to improve my communication skills, time management and ability to research for purposes other than academic interest. I think I would enjoy a career that puts me at the research-policy interface, whether that be for the public or private sector; so that I can build upon the skills I’ve developed during the Fellowship. If the opportunity to do the POST Fellowship lands at your feet, I would highly recommend applying.
This blog was original published by the Global Food and Environment Institute