Wildlife and our food

As a society, we have become disconnected, not just from the sources of our food, but from the very concept that the process of food production is integrated with countless wildlife species. In Chapter 3 of Farming with the Environment, I describe the results of our research into the role of life in soil that is used to grow food. Chapter 4 extends this to above ground wildlife – pollinating insects, crop pest predators, and other species that have evolved over millennia to share the farmed environment with us.

Thirty years of wildlife monitoring provide exceptional data for the Allerton Project’s farm at Loddington. We have also carried out research into habitat use by a wide range of species, including grass, hedge and woodland field boundary habitat use by crop pest predators such as spiders, and ground and rove beetles.

Our work on pollinating insects has revealed how their abundance today is limiting fruit-set in hedgerow shrubs such as blackthorn and hawthorn, and landscape scale surveys provide an insight into the enormous range in abundance of wild bees across a range of sites. We have used spatial models to estimate how wild bee numbers might have changed historically, but more importantly, how their numbers could be restored through future land use change.

Six species of grasshoppers and crickets have colonised the farm, largely in response to climate change, during the first fifteen years of the project. Despite national declines in abundance of moths, our long-term monitoring shows that moth numbers have increased by more than a third at Loddington over the thirty years, with the number of species present also increasing by around 20%. Overall songbird numbers doubled within the first six years of the project and much of our research over the years has been on how songbirds use the land we are managing to produce food.

For example, song thrush nests that successfully produce young have a higher proportion of pasture grazed by sheep within their foraging range than failed nests which have more arable land. Yellowhammers change from one crop to another through the nesting season when gathering food for their young, so crop diversity within the foraging range is likely to increase survival. We also have detailed information of the diet of many birds that forage for invertebrates on productive land during the breeding season.

Our research has shown that the land that we are managing to produce food is not just supporting wildlife, but that in some cases those species are increasing in abundance, many are beneficial to food production, while others are iconic species that we appreciate in their own right. Developing methods of further improving the farmed environment to benefit this full range of species is the subject of another chapter.

Soil - the life support system

It is right that soil should be the subject of an early chapter in my recently published book, Farming with the Environment – Thirty Years of Allerton Project Research. The health of our soil literally and metaphorically underlies the ecosystem on which we all depend. Not least, it is fundamental to farming.

Almost by definition, soil health is dependent on biological activity and much of our research over the years has focused on life in the soil, the role it performs, and the influences on it. Earthworms, collembola and microbial fungal and bacterial communities all perform important functions, and the soil also supports larval and pupal stages of many invertebrates that are predators or parasitoids of crop pests.

We have found that physical properties, especially compaction of our clay soils, reduce biological activity and abundance of some earthworms and other invertebrates. We have demonstrated that compaction limits water infiltration rates, contributing to surface runoff and loss of soil and nutrients to water. Using our Gasmet multi-gas analyser, we have found that emissions of nitrous oxide, a greenhouse gas with three hundred times the global warming potential of carbon dioxide, are substantially higher from compacted soils than well-structured direct drilled land. In a direct drilled system, sub-soiling alleviates this problem without the negative impacts on soil function associated with the more traditional approach of ploughing.

Soil organic carbon also influences soil biology and water infiltration rates. Comparing plough and direct drilled plots, our research reveals that microbial activity and diversity, and associated CO2 emissions are higher in the latter but that direct drilled plots are also associated with higher soil carbon. We are continuing to explore this apparent anomaly. We have also explored the influence of reduced cultivations on surface runoff and loss of sediment and nutrients from arable land.

We have found that cover crops intended to reduce soil and nutrient loss before spring crops can have some benefits in supressing weeds and encouraging earthworms, with subsequent benefits to cropping, but only where cover crop establishment is really good, and this can be challenging on clay soils. If not managed too intensively, some modern deep-rooting grass cultivars have the potential to sequester carbon in a stable form below the plough layer, and to increase water infiltration rates, contributing to catchment scale targets for water quality and flood risk management.

Such wider benefits, extending far beyond the soil at the field scale, also include positive contributions to terrestrial biodiversity within farming systems, a topic covered in the next chapter of the book.

The Long View

This is the first of a sequence of blog posts based on chapters from my latest book, ‘Farming with the Environment: Thirty Years of Allerton Project Research’ which was recently published by Routledge. Logically enough, I am starting at the beginning, not the beginning of the Allerton Project, but the earliest evidence we have for agricultural activity on the farm at Loddington in Leicestershire.

Archaeological fieldwalking has revealed the presence of Neolithic flint scatters, Iron Age iron smelting, Roman farmsteads, and a small Anglo-Saxon settlement. The size of the village at Loddington grew during the Medieval period, only to contract again as a result of plague. Then the Medieval open field farming system gave way to enclosed fields for grazing livestock, with only limited arable production until the Second World War threatened national food security.

The subsequent period has seen a radical change in food production, and in wider society. The science-led Green Revolution was associated with a move towards high external input agricultural systems, simplification of crop rotations, and an increase in scale. The negative impacts of this on the environment, and an increasing realisation that agricultural and environmental objectives are integrated, inspired a move towards agri-environmental research. It is worth considering how past farmers would regard our current farming methods and how future generations will judge their sustainability. The GWCT’s pioneering ecological studies, and the wide-ranging research at Loddington have been at the heart of efforts to ensure that agricultural and environmental objectives are met simultaneously.

Members of the local farming community who remember the farming systems of the 1930s have contributed verbatim to the book. They bring to life the practices adopted at the time. Understanding the evolution of farming systems through history provides an enlightening context against which to consider how food might be produced in future. Such historical knowledge also strengthens local identity, establishing ownership of current agri-environmental problems and opportunities for change.

Knowledge of how wildlife has responded to historical changes in land use is much more sketchy than the knowledge of land use changes themselves. Systematic records of wildlife have been kept only in recent decades, supplemented by more casual observations from the late nineteenth and early twentieth century. Together, these provide an insight into the changing fortunes of a range of species in response to both land use change and other factors.

Pollen records provide evidence of longer-term ecological change, and we have also used our understanding of current ecological processes to make a tentative estimation of previous aquatic invertebrate and wild bee communities for example.

But for most of us, the wildlife we experienced in our childhood provides a subconscious benchmark against which to assess the current status of wildlife species, and more worryingly, our aspirations for future change. Understanding longer-term historical changes in land use and species abundance provides essential context for developing plans for increasing wildlife, alongside the maintenance of food production, but a scientific understanding of how these are integrated is vital. That is the subject of subsequent chapters in the book.

The Allerton Project research book is published today!

‘Farming with the Environment: Thirty Years of Allerton Project Research’ is published today.

The book is a detailed but accessible account of the wide range of agri-environmental research that we have carried out since the project started in 1992. Topics covered include farmland ecology, the design of new management practices to enhance farmland wildlife, soil management and health, catchment management, and water quality and ecology and much more. One chapter explores land management issues from the farmer and farm business perspective. Another draws on our research work to emphasise the need to understand and accept the complexity of many of the issues in order to make meaningful changes that will meet both farming and environmental objectives. The practical and policy implications of our research form a strong theme for the book.

We have achieved much in the 30 years of the Allerton Project's research activities. In recent years, songbird breeding numbers have consistently been around 90% higher than in the 1992 baseline. In the intervening years, numbers have fluctuated in response to our changes in management, providing valuable information on how different species are affected by different management practices. We have made a major contribution to the suite of habitat management options available to farmers through agri-environment schemes, particularly wild bird seed crops, supplementary feeding, grass margins and beetle banks. Our research has taught us much about how best to manage soils to achieve multiple benefits, and about the management of water at the catchment scale.

The research described in the book has been carried out by our own research staff on the farm at Loddington, by other GWCT researchers, by several PhD students, and numerous research partners from other organisations. While all these people are too numerous to mention individually in the book, beyond citation of their respective contributions, our current small research team at Loddington is represented by John Szczur, Jenny Bussell Gemma Fox and myself.

John Szczur is our Ecologist and has been with the Allerton Project since it started in 1992. He has an exceptional knowledge of plant, vertebrate and invertebrate identification and ecology and carries out a lot of the wildlife survey work at and around Loddington, as well as much of the sample and data collection for our Water Friendly Farming project. Dr Jenny Bussell is our Soil Scientist and has considerable experience of soil function and greenhouse gas flux in a wide range of natural and agricultural systems across the UK and abroad. She joined us in 2019. Gemma Fox has been our Research Assistant since 2017 and has previous experience as an Animal Health Inspector as well as considerable personal experience of beef and sheep farming. She collects much of the data associated with our soil and livestock research.

Our combined expertise forms a core around which we have assembled a considerable network of research partners to enable us to carry out wide-ranging interdisciplinary research. The publication of our book enables us to make this work accessible to a wide audience to inform management practice on-farm, and national land use policy.

Farming with the environment

Thirty years ago today, I drove from my then home in Hampshire to Loddington in Leicestershire to conduct a night-time spotlight count of brown hares. That was the start of thirty years of data collection on what was to become the Allerton Project research and demonstration farm.

The breadth of our research over the past thirty years has been possible through collaboration with researchers from other organisations and universities, as well as the expertise of the Allerton Project’s own staff. Multiple collaborations over the years have brought specialist expertise that has enabled us to cover topics as diverse as aquatic ecology, water quality, flood risk management, soil management and biology, carbon sequestration, ruminant nutrition, greenhouse gas emissions, agroforestry, game management, farmland ecology, pollinators and crop pest predators. This interdisciplinary approach has also extended into the social sciences and economics, recognising the multiple influences on farmers’ decision making.

All this work is described in my forthcoming book, covering the thirty years of research at the Allerton Project. Publication of the book comes during a period of considerable change in the way food is produced and agricultural land is managed, not only in the UK, but across much of Europe, North America and other parts of the globe. This is an appropriate time to share our learning to inform this process.

Allerton Project songbird numbers

As farmers across the country focus their attention on the Big Farmland Bird Count it’s time to reflect on how songbird numbers on our own farm have changed since the Allerton Project started thirty years ago. Overall numbers of breeding songbirds doubled in the first seven years of the project in response to management by our gamekeeper at the time, Malcolm Brockless, comprising habitat management, winter feeding and predator control. This was a remarkable achievement against the context of continuing declines across the country.

We monitor bird numbers using a combination of annual transects which provide an estimate of relative abundance, and a detailed census of all breeding birds which we carry out every five or six years. Despite removing many of the beneficial management practices for research purposes in the second decade of the project, causing bird numbers to drop, our recent transects reveal that songbird numbers have bounced back and in 2021 were 91% above the 1992 baseline year.

The detailed territory mapping is particularly useful for assessing numbers of the less numerous species and the data from the 2021 territory mapping are just in. As indicated by the transect data for overall songbird abundance, the territory mapping data reveal that many species have increased substantially, but not all have done so.

Recent population changes for long-term nationally declining songbird species (Allerton Project and BTO BBS data).

It is particularly interesting to consider the species that declined nationally between the 1970s and 1990s and are ‘red-listed’ as a cause for conservation concern. Some of these have subsequently increased slightly nationally, and regionally in the East Midlands (based on BTO data), while others have experienced slight continuing declines. Those species that have increased slightly in the East Midlands have increased very substantially at Loddington, while skylark and yellowhammer which have declined slightly in the region, have not increased at Loddington.

It is gratifying to record the considerable conservation success for species such as song thrush, dunnock, bullfinch, linnet and reed bunting. As well as increasing numbers at Loddington, improved adult survival and breeding success may be contributing to the wider population of these species through dispersal from the farm. This may even be the case for skylark and yellowhammer. Much of our management is known to benefit these species, along with others, and it is possible that abandoned territories in the area around Loddington are being occupied by birds dispersing from the farm rather than remaining on it to swell the breeding numbers. We cannot know for sure, but it is good to report that songbird numbers at Loddington are very considerably higher than they were when we took the farm on thirty years ago.

Deep-rooting grass cultivars could contribute to flood risk management

Introducing grass leys into arable rotations has the potential to improve soil structure and organic matter. This has benefits to the arable rotation, but can also increase water infiltration rates during storms, with resulting benefits in terms of flood risk management at the catchment scale. Reduced runoff from agricultural catchments can also result in improved water quality and aquatic ecology.

In one of our replicated plot experiments in the EU funded SoilCare project, we selected five modern deep-rooting agricultural grass cultivars as being the most likely to create pathways for water to reach deep into the soil profile, rather than running off the surface. Each cultivar was represented as a 50% component of an otherwise standard ryegrass and clover mix, with control plots comprising this standard mixture alone. The whole area was grazed by sheep and cut for silage following standard practice, but in years three and four of the experiment, we fenced off a three metre wide strip which was ungrazed and uncut.

We found that water infiltration rates were highest for the Festulolium cultivar, 'Fojtan' and the cocksfoot cultivar, 'Donata' in Year 1 of the experiment, but this was not repeated in subsequent years. A detailed assessment of root volume through the soil profile in Year 3 revealed that Fojtan root biomass was nearly four times higher than the standard ryegrass mixture at 70cm, but this was the case only where there was no grazing or cutting. In the adjacent cut and grazed areas, the standard ryegrass mixture had higher biomass at 70cm, but this was only half that of the ungrazed Fojtan. In Year 4, when root volume for all five cultivars was measured, four of them had higher values in ungrazed areas than grazed areas, but this difference was not statistically significant.

Soil compaction at 10cm was significantly higher in the grazed and cut areas than the fenced off portions of the strips, and within the fenced off area there was a 40% difference in sward volume between the areas with highest and lowest compaction. As root volume reflects above ground biomass, compaction is likely to be limiting water infiltration both directly, and by limiting root growth.

The results suggest that while some deep-rooting grass cultivars have the potential to contribute to landscape scale flood risk management, their capacity to do so may be limited by soil compaction associated with grazing livestock and harvesting of silage. As autumns become increasingly wet, grazing during this period can be particularly damaging to soil structure. For objectives such as flood risk management and water quality improvement to be met, a balance may need to be struck between the management adopted to meet the objectives of farm businesses and those of wider society. Economic incentives within the new Sustainable Farming Initiative to increase sward height and manage stocking densities to minimise poaching and soil compaction may enable farmers to meet both objectives if the right balance can be struck between payments and practice on different soil types.

There are more details of our research in: Stoate, C., Bussell, J. and Fox, G. 2021. Potential of deep-rooting agricultural grass cultivars for increasing water infiltration and soil organic carbon. In: Intercropping for Sustainability: Research developments and their application. Aspects of Applied Biology 146.

Soil moisture and management

Understanding soil moisture is important to improve the effectiveness of cultivations. Wet soil is prone to compaction, but soil moisture is important to soil cohesion, maintaining channel shape at depth when mole ploughing. To reduce damage to soil structure during feld operations, soil should be dry on the surface. Dry soil is also more friable, breaking down easily to produce cracking at the required depth during subsoiling. With help from Agrii, we have been using soil moisture sensors to help understand how the data generated might inform decisions about timing of field operations at different depths in the soil profle.

You can download a pdf summarising our results here.

 

Feeding willow to ruminants could reduce greenhouse gas emissions

Trees provide shelter and shade for livestock, and some offer additional forage.  In 2019, we were one of three research sites which contributed to a study of the potential of goat willow, oak and alder leaves as a source of supplementary minerals.  Willow was consistently higher in zinc and cobalt which is often deficient in grass and is important for the synthesis of vitamin B12. If you have not seen it, you can find the summary here.

In 2019, we also carried out an experiment with Nottingham University School of Veterinary Science in which willow leaves were fed to weaned lambs to determine whether the higher cobalt in leaves was reflected in higher concentrations in the animals.  Blood samples taken before and after feeding willow for a two-week period confirmed that blood cobalt concentrations and vitamin B12 were significantly higher in willow-fed lambs.

Lambs feeding on willow leaves at Loddington

Condensed tannins in willow leaves have the potential to supress microbial activity in the rumen, reducing uptake of nitrogen into the blood, and ultimately into urine.  This has the potential to reduce emissions of nitrogenous gases, primarily nitrous oxide and ammonia from urine patches.  Inhibition of microbial activity in the soil could have the same effect.  As nitrous oxide is a major greenhouse gas, and ammonia has negative air quality implications, the use of willow to reduce these gaseous emissions from urine could potentially contribute to climate change and human health targets.

In August 2020, we fed 200g of goat willow leaves per day to two groups of six weaned lambs over a two-week period.  Another two groups of six lambs were not fed willow.   At the end of the experiment, we identified fresh urine patches by direct observation of the lambs (six willow-fed, and six not willow-fed) and used our Gasmet gas analyser to measure emissions of carbon dioxide, as well as nitrous oxide and ammonia.  We did this within 20 minutes of urination, and again one and two weeks later.

There was a consistent trend for urine patches in pens with lambs that were fed willow to have lower emissions than those that were not fed willow for each of the three gases, although this was only statistically significant for nitrous oxide in Week 2, probably because of the small number of urine patches sampled.  Ammonia emissions declined rapidly, nitrous oxide emissions were mainly in Week 2, and carbon dioxide emissions declined gradually over the two-week period.  Lower carbon dioxide emission suggests that microbial activity was supressed in the soil, rather than in the rumen, but we cannot discount a contribution from the latter.  Willow is well suited to mechanical harvesting, or to direct browsing of coppiced trees if livestock access is managed to ensure sustainability, and our results suggest that feeding willow to ruminants could contribute to climate change and air quality targets.

 

Stoate, C., Fox, G., Bussell., J. & Kendall, N.R. 2021. A role for agroforestry in reducing ammonia and greenhouse gas emissions from ruminant livestock systems. Aspects of Applied Biology 146.

Managing headwater catchments to reduce downstream flood risk

There is increasing concern about flood risk associated with climate change, and an interest in means of addressing this that complement traditional flood defence measures in flood-prone areas.  Since 2016, we have been installing permeable timber dams in the Eye Brook headwater within our Water Friendly Farming project.  The intention has been to create low cost barriers to hold water back in ditches and small streams, without any negative consequences for farming, so as to reduce downstream risks of flooding.  Most of the dams are designed to hold water back within the channel, but some are extended into small floodplains to increase the storage capacity where the land is otherwise unproductive from an agricultural perspective, or not used for access.

Initially, these dams were made with lengths of cordwood sourced from local woods that were being thinned to improve timber production or wildlife habitat.  They were intended to be easily constructed by a local contractor or farmer.  Although we wanted to hold water back during storm events, we did not want to impede baseflow so a gap was left at the base of the dam.

The dams worked well until the really heavy storms arrived and six of the dams on the main stream were badly damaged.  As a result, we redesigned and rebuilt these larger dams so that they were made from long lengths of timber that spanned the whole channel width, without the need for joins or in-channel support posts.  We selected larch to prolong the life of the dams.

We also raised the base of the dams so that they were above winter baseflow.  This reduced the frequency with which water backed up behind the dams, but improved their performance during the larger events which are the ones we are most concerned about in terms of flood risk.  These dams have held up well to the largest storms and the flow monitoring at the base of the catchment allows us to evaluate their performance. With our partners at the Freshwater Habitats Trust, we have produced a guidance document on the practical design and installation of permeable dams which is available as a pdf here.

York University's hydrological modelling reveals that for the most commonly occurring storm events (those occurring at up to one in a hundred-year intervals), the 28 dams across the 1,000ha catchment reduced peak flow at the base of the headwater catchment by 19-24%.

For very severe events (those occurring only once in a thousand years), the reduction in peak flow was 11%.  Although encouraging, this is a reminder that we are less able to adapt to the more severe events that climate change is expected to confront us with more frequently in future.  This is one of many reasons why, as well as investigating approaches to adaptation, our research is also focusing on ways in which we can mitigate climate change through the management of agricultural land.

Permeable dam outside the study area at our research and demonstration farm at Loddington

Soil and climate change research

It is hard to know how this summer will turn out.  An exceptionally wet autumn and winter completely prevented the establishment of autumn-sown crops at Loddington and other local farms.  There was just about time to drill spring varieties in those fields where we needed to do so for research, or considered that it would still be economically viable to do so for our farm business.  Then the drought hit.

By June, livestock farmers were searching around for additional grazing as pasture and leys withered, recalling memories of the prolonged drought just two years ago.  Social media were scattered with posts from normally successful arable farmers sharing images of drought stressed crops and professing that the continuing weather uncertainties and extremes were now making it impossible to maintain a viable business.  Recent rain has provided a reprieve by increasing surface soil moisture, at least for now.

Loddington soil moiture deficit to June 2020, including the 2018 drought and exceptionally wet autumn/winter of 2019/20

Our research aims to contribute to our understanding of this issue.  We want to see continuing economically viable food production on farms such as ours, to understand better how to reduce our greenhouse gas emissions and to sequester carbon in our soils.

Global warming potential of CO2 and N2O in compacted SoilCare project plots

Monitoring of greenhouse gas flux in compacted soils as part of our contribution to the EU-funded SoilCare project reveals that carbon dioxide flux is higher in ploughed plots than in direct drilled plots.  In these compacted conditions, nitrous oxide flux is higher in direct drilled plots.  The amounts involved are very low, but because nitrous oxide has a global warming potential that is nearly 300 times that of carbon dioxide, the implications for climate change are that much greater.  Looked at together, the global warming potential of greenhouse gases associated with ploughed and direct drilled plots is roughly equivalent.  The additional emissions associated with multiple field operations in the ploughed plots mean that direct drilling has the lower impact.

Mean Soil Organic Carbon from ten Water Friendly Farming project fields

Reduced soil disturbance, whether through direct drilling or other practices such as incorporation of leys into the rotation, also has the potential to increase soil organic carbon.  Data from local fields in the Water Friendly Farming project study area reveal that this is currently around 3%, and typically, declines with soil depth.  Increasing soil carbon helps to improve soil moisture retention during drought.  It also has the potential to deliver public benefits such as improved water infiltration during storms, resulting in better water quality and ecology, and reduced downstream flood risk.  At depth, stable forms of carbon represent an important potential carbon store, contributing to climate change mitigation.

Food, health and wildlife security

It is remarkable to think that the Covid-19 pandemic that is causing so much personal, political and economic disruption stems from a food market the other side of the globe.  Virus transmission from wild animals to people has highlighted the trade in wildlife for food in other parts of the world.  While the mode of transmission from wild species to people remains uncertain, there is clear evidence that this trade in species such as pangolins is unsustainable. The fact that such trade is now in the spotlight can only strengthen conservation efforts for these species, although this is dependent on secure income and food supplies for the people who would otherwise be doing the trading. The pandemic makes that more difficult to achieve.

Let's be clear though.  The justification for cessation of trade in endangered species for food is not that we find the consumption of wildlife culturally abhorrent. To follow that argument would lead us onto a slippery ethical slope.  It might also lead us to question the consumption of abundant species such as deer, rabbits and woodpigeons whose control is important to protect food crops and wildlife habitats in the UK, while also providing a source of food in their own right.

In fact, as well as reminding us of the moral imperative for conservation of our own wildlife species, food shortages associated with the pandemic have brought into question our food system and highlighted the need for domestic production at local, regional and national levels, alongside international trade.  The need to understand the relationship between food production and environmental objectives, including wildlife conservation, has never been greater.

Gemma Fox and team prepare for water infiltration assessments in our grass plots

Despite the national lockdown, our research into economically and environmentally sustainable farming methods continues, strictly within the constraints imposed by social distancing.  Where data collection requires more than one person to conduct fieldwork at the same time, we have been fortunate in being able to recruit other members of the same household to help out.

There have been numerous other challenges to overcome though.  With the implications for food producton of the 2018 drought still fresh in our minds, the intense rainfall over the most recent autumn and winter was exceptional. The very wet ground conditions completely precluded the establishment of autumn-sown crops, preventing food production from our land, creating economic problems for our farm business and for many others across the country, and leaving us with no arable experimental plots for research.  Fortunately, it has been possible to drill some spring-sown crops this month, albeit under difficult conditions.  Our research is increasingly focusing on these climate related challenges.

While potentially distracting from the over-riding need to address climate change, in common with climate change mitigation objectives, the Covid-19 pandemic highlights the need to act individually and collectively, locally and globally to address the challenges that affect us all.

New clean water ponds increase landscape scale aquatic biodiversity

We have just seen the publication of another journal paper from the Water Friendly Farming project, our collaborative project with the Freshwater Habitats Trust. The paper demonstrates for the first time the effect of creating new ponds on the number of aquatic plant species present in the landscape.

Creating new clean water ponds in low input pasture in 2013

Following discussions with land owners, we created twenty new ponds in one of our two 'treatment' catchments in 2013.  We selected sites very carefully so that the new ponds were in low input pasture or open areas of woodland where runoff into them was not affected by domestic or agricultural sources of nutrients. The selection of these non-productive areas also made the ponds aceptable to farmers; in fact the introduction of ponds onto farms was regarded as improving the landscape and creating additional interest.

Freshwater Habitats Trust researchers conducted a rigorous annual census of aquatic plants, not just in the new ponds but across multiple other small ponds, ditches and streams within the 3,000ha study area to provide a comprehensive understanding of the plant species present and their distribution across the various habitats.

Ponds generally proved to be a key habitat.  Adding our new clean water ponds brought substantial benefits: increasing total-catchment plant species richness by 26%, and the number of rare plant species by 181%. Populations of spatially restricted species also increased. Creating clean-water ponds specifically targeted for biodiversity could therefore hold considerable potential as a tool to help stem, and even reverse, ongoing declines in freshwater plant biodiversity across agricultural landscapes.

You can access our journal paper as a free pdf for a limited period here.

Integrating crop production at the catchment scale

Some research we carried out within the Water Friendly Farming project in 2017 has just been published in the Journal of Environmental Management.  We use a herbicide that is used to control black-grass in arable crops as an initial focus for exploring broad catchment management issues with farmers in the study area.

Propyzamide is applied to the oilseed rape stage of the rotation and while being a crucial means of controlling black-grass also creates a problem for drinking water supply as it often exceeds the 0.1µg/L limit set by the EU Drinking Water Directive.  This puts its use at risk of restriction.  The herbicide moves to water mainly adsorbed to soil particles, so as well as being linked to the stage of the crop rotation, its mobility is reduced by soil management practices that reduce erosion and subsequent sedimentation of water courses.

We found that the concentrations in water were influenced largely by the area of oilseed rape in the catchment, and by rainfall.  Modelling suggested that, to keep below the 0.1µg/L limit, the rape area would need to be restricted to just 2-3% of the catchment.  This is something that participating farmers felt was not practical to manage across the catchment, given that there were multiple farms and the rape area grown was up to 30% of the land area.  Oilseed rape was considered to be an important part of the rotation.  A higher limit for headwater catchments that are distant from drinking water abstraction points might be more manageable but would require coordination of, and collaboration between farmers.

Pest problems now make establishing rape more difficult

The farmers were more enthusiastic about the use of hybrid barley, a crop which supresses blackgrass, extends the rotation, and provides an early entry for a following rape crop.  Rape is the stage in the rotation which requires least soil disturbance and is often direct-drilled, with potential benefits to soil and water.  Reduced tillage and direct drilling reduce the risk of herbicide loss to water while also delivering other public benefits such as reduced sedimentation of watercourses, reduced nutrient concentrations in water, and enhanced aquatic biodiversity.  Farmers were also more generally accepting of reduced tillage and direct drilling for other stages in the rotation, but they identified practical constraints and economic barriers which prevented a wholesale switch to this system on our clay soils.

Since our research in 2017, oilseed rape has become a slightly less popular crop.  The ban on the use of neonicitinoid insecticides has made the control of cabbage stem flea beetle (a major pest of rape) a substantial challenge.  Alternative pyrethroid insecticides, applied as a spray to the crop, rather than as a seed dressing, reduce numbers of a wide range of other invertebrates, including beneficial predators and parasitoids of flea beetles.  It is especially important to encourage these beneficial invertebrates as flea beetles are developing resistance to pyrethroids.

The area of oilseed rape, its yields and profitability have therefore all declined in the past couple of years.  Up until that time, rapeseed and oil were imported and exported to and from the EU but the UK was essentially self-sufficient.  Reduced production in future could mean increased imports of vegetable oils from other countries.  If rape or sunflower are imported from the EU, the crops are currently subject to the same environmental standards as our own, but if from other countries we may find ourselves using oil and animal feed produced using methods which we would not permit in the UK, while simultaneously disadvantaging UK farmers.  Substitution with palm oil from Indonesia and Malaysia has even greater environmental implications.

The use of a herbicide and an insecticide in oilseed rape crops may seem to be independent activities to be considered in isolation, but our research on propyzamide, and the more recent developments with neonicitinoids demonstrate the integration of a wide range of associated activities across and beyond the production of the crop.

Our journal paper is available here as a free download until 18 March.