Monday, 26 November 2018

Understanding catchment management issues

Soil moisture is gradually increasing following the summer drought and we approach that time of year when arable farmers have to consider when to apply propyzamide to control black-grass in oilseed rape.  This is the herbicide that is considered to be the most effective at controlling this major arable weed, but timing is everything.  The temperature needs to be falling and the ground needs to be wet, but not too wet or there is an enhanced risk of runoff to water, mainly associated with eroded soil particles.  Once in water, the herbicide readily exceeds the 0.1µg/L limit for drinking water and is difficult for water companies to remove.  While the 0.1µg/L limit is contested on the basis of lacking scientific evidence for negative impacts on the environment or human health, the fact remains that this is the legal limit for drinking water supply.
  


There are linkages here between farmer objectives for productive and profitable crop production, water company objectives for reducing pesticides in water, and environmental objectives for the conservation of aquatic wildlife affected by sediment.  Compacted, poorly functioning soils have a negative impact on each of these.  Because sediment clogs drainage channels downstream, there are also implications for flood risk management.  The herbicide is at the centre of a web of interacting issues.


By using four years of herbicide concentration data from the study catchments in our Water Friendly Farming project, together with rainfall, stream flow, and crop area data, our partners at York University could estimate that, to keep the herbicide concentration below the 0. 1µg/L limit, we would need to restrict the oilseed rape area to less than 5% of the catchment area.  Additional or complementary mitigation options include extending the rotation with vigorous hybrid barley which can compete against black-grass, reducing tillage intensity, and monitoring soil moisture and compaction to guide herbicide applications and soil management to reduce runoff.

We put these options to the farmers in one of our study catchments.  In some years the oilseed rape area is around 5% of the catchment, but in others it is up to 30%.  It depends which part of each farm's rotation is within the catchment boundary in any one year.  How could land use be coordinated so that the 5% limit was not exceeded? The consensus was that it could not!  Such a restriction would impose too heavily on the economics of the farm business and create tensions between neighbouring farms who do not normally work together.  Multiple tenure arrangements between neighbouring farms complicate the issue, and as small farms are increasingly managed by contractors, this restricts long-term planning and makes timely operations more difficult.  There was also concern about the economic risks associated with adopting a no-tillage approach to reduce erosion on clay soils, and a lack of long-term government support for more sustainable soil management.

Introducing hybrid barley into the rotation was well received as a means of extending the rotation and controlling black-grass, a principle that has additional potential benefits for pest and disease control, and for farmland wildlife.  There was also interest amongst the farmers in improving understanding of compaction with a view to carefully targeted management that would reduce erosion and improve crop performance.  And while farmers were reluctant to collaborate, they agreed that there was an important coordination role for local trusted advisors.

Because of its adoption of rigorous science in a landscape scale practical setting, the Water Friendly Farming project provides an excellent platform for understanding constraints and opportunities for developing future land use policy and practice.  As a result of this recent exercise, we all have a better understanding of how a wide range of objectives interact, where the constraints are, and what potential opportunities we could explore to meet the multiple objectives we all have for agricultural landscapes. 

Tuesday, 28 August 2018

Climate change research

Straw being fed to local cattle in early August
Drought conditions through the summer turned grass fields brown and made supplementary feeding of livestock, especially cattle, a necessity.  In our local mixed farming area, various deals involving the transfer of straw from arable to livestock farms have taken place that would be unheard of in a normal year. Such a resolution is more difficult to reach outside mixed farming areas.  But for everyone, this year's drought raises concerns about what a 'normal' year might be in future and how to build resilience into farming systems.

Another consideration is the contribution that those different farming systems make to climate change through greenhouse gas emissions.  We explored this a while ago through a student project with Cranfield University, based on real input and production data from Loddington, and from three other local farms.  Energy use is a major driver for greenhouse gas emissions across arable and livestock systems, although grass based systems with lower growth rates and production tend to buck the trend because of higher methane emissions.  This issue is being addressed by our partners in the Sustainable Intensification research Platform's farm network at North Wyke and Henfaes, and some of our own most recent research into multiple benefits from grass leys will also contribute to this developing knowledge base.
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GHG emissions associated with local farming systems
In arable systems, especially if excluding legumes, energy use is a clear driver of greenhouse gas emissions.  Around 60% of these are associated with fertiliser use, but differences between farms result from different levels of field operation associated with tillage practice.  A no-till approach results in substantially lower carbon dioxide emissions than crop establishment approaches involving cultivation.  Our research has identified other benefits of a no-till approach, but it is difficult to adopt on clay soils, and there are concerns that reductions in carbon dioxide emissions associated with fewer machinery passes may be offset by higher nitrous oxide emissions associated with waterlogged soil.

GHG emissions associated with compaction alleviation
We are in the early stages of exploring this issue as part of the EU funded SoilCare project.  As part of our contribution to this project, we have set up a compaction alleviation experiment in which we compare the use of the plough and a low disturbance subsoiler for reducing soil compaction with direct drilling without any alleviation.  Our initial monitoring of greenhouse gas emissions in the spring suggested that there were higher nitrous oxide emissions from the no-till soil without compaction alleviation, and based on the CO2 equivalent for Global Warming Potential, this resulted in all treatments being comparable in terms of their impact.  We need to gather further data in the coming year to establish whether this is really the case in compacted ground, and to what extent it applies in other circumstances.

Tuesday, 24 July 2018

Monitoring greenhouse gases

We are experiencing an exceptional heatwave. Drought conditions are having severe impacts on arable crop yields and the forage available for livestock.  Equally exceptional weather conditions in the spring forced livestock farmers to house their animals and feed silage much later than normal and hay and silage production has been severely limited by the dry conditions this summer. Hay is already being fed to some animals because of the lack of grass for grazing.

Drought-stressed grass and clover ley
With little rain in May, and none through the whole of June and July, our soil moisture data from fields at Loddington reveal why arable crops and grass alike are suffering. While soil moisture levels near the soil surface always decline through June and July, this year, soil moisture at depth has also declined earlier, more rapidly and to a greater extent than previously.  These experiences are consistent with clmate change predictions made in the past, and with the current trend.  As well as being severely affected by climate change, agriculture currently accounts for about 10% of UK greenhouse gas emissions, but because other sectors are decreasing their emissions, the agricultural contribution could rise to 30% by 2030.  We need to understand these issues better at the farm and field scale.


Soil moisture at a series of depths in the soil profile in a wheat field at Loddington
The Allerton Project's research programme covers a very wide range of agri-environmental issues but I have been increasingly conscious of the need to improve our understanding of the impacts on and of climate change.  In 2015, I was able to introduce the purchase of state of the art greenhouse gas monitoring equipment into a bid for the EU funded soil management research project, SoilCare and we subsequently became the only research farm within the network of sixteen across Europe to be gathering GHG data for the project.  In achieving this, we have been very much aided by Falah Hamad who recently completed his PhD with us, gaining much valuable expertise in greenhouse gas monitoring in the process.

Falah Hamad gathering data from pasture for his PhD
In his PhD, Falah explored the relationship between soil physical properties and soil biology across a range of land uses. Amongst many other findings, he was able to demonstrate that carbon dioxide emissions are consistently higher from well structured biologically active soils than from compacted ground. Given that we are aiming for well structured soils to meet our many other objectives for crop production, catchment management and biodiversity conservation, we need to understand this relationship better, taking account of the wider context of inputs and field operations.

In the SoilCare project, our Soil Scientist, Felicity Crotty, takes this a stage further to investigate the emissions, not just of carbon dioxide, but of nitrous oxide, a gas with 298 times the global warming potential of carbon dioxide, and one that is often associated with compacted waterlogged soils.  Although we expect emissions of methane to be low, we will also monitor this gas as it has a global warming potential that is 25 times that of carbon dioxide. We are exploring these greenhouse gas emissions in relation to a range of management practices that are designed to improve soil structure and function in arable and grass systems.

We have in mind objectives for improving crop and grass production, but also delivering public benefits such as improved water quality and reduced flood risk.  Understanding greenhouse gas emissions will further enable us to explore the numerous trade-offs associated with land management practices that are adopted to address multiple issues such as these.  As is all too clear at the moment, understanding how we continue to develop our food production while reducing our contribution to climate change must be high on the agenda.

We are now applying the experience we have gained through our recent research to other research projects at Loddington and are developing our existing collaborations with other research organisations.  We will continue to encourage the active involvement of farmers and wider stakeholders in this process in order to understand the full practical and policy implications of our findings, and to guide future research.

Tuesday, 17 July 2018

Ponds for pollinators

Numerous options within agri-environment schemes provide an opportunity to encourage pollinating insects on farmland by creating diverse flower-rich areas where bees and other insects can forage. In our landscape scale catchment management experiment, 'Water Friendly Farming' creating ponds for wildlilfe or to act as sediment traps to protect areas downstream has inevitably left numerous areas of adjacent bare ground, ripe for the establishment of these pollinator habitats.

In recent summers, our Ecologist, John Szczur has been monitoring the use of these opportunistically created habitats by insects.  The results provide a valuable insight into the role of vegetaton associated with newly created ponds for insect conservation on farmland.


One of the first observations was that in small wetland features such as small widened ditches and associated earth dams, wildflower mixtures failed to estabish, or were rapidly out-competed by naturally occurring plants.  John's monitoring consequently concentrated on five larger ponds. He also surveyed nearby comparison sites which lacked ponds and newly created wildflower habitats.

Flies tended to dominate the insect community, making considerable use of Wild Carrot where this was available, but the focus of the study was on other pollinating insects comprising bumblebees, wasps, other Hymenoptera, butterflies and moths, beetles and true bugs.  The proportion of each of these varied between sites, but bumblebees and butterflies and moths tended to be the major groups.

At the pond sites, bumblebees were recorded mainly on Birdsfot Trefoil and Spear Thistle, but with a range of other plant species also being visited, and at the comparison sites, Spear Thistle was by far the main species used, with Hogweed, Great Willowherb and Bramble also being visited regularly.  Buterflies and moths used Creeping Thistle almost exclusively at the comparison sites, but around the ponds, made considerable use of Oxeye Daisy, Common Knapweed, Spear Thistle, Tufted Vetch, Birsdfoot Trefoil and Creeping Buttercup.

The number of flowering plant species was consistently higher at sites with ponds and sown margins than at comparison sites.  At two of the sites, pollinator abundance at pond sites was more than twice that at the comparison sites, but for the remaining three sites there was no difference in the number of pollinators present.

These observations highlight the importance to pollinating insects of naturally occurring plant species such as thistles and willowherbs, and ditches, whether modified to reduce agricultural impacts on water, or as standard features in agricultural landscapes, provide an abundant source of such plants.  Where there is more space to create new habitat, a greater range of sown plant species can increase the number and range of insect species present, and extend the period in which flowers are available to them.



Friday, 25 May 2018

The case for broader buffering benefits

Grass margins around fields are readily adopted by farmers within agri-environment schemes but are sometimes criticised for failing to deliver on the environmental objectives for which they are intended.  But such criticism often arises because too narrow a focus is taken on the benefits.  These include the ability to cut hedges later in the winter, after berries have been eaten by birds, and the provision of a habitat for pollinating insects and invertebrate crop pest predators. 

Our research into both field margins and the productive area can guide the development of integrated land management
The greatest potential is where grass margins are placed against watercourses, including ditches and small streams, as well as rivers.  Used in this way, their capacity to reduce movement of soil to adjacent watercourses is well established.  We have found that earthworm numbers are more than twice as high in grass margins as in the adjacent field, helping to improve infiltration and reduce surface runoff to water and acting as a refuge for recolonisation of cultivated land, as well as providing a food source for wildlife.

What plant species establish as a result of sowing or natural regeneration also influences the benefits realised by grass margins, as does their subsequent management.  We are exploring the traits and associated benefits arising from a range of perennial herbaceous plant species, with the aim of delivering multiple benefits.  The establishment and management of riparian woodland, where appropriate, is an extension of that process.

Buffer strips can be further enhanced by creating buffer pools within them to capture runoff, as we have been doing at Loddington since the 1990s, although the efficacy of these is limited on clay soils where very fine material is held in suspension.  Additional barriers within field boundary ditches serve a similar role. We have shown that, although eutrophic, pools fed by runoff can have additional biodiversity benefits for birds, amphibians and insects.  Where more permeable dams are installed in field boundary ditches or small streams, these have the potential to buffer downstream areas from flood peaks and we are currently evaluating these in our Water Friendly Farming project. Stacking multiple buffering measures requires additional knowledge, investment and management but increases the value of public benefits delivered from the same area of land.

But we know that each of these measures in non-productive areas has only a limited role in reducing the movement of sediment and nutrients to watercourses and additional measures need to be adopted within fields to improve soil function, reduce soil erosion, and deliver other benefits such as enhanced terrestrial biodiversity.  Research at Loddington has identified the potential of tramline management and reduced tillage intensity for example, and as reported in my March post, we have also explored the potential role of cover crops, and are currently investigating grass leys. An integrated approach to land management needs to be taken to meet environmental objectives, incorporating targeted evidence-based management of both productive and non-productive areas.

How effective these measures are varies considerably from time to time and place to place, a subject I will return to in a future post, but each of them has a place for their cumulative impact.  With new funding mechanisms for agri-environment schemes currently under consideration in the lead up to Brexit, there is considerable potential for a number of options to enhance the standard grass margins that are now widely adopted across the country.  One solution might be a modular approach to buffer strips with bolt-on options, but crucially, each adopted according to site specific, local circumstances.

It is vital to recognise that we can’t rely on buffers outside the cropped area alone, however elaborate they might become in some situations.  Soil management within the field, reducing erosion in the first place, is fundamental to catchment management and to meeting other environmental objectives, with a range of options for differing soil types.  But these require attention to detail, timely operation, capital investment, technical advice and support, and in some circumstances reduce crop yields.

There are still unknowns and a need for continuing research, and we continue to play a major role in that at Loddington, but we know enough about a range of field margin and in-field measures to adopt a package for improved land management that delivers food production alongside other public benefits.

Friday, 13 April 2018

Getting together around soil

If we felt we had got to know our local farming community fairly well over the past 25 years of the Allerton Project's existence, that process has stepped up a gear in the last couple of years through our shared interest in soil.  Today, a dozen farmers met at Loddington as part of our Soil Biology and Soil Health project with AHDB, led by Elizabeth Stockdale at NIAB.  'Health' assumes life, and this project explores the relationship between life in soils and farm production.  Several other farmers expressed regret at being unable to attend because cold, waterlogged, lifelss soils associated with the recent rains had delayed many arable operations and added considerably to the current workload for both arable and livestock farmers.
Our research brings together local farmers through EU, Defra and AHDB funded soil research projects at Loddington
As part of the Soil Biology and Soil Health project, we are investigating the impact of ploughing experimental plots through a long-term no-till field at Loddington and documenting the changes in crop performance and soil properties (of which more another time).  We also want local farmers to take soil samples on their own farms to contribute to our collective understanding of the relationship between soil management practices and agricultural activities and production, through their influence on the biological activity of soil.

More to come in due course - the soilquality.org.uk home page
A related initiative provides an opportunity for local farmers to collect soil samples for analysis and compare their results with those from other local farms, similar soil types, or comparable farming systems locally, or elsewhere in the country.  This project is at an early stage, with the first soil samples only just being taken, but results will be uploaded in due course to the interactive website at www.soilquality.org.uk where participating farmers will be able to compare their soil properties with those on other farms and consider the implications for their businesses.

In our EU funded project, SoilCare, local farmers have played a key role, through a carefully structured process, prioritising what research we should carry out.  As a result, we are now comparing a range of modern deep-rooting agricultural ley grasses, gathering data on forage yield and quality, and on changes in soil properties, including infiltration rates.  We are also experimenting with different ways of alleviating soil compaction and gathering data on crop performance and soil biology, as well as on changes to the physical properties of the soil itself.  Those farmers who were able to get to Loddington today were able to view these experimental plots and discuss the visible differences in crop performance.  Our research on cover crops as part of Defra's Sustainable Intensification research Platform (SIP), also provided an opportunity for local farmers to view and discuss experimental plots at Loddington (see last month's blog post).

While there is considerable interest from the farming community from the perspective of agricultural production and profitability (in an economic climate which makes this objective increasingly challenging), each of these research projects also has considerable relevance to catchment management. Foremost in many of our minds during the recent period of prolonged heavy rain is the potential for reducing flood risk.

Saturday, 17 March 2018

Cover crops research

The potential of cover crops to reduce impacts on water are fairly well understood, but the agricultural benefits are less clear, especially on the clay soils that are found across much of Lowland England.  Over the past two years this issue has been investigated by our Soil Scientist, Dr Felicity Crotty as part of our contribution to Defra's SIP (see my December blog post).




Sprayed off cover crops at Loddington, March 2018

In 2015/16, we tested three different cover crop mixtures against a control (no cover crop present), replicated across three fields.  In 2016/17, we tested the individual component species in those mixtures, with three replicates in the same field.  The first experiment adopted various mixtures of cereal, phacelia, radish and legumes, while the second experiment tested oats, phacelia, vetch, buckwheat and radish individually.  In each case, we monitored a range of soil chemical, physical and biological properties, as well as cover crop and weed cover, and the yield and weed cover in the following spring-sown oats crop.

Cover crop mixtures containing radish generally supported 4 times higher numbers of surface dwelling (epigeic) earthworms. Control plots had up to twenty-three times as much weed cover as cover crop plots.  In the following spring-sown oats, the yield, although low, was 60% higher in plots which had contained these cover crop mixtures, and the amount of black-grass and other weeds was up to six times higher in the control plots than the plots which had contained cover crops.

In the single species cover crop experiment, by February, epigeic earthworm biomass was 3.5 times higher in the radish plots than in the control.  Weed cover was over 5 times higher in the bare stubble control plots than in oats and radish plots which had good cover of the planted cover crops.  This provides a clear indication of the ability of some cover crops to supress weeds.  The yield of spring oats was 20% higher in plots which had previously contained radish compared to the bare stubble control plots, but overall yields were again low and the difference was not statistically significant.

The low weed burden in the spring-sown oats is likely to be due to improved rooting conditions for the cash crop and associated crop vigour and competitive advantage, rather than to supression of weeds in the cover crop. In fact, while a sparse, open-structured crop may have lower benefits to the soil in terms of organic matter contribution for example, higher germination of weeds in the cover crop provides more opportunity for weed control when the cover crop is sprayed off in late winter.  Such are the trade-offs associated with cover crops.

On clay soils in the Midlands, establishment of cover crops occurs later than on lighter soils and more southern locations, resulting in a less dense crop than can be achieved in more favourable conditions.  Cover crops also do not reach the stage of maturity that occurs elsewhere with the result that physical means of cover crop destruction such as crimping are not feasible and a glyphosate application is necessary, even if the cover crops are previously grazed by sheep.

While the costs of cover crops remain constant from year to year, the benefits are likely to vary with weather, harvest and soil conditions.  While weed control and water protection benefits are realised in the first year, cover crops that improve soil properties may have longer lasting implications for crop performance and water quality.  These are issues which are of considerable relevance to the economics of adopting cover crops and their role in environmental improvement.  New research being carried out at Loddington over the next few years will contribute further to this debate.