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The promise of agroforestry

Date Published: 11/10/2012

When it comes to the most effective methods of producing food, we don’t know it all. We certainly, as the human race as a whole, are not embracing some of the more diverse and potentially efficient and sustainable ways of producing our food for the future. Agroforestry is one area with a lot to teach us and tremendous potential which is perhaps not yet anywhere near as widely recognised as it could be.

OF&Gs’ Research and Development Officer, Steven Jacobs, recently spent a day finding out more about agroforestry, including where knowledge of the topic currently stands and where it appears to be going. Here he shares, in-depth, what he learned on the day – and it makes for a fascinating read.

Agro-Forestry Workshop

Peterborough, Cambridgeshire, Thursday 20 September 2012

Silviculture is the care and cultivation of forest trees, more widely known as forestry. Agriculture can be defined as the cultivation of land to produce crops and/or raise livestock, otherwise known as farming.

Agroforestry in action, just outside Peterborough
And this is how it’s done. The fruit trees are on dwarf root stock, partly to avoid them growing too tall and overly shading the crop, plus to make them easier to pick, and other benefits.

Forestry farming is known as ‘agroforestry’ (with or without a hyphen) and is where silvo- and agri- culture meet. The aim is to produce crops from the trees, such as fruit, nuts and timber, and from the land the trees are on, such as cereals (silvoarable) or with livestock, which is (silvopastural) agroforestry.

“Forests and other wooded land cover more than 40% of the European Union’s (EU) land area, and the EU is set apart from many other global regions insofar as it is one of the few regions of the world where forest area is currently expanding.” So states a report on the website of Eurostat – the statistical office of the European Union.

This was one of the headline facts I came away with after attending an excellent IOTA Agro-Forestry workshop held recently just outside of Peterborough.

Typical of such practical educational meetings it was held mainly in the back room of a local pub. Un-typically, though, the pub is but a few minutes walk from a 100-plus acre agroforestry system on an organic farm – Whitehall Farm. The farmer is Nuffield Scholar, Stephen Briggs.

The workshop heard contributions from experienced organic advisor Mark Measures of IOTA (http://www.organicadvice.org.uk/), from Mr Briggs himself and from Dr. Jo Smith, senior agroecology researcher at the Organic Research Centre (http://www.organicresearchcentre.com/) and from the two-dozen attendees who came to Peterborough mainly from across the UK, one person attending from Libya, and a variety of backgrounds from dairy farmers and small holders to advisors from Natural England and The Woodland Trust.

Why Agro-forestry and the role of advisers – Mark Measures

Mark Measures of The Institute of Organic Training and Advice (IOTA) introduced the workshop and led the initial discussion on agroforestry (AF) pros and cons. Between us we could think of three times as many pros ranging from soil erosion control and carbon sequestration to long-term investment (although the latter was also in the cons list).

Agro-forestry Nuffield Scholarship – an international study tour – Stephen Briggs

In his Nuffield Farming Scholarship report organic farmer and advisor Stephen Briggs focussed on the adoption of commercial agroforestry in this country. But to gain insight Stephen travelled around the world visiting important sites in Europe, New Zealand, Canada, North America and China in his search for practical examples of AF at work.

An example of the excellent soil at Whitehall Farm.
An example of the excellent soil at Whitehall Farm.

His finished report is available to download and at over 52,000 words it is, to say the least, rather comprehensive.

Stephen defines AF as ‘.. an integrated land use system that combines elements of agriculture (agro) and trees (forestry) in a sustainable production system.’

Some key facts from Stephen’s report:

‘The UK has about three million hectares (Ha) of forest and woodland, or 11% of the land area (66% is agricultural area). International comparisons include Europe (excluding Russia) 37%; North and Central America 33% and Finland 74%. (Forestry Commission 2009).’

Stephen Briggs explained to us that research indicates that although cereal plants will root quite deeply, which is not something everyone in farming is aware of, typically tree roots can grow much deeper than cereal plants.

Where the cereal crop gets going first each spring trees want their nutrients and water later and they will carry on growing later. As the tree roots go deeper different elements become available which is known as resource partitioning. The tree’s roots are then mining nutrients from deeper underground with their resulting leaf litter spreading those nutrients on the ground above making accessible a great resource otherwise hidden from the crops.

With our knowledge of agroforestry (AF) theory in much better shape Stephen moved on to show us some wonderful international examples of AF at work.

Here are just a few:

The Spanish Dehesa, where 3.5 million Ha (nearly 3% of the area) is under agroforestry, enabling a sustainable life for the local inhabitants and for a diverse population of wildlife with good, sustainable soil maintenance.

An AF system in South Eastern France where the existing trees are being used to support irrigation for vegetable alley crops underneath. Infrastructure can count for as much as 30% of the cost of installing irrigation and not only was money saved, in this instance, but raising the pipes provided easy access beneath reducing the need for more specialised machinery to attend to the crops.

The Missouri organic pecan farm with grass between that is mown for forage or grazed. The grass is managed carefully as the nuts will be harvested off the floor once the trees are ready and those pecans are a very valuable crop. The farmer reports higher grass yields than his monocultural neighbours. He attributes this directly to the effects of leaf litter.

At the University of Missouri there are a number of research programmes. One looks at riparian (of or relating to wetlands adjacent to rivers and streams) buffers to ‘seize’ nutrients and in so doing also ‘filters’ away from the nearby watercourse a host of pollutants including veterinary antibiotics and even hormones from the human contraceptive pill going into the water course. Apparently ‘the pill’ is heavily used in the caravan park up-stream. It’s contamination of the water had resulted in infertility in the local cattle.

The Centre d’Ecodéveloppement de Villarceaux has a 42Ha agroforestry site producing walnut, cherry, oak and almonds on trees “using both 28m and 52m spacing between tree rows, with 2m left as a clover strip either side of the trees resulting in a 24m or 48m working area for each alley.” Saler cattle graze beneath the trees with wheat included in the rotation. One of the big issues, apparently, is protecting the trees from cow damage. They like to rub up against the tree trunks.

The French National Institute for Agricultural Research (INRA) has fascinating data on the impact of light shade tolerance in crops. Using trees with smaller leaves, paulownia and poplar in this case, allows more light to reach the crops. And using different pruning regimes can have a dramatic effect. At 10m (height) pruning allowed 50% light availability. Whereas at 7 m pruning east-west oriented trees resulted in just 30% light availability as opposed to 42% for north-south oriented trees.

In China Stephen learned that 80% of the population is farming. 3.5million Ha has been planted with agroforestry in just 30 years. The result has turned huge flooded areas into highly productive farmland.

The UK has, by proportion, some of the lowest tree coverage and highest amount of agricultural land in Europe. Which neatly brings us on to the visit to Stephen’s own version of agroforestry here in this country.

Visit to Whitehall Farm agro-forestry – commercial experience of apple/cereal system

Taking a tour of the agroforestry work at Stephen Briggs' farm.
Taking a tour of the agroforestry work at Stephen Briggs’ farm.

Stephen and his wife, Lynn, established 125 acres of agroforestry at Whitehall Farm in 2009. They have planted 4,500 apple trees with combinable and vegetable crops. This is currently the largest agroforestry system in the UK.

The aim is to be profitable whilst also providing improved levels of biodiversity and soil protection.

They’ve used apple trees for the initial phase of the project. Stephen says that if he can secure a longer term tenancy then nut and timber trees, which have the potential for greater financial return, would also be considered.

The soil at Whitehall Farm is tremendous. It is organic sandy clay loam with the following indexes: pH 7.2, P index 4, K index 3 Organic matter 23.8 % (very high). It is rich, dark and wonderfully crumbly.

The trees are planted in 3m wide rows orientated north east/south west. The alleys are 24m wide and are sown in rotation with cereals and green manures. A variety of green manures are in evidence including birdsfoot trefoil and several types of clover. The tree density much higher than in conventional orchards in the rows but less when looked at across the fields.

One of the drawbacks to planting trees in fields, Stephen explained, is that it does provide roosting for larger birds (pigeons particularly). The young trees branches are easily damaged when the birds land on them. The solution has been to put in very tall wooden stakes for the birds to perch on so they don’t land on the trees at all. Another issue has been that new trees have drawn the attention of the local rabbit population who seem extraordinarily tall and so Stephen has doubled up the metal tree guards.

One of the bonuses is increased numbers of wildlife. Mice and voles inhabit the green manures in the field and owls are frequent visitors and now live at the site in special owl nest boxes Stephen and Lynn have put up on farm buildings very close to the trees.

UK Agro-forestry research and development and networks – Jo Smith

Dr. Jo Smith gave the last presentations of the day and she began by carefully explaining that one of the keys to understanding agroforestry systems is to look closely at the complex interactions occurring not only between the trees but also in their relationship with the soil and any crop, including livestock.

Jo gave us a brief tour of UK Agroforestry Research. A number of interesting results from both Silvopastoral and Silvoarable sytems:

– Slightly decreasing crop yields (10% in years 4 and 6) in silvoarable systems over time;
– In silvopastural systems one drawback is compaction around the trees from the livestock as they do tend to shelter under the trees;
– In both there is a marked increase in biodiversity and where nitrogen fixing species are used, such as red alder, there is an increase in productivity in line with pasture control plots with 160 kg N ha-1 yr-1 applied.

We looked at the ORC research station at Wakelyns in Suffolk. It is a 22.5 Ha site with willow and hazel coppice, mixed hardwood and fruit trees with an organic arable rotation. I’ve visited the site before and can testify that it is a hugely fascinating project. They have a wonderful woodchip boiler fed by the willow coppice grown at the site. It’s a very efficient and well-constructed system and a well-designed site with everything weighed, measured and discussed in great detail.

The CO-FREE project (http://www.co-free.eu/index.html) is a pan European research project running from January 2012. The Organic Research Centre (ORC) is a project partner with the role of the evaluating ‘the potential and the limits of agro-forestry based apple production systems as a sustainable strategy for replacing copper inputs in organic and low-input systems using Wakelyns and Whitehall Farm as case studies’.

The report on ‘evaluation of novel agroforestry-based apple production systems’ is scheduled to be released towards the end of 2015.

Dr Smith then discussed land equivalent ratios (LER). Though difficulties do arise in agroforestry systems in measuring all of the inputs and outputs the LER can determine the impact and productivity of multi-cropping systems such as agroforestry.

Where the LER is greater than 1 the combined yield is greater than that of a monoculture system by comparison.

At Wakelyns they have been able to demonstrate the LER of in excess of 1.30 This means that at least 30% more land would be needed in a monoculture system to produce similar yields when taking agroforestry (AF) combined yields into account. A cereal crop yield alone may be lower in an AF system than in monoculture but the overall or combined yield, when including that of the forestry, can be much higher.

A lot more research is needed in agroforestry and its potential benefits. Dr Smith cited the European Commission’s Seventh framework programme with a budget of €8.1 billion that will include aspects of organic farming and agroforestry.

More in terms of support not least in governments and public bodies having a greater understanding of the role of agroforestry in the commercial farming landscape. The European Agroforestry Federation (EURAF) has made proposals to the upcoming Common Agricultural Policy (CAP) reform. These include making agroforestry land use classified as eligible land use in basic farm payment systems including in-conversion as well as first establishment on both agricultural and forest land. Also to increase maintenance support to 10 years as a minimum and to widen the scope to include silvopastoral as well as silvoarable systems.

Conclusions 

Stephen Briggs sharing his extensive knowledge of agroforestry with his visitors.
Stephen Briggs sharing his extensive knowledge of agroforestry with his visitors.

After seeing and discussing a wealth of data we can safely conclude that agroforestry systems have positive measurable outcomes. Increases in biodiversity, including ground species and birdlife, soil condition including nitrogen, and in productivity when combining yields. AF systems can also increase community activity when looking at the greater variety of livelihoods that can be sustained where systems include nut/orchard produce with livestock/cereal production, which for me is one of the most overlooked and yet most important aspects when looking at the future of farming.

In Stephen Briggs’ own words: “Agroforestry is ‘climate smart’ agriculture and provides one of the very few options that has the potential to help reduce greenhouse gas emissions and help protect natural resources whilst, at the same time, producing more food and biomass.”

More trees in more carefully thought-out plantations (agroforestry) will be far more beneficial than is the current commercial thinking. This is what we see around the world. Some of us would like to see this develop more strongly here in the UK.

Places to go for more information and where to look for tree stock include the following: