1. AGROFORESTRY:A REVIEW OF CURRENT KNOWLEDGE
Wakelyns Agroforestry, Suffolk
Bruce Pearce, Senior Programme Manager
The Organic Research Centre

2. Agroforestry: a multifunctional land-use system
“Land-use systems in which woody perennials (trees, shrubs etc.) are grown in association with herbaceous plants (crops, pastures) or livestock; there are usually both ecological and economic interactions between the trees and the other components of the system” Lundgren, 1982
This represents a concept of integrated land use that combines elements of agriculture and forestry in a sustainable production system. The emphasis here is on managing rather than reducing complexity. Agroforestry uses the natural woodland ecosystem as a model to create a dynamic, ecologically-based, natural resources management system which balances the production of multiple outputs balanced with protection of the resource base.

3. Agroforestry – a new name for an old practice?
Agroforestry systems have traditionally been important elements of temperate regions around the world, evolving from systems of shifting cultivation towards more settled systems involving agriculture, woodland grazing and silvopasture, with fertility transfer from woodlands to cultivated land via manure. Trees of high value, such as fruit trees, oaks and beech for acorns and beech mast, and ash trees for fodder, were retained during forest clearance and formed the basis of early agroforestry systems.

4. Separation of agriculture, forestry and nature
Increasing mechanisation leading to the removal of scattered trees to facilitate cultivations.
Increased productivity through monocultures.
A reduction in the agricultural work force.
A shift from small fragmented land holdings to larger single farms, with an increase in field sizes, the removal of boundary trees and landscape simplification.
Policy regimes that favoured single crop systems over crop associations.
The modern concept of agroforestry was first developed in the tropics in the late 1970’s, where rapid population growth in developing countries led to land shortages and a need for efficient production systems for both food and fuel. Results of research on temperate systems started to appear in the early 1990’s and there has been a recent resurgence in interest in agroforestry as a sustainable production system.

5. Silvoarable: trees and crops
Silvoarable systems combine trees and crops – most modern systems are laid out in alleys – the width of which are determined by the machinery in use. Popular timber trees in northern Europe include poplar, ash, walnut, sycamore, cherry.
Crops can benefit from presence of trees – shading reduces evapotranspiration; tree roots access nutrients below depth of crop roots and deposit on surface through leaf fall to increase soil organic matter.
Wind breaks – shelter crops up to 30 times the height of the windbreak.
Shelterbelts provide an important service by reducing wind speed in the protected area, reducing evaporative stress, and improving distribution and use of irrigation water, reducing evapotranspiration and improve crop water use efficiency. In Scotland, wind speeds under widely spaced Sitka spruce trees were less than half those in the open.
Fruit and vegetable crops are particularly sensitive to wind stress and suffer lower yields and poorer quality at lower wind speeds than agronomic crops. Horticultural crops grown in the shelter of a wind break benefit from moderation of temperature extremes, warmer soil and air temperatures, and improved soil water conditions, all of which contribute to increasing total marketable yields and individual fruit weight. Sheltered conditions increase flowering periods and bee activity, leading to increased fruit set and earlier maturity

6. Silvopastoral: trees and livestock
Trees are multifunctional in their provision of resources for animals; they provide shelter from rain and wind, shade from the sun, cover from predators, and a diversity of foraging resources, including fodder from the trees.
On wet days, the effects of wind reduction by tree shelter can increase the minimum temperature by 2 or 3°C
New Zealand silvopastoral system, Pinus radiata trees planted at 400 stems/ha-1 reduced wind run by 78% compared to open pasture, and densities of 100 and 200 stems/ha-1 reduced wind run by 44 and 45% respectively
Evaporative cooling is the primary mechanism by which cattle reduce their temperature, and this is affected by humidity, wind speed, and physiological factors such as respiration and sweat gland density. By providing shade, trees can reduce the energy needed for regulating body temperatures, and so result in higher feed conversion and weight gain.
Research in southern United States found that cattle that had been provided with shade reached their target weight 20 days before those with no shade (Mitlohner, Morrow et al. 2001). Higher respiration rates and lower activity rates of those cattle without shade were thought to reduce productivity.
During cooler months, windbreaks and shelterbelts provide valuable protection from the wind for livestock, particularly for new-born lambs and freshly shorn sheep. When livestock have been protected from winter storms by windbreaks, significant savings in feed costs, survival and milk production have been reported by producers in Dakota, US
Increases in percentage crude protein of silvopastoral pasture may be attributable to either a decrease in photosynthates (i.e. consequent rise in N concentration) or increased SOM mineralisation under trees providing more N for plant uptake
Feed value of willow is about 65-70% organic matter digestibility (Kemp, Barry et al. 2003), which is similar to lucerne hay. Crude protein levels vary throughout the season, with highest levels in the spring (17.0% and 19.6% for willow and poplar respectively)

7. Products Food Fuel Fodder and forage Timber Fibre Gums and resins
Thatching and hedging
Gardening materials
Medicinal products
Craft products
Recreation
Product diversification should increase the potential for economic profits, by providing annual and periodic revenues from multiple outputs throughout the rotation and reducing the risks associated with farming single commodities

8. Productivity
Land Equivalent Ratio (LER) the ratio of the area needed under sole cropping to the area of intercropping at the same management level to obtain a particular yield
Modelled relative tree and crop yields for 42 tree-crop combinations
research/projects/safe.jsp
A central hypothesis in agroforestry is that productivity is higher in agroforestry systems compared to monocropping systems due to complementarity in resource-capture i.e. trees acquire resources that the crops alone would not.
The Land Equivalent Ratio is used to compare productivity of agroforestry systems with that from monocropped systems.
Agroforestry systems LER’s:
Annual LER 1.6 in early stages to 1.0 in later stages
Over rotation LER 1.2 i.e. 4ha of AF = 5 ha of sole crops

9. Productivity: design and management
Species selection:
canopy
root system
allelopathy
N fixers
Spatial and temporal arrangement
Management:
Thinning and pruning
Weed control in early years
Protection from animals in early years
Agroforestry systems should be designed and managed to optimise resource capture by maximising positive interactions and minimising negative ones
Species selection – trees, crops and livestock
Hybrids. Rooting characteristics. Canopy characteristics. Deciduous vs conif. C3 vs C4 crops. Grass species, legumes for forage. Market forces. Growth speed.
Species choice – crown density, period in leaf, plasticity of tree root system
Significant transfer of fixed nitrogen to crops has been observed in a study by Seiter et al (1995, in (Jose, Gillespie et al. 2004)) which showed that 32 to 58% of the total nitrogen in alley-cropped maize came from nitrogen fixed by the adjacent Alnus rubra

10. Environmental Benefits
Air
wind speed
GHG
Odour
Water
‘safety-net’ hypothesis
flood control
Soil
Erosion
Structure
Fertility
Wind speed reductions can extend to 30 times the height of the windbreak on the leeward side, and 2-5 H (H= shelterbelt height) on the windward side
Potential capture or dispersion of ammonia theoretically was up to 15% for sites downwind of a tree belt.
Buffer strips can significantly decrease pollution run-off, with reductions of 70-90% reported for suspended solids, 60-98% for phosphorus and 70-95% for nitrogen.

11. Climate regulation – Global Climate
Mitigation: C sequestration, GHG abatement
Adaptation: extreme events, renewable energy
The potential for agroforestry systems to sequester carbon depends on a number of factors including system design, species composition and age, environmental factors such as climate, management and the end product.
calculation of 1.9 Peta grams of carbon over 50 years, based on a worldwide estimate of 1023 million ha of agroforestry.
Converting unproductive croplands and grasslands to agroforestry, an estimated 630 million ha, could potentially sequester 391,000 Mg C yr-1 by 2010 and 586,000 Mg C yr-1 by 2040.
Estimated 63 Mg C ha-1 in temperate agroforestry systems
Schoeneberger, 2009

12. Biodiversity Benefits
Pest & disease regulation
Pollination
Increased connectivity between habitat remnants
Reduced rates of conversion of natural habitat and resource use pressure

13. Agroforestry in UK policy
Eligibility for SFP
Agri-environment schemes
Recommendations for changes:
Valid land use for SPS - Definition of agroforestry
Adoption of Article 44
AES options
Other options – community supported agriculture, carbon credits, payments for ecosystem services?
The eligibility of agroforestry systems for SPS within the UK depends to a great extent on the nature of the woody component in the system. If the trees are managed for timber or wood fuel and tree densities are above 50/ha, this area of land is ineligible for payments unless the area can be grazed or agricultural activities can carry on in the same way as if trees weren’t present.
Agroforestry systems that include permanent crops such as top fruit, hardy perennial soft fruits such as blackberries and raspberries, nuts and vines are eligible for payments, as are short rotation coppice systems. In these cases, the field area containing the trees and crops would be split and areas allocated to each component. While nut trees in widely spaced rows of agroforestry systems can be supported under the SPS, they would not be eligible for additional funding under the Area Payments for Nuts scheme. Boundary hedges are included in the area eligible for aid, unless they exceed a certain width.
The primary focus of agri-environment schemes within the UK is to protect the environment. Most options aim to enhance the environmental, biodiversity or cultural value of farmland through careful management of existing features such as hedgerows or the introduction of semi-natural habitats including grass buffers. As such, productivity is of secondary importance. While agroforestry systems provide a means of improving ecosystem service delivery on farmland, the management needed to maintain productivity often conflicts with management requirements specified by the schemes. The biodiversity and cultural value of permanent woody features such as hedgerows and in-field trees are targeted under all AES’s, promoting the use of native species and carefully controlling the cutting regime to create a valuable habitat. Traditional agroforestry methods such as parklands, wood pastures and traditional orchards are also valued particularly for their cultural heritage, and several options support the restoration and maintenance of these systems. In both cases, management is targeted at improving the biodiversity and/or cultural value of these features, and their value as multifunctional systems that balance productivity with environmental protection is not considered.
Two schemes that can provide support for agroforestry in England, although not implicit in their design, are the Energy Crops Scheme and Conversion Aid payments for top fruit orchards. The Energy Crops Scheme states a minimum block size of 0.5 ha, which potentially could fit within an agroforestry design, while the conversion aid payment for organic top fruit orchards has no minimum block size but requires certain planting densities.
Farm woodland schemes are available across the UK to provide compensation for the loss of agricultural income following conversion of agricultural land to forest, as well as contributions towards the costs of planting and looking after the trees. Within most of these schemes, tree densities are above those that would be found in an agroforestry system, the exception being in Northern Ireland. Here, they have adopted Article 44 which supports the first establishment of agroforestry, and payments are made on a pro rata basis depending on tree density.
“Agroforestry systems refer to agricultural land use systems in which high-stemmed trees are grown in combination with agricultural production on the same parcel. The tree component of agroforestry can be isolated trees, tree-hedges or regularly spaced low density tree stands. An agroforestry parcel is defined by two characteristics: at least 50% of the plot is in crop or pasture production; and tree density less than 200/ha (of stems greater than 15cm diameter at 1.3m height), including boundary trees.”

14. Eco-Agroforestry Network aims
Collate, manage and, through research, provide evidence on the benefits of eco-agroforestry to balance production with delivery of ecosystem services.
Identify and promote clear market and policy reasons for adopting an eco-agroforestry approach.
Support knowledge transfer to land managers and farmers, policy makers, conservation organisations and researchers.
Improve conditions for establishing agroforestry in the UK and Europe.

15. Information on Agroforestry
Books
Agroforestry in the UK (2000). Eds. Hislop, M. and Claridge, J. Forestry Commission Bulletin 122
Temperate Agroforestry Systems (1997). Eds. Gordon, A.M. and Newman, S.M. CAB International, Wallingford
Journals
Agroforestry Systems
Websites
Farm Woodland Forum
Agroforestry Trust
Silvoarable Agroforestry For Europe www1.montpellier.inra.fr/safe/
FarmSAFE and PlotSAFE: spreadsheet models for comparing the growth and profitability of arable, forestry and agroforestry systems
myForest – linking the woodchain:
DVD: Agroforesterie Produire Autrement (Agroforestry - Alternative Production) by Fabian Liagre & Nicolas Girardin
PlotSAFE – predict the per hectare growth and profitability of crops and trees in arable, forestry, and agroforestry systems
FarmSAFE - comparing the profitability of arable, forestry and agroforestry systems at a one-hectare and a farm-scale

16. Interested in getting involved?
Web-site:
Agroforestry: Reconciling Production with Protection of the Environment. A Synopsis of Research Literature
Contact Jo Smith, Agroecology Researcher, Organic Research Centre