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17.03.2015 The Shropshire Agroforestry Project

Getting in to Agroforestry

by Peter Aspin, Shropshire Agroforestry Project

My personal interest in silvopastoral agriculture (i.e. the integration of trees into permanent pasture) developed from two angles. Firstly, the observations over several decades of the interaction of cattle with trees in terms of using them for browsing - cattle are most definitely not simply grazing animals, and shelter, be it sun, rain, wind or cold. Secondly, becoming fascinated by the concept of forest gardening, the main practitioner of which in Western Europe was a man from the south of this county, Robert Hart.

As I developed a small forest garden, I became more fascinated by the concept of agroforestry throughout the world and began to develop a system here almost fifteen years ago, initially simply using ash and walnut trees but as my interest and knowledge and curiosity developed, planting many other species which I felt had a relevance and requirement of further research.

The integration of tree crops into pasture or arable crops goes back hundreds, if not thousands of years. Most people know of the age-old practice of growing cork oaks in pasture in the Iberian peninsula, known as “dehesa” in Spain and “montado” in Portugal. In the seventeenth century, the diarist and arboreal advisor to Charles II, John Evelyn, commented on the management of walnut trees in wheat fields in northern France and how little they affected the yield of corn.

Agroforestry systems are well-developed in much of Asia, especially China, but these are largely silvoarable in nature. The Holy Grail in agriculture has for many years, and continues to be, perennial corn and I often wonder why no independent farmers in the UK are prepared to research the likely candidates. But the ultimate perennial crop is the tree, with so many myriad uses of all its component parts.

How it started here

Climate was the spur to the research here. I sold the dairy herd here in 1996 and since then reared beef cattle bought in as calves. About half were black, either Limousin or Angus crosses. On hot summer days they were very uncomfortable in open fields and many spent large parts of the day in the buildings, which is obviously not good for liveweight gain.

We’ve probably all observed cattle in the shade of trees or hedges. The hot summer of 2013 was a perfect example of how not to keep cattle in large open fields without shade, resulting in many losses and production problems. We are told that the average temperature will increase by 2-3 degrees centigrade by the end of the century. But the mean figure inevitably hides the extremes.

Much work has been done in both the UK and the USA about the use of trees to moderate urban temperatures, none as far as I am aware in terms of crops or livestock, and this continues to be part of the research here. As well as providing actual shade, agroforestry also produces convection currents as the warmer air away from the trees rises, drawing in the cooler air from beneath the canopy. And trees in leaf produce copious amounts of oxygen as they separate the components of carbon dioxide.

How it works on my farm

Planting here is in rows aligned north-south at five metre intervals between individual trees, with slightly larger distances to the headlands for machinery operation. There is a single permanent electric fence either side of the row to prevent damage by livestock. Spacing between rows is twenty metres, which I felt was the absolute minimum where cattle are grazing, without resulting in a “corridor” effect where the cattle spend too much time and effort going up and down the alley, and not enough foraging. Therefore on this farm the cattle are allocated a length of, say, 100 metres or 150 metres, depending on forage growth, multiplied by the width of the alley, 20 metres.

The most efficient shape to graze is the square, maximum area, minimum length of boundary. If this had been a larger farm, then inter-row spacing would have been 30 to 50 metres, but as I needed to get as many trees as possible (500 plus) into the area (20 acres), options were limited.

Browsing animals

As mentioned earlier, bovines are to a considerable degree browsing animals. The main browsing tree in the past has been the English Elm, but since its demise its place has been taken by the ash. However, virtually any deciduous tree or hedging plant (especially at leaf emergence) will be readily consumed. A recently retired veterinarian I know jokes that he has the healthiest and quietest flock of sheep because of the salicilin (aspirin) they intake from the abundant willow in the hedgerows.

Indeed, livestock often prefer tree foliage to ground forage. And so many species of trees are grown here to provide forage for the cattle, and though the medicinal effects are vague and unproven, the very fact that there is developing such a varied diet as the trees grow, will manifest itself in healthier animals. The diet of so many farmed animals today is so frighteningly narrow.

We have all been made aware recently of the degradation of our soils, fertility and structure, that has taken since the last ice age to build up, being lost at an alarming rate. Virtually every time I am in the countryside, I see appalling land management which takes no account whatsoever of the long term damage to the land.

The finest soil conditioner of all is leaf litter and there are two methods of leaf fall in autumn. Wind induced defoliation disperses the leaves over a wide area. Frost induced defoliation concentrates the leaves below the tree, which can result in damage to and destruction of perennial crops. Some years in early winter harrowing is essential beneath mature oak, and especially sycamore, trees along the farm boundaries to prevent this. On the whole, the small leaves or leaflets of trees such as elm, robinias (black locust) or gleditsias (honey locust) are quickly absorbed . The larger leaves of trees such as walnut, sweet chestnut or sycamore take much longer to degrade or be taken below the surface by invertebrates. But generalisations are not possible.

The all-important tree of Chinese agroforestry, the foxglove tree (Paulownia spp.) has very large leaves but these degrade rapidly and are not problematic. The high calcium content of deciduous leaf-litter also tends to neutralise the soil (increase the pH), whilst, conversely, the leaf-litter of coniferous trees acidifies the soil over time.

Trees grown at Shropshire Agroforestry Project include:

Ash

Walnut

Sweet chestnut

Hazel

Almond

Hickories

Gingko

Monkey puzzle

Hackberry (Celtis),

Black and Honey Locust

Pasture management

As far as I am concerned, the plough is an instrument of last resort, a means to repair the result of poor management. Three alleys (6 acres) where the grass/clover components had become unproductive, owing to such poor management and excessive leaf fall damage, were reseeded in the autumn of 2014. It is ten years since any of the land was last ploughed and I foresee no need for it in the future. If any sward becomes short of an ingredient, perhaps clover, then I broadcast that just before grazing so that the cattle tread the seed in, so long as the ground is not too dry. This alley is then taken out of the grazing rotation and cut for silage seven to eight weeks later to enable the new seedlings to emerge and consolidate. I also use the traditional method of reseeding hay meadows whereby the sward is allowed to go to seed before cutting. The resultant tedding of the drying grass distributes the seed-heads across the pasture which the machinery wheels then incorporate into the surface layer.

The effect of this system of farming on drainage is very interesting. A few years ago a water mains burst in the main road running alongside the farm exemplified this. The alleys which had just been grazed were flooded owing to the recent soil compaction, but the rows where the trees were planted absorbed the water very quickly and the flooding came to a very sudden end by the third row. This outcome has also been observed after heavy thunderstorms. In the dry summer of 2014, narrow fissures running several inches deep along the rows of trees were conspicuous. Conventional thinking concerning field drainage is probably not appropriate in agroforestry.

The forage is conventional long- term organic seed mixtures with a fairly high proportion of white clover. Some herbs have been included in the past but the only persistent one has been yarrow.

Tree pruning

In the first few years after establishment, tree pruning to shape is essential. The ideal is to have a clear stem of about two metres with branches radiating out from this height. Much below this figure and ground shading would become a major problem affecting yields of the crop beneath. The usually accepted critical figure is one third canopy cover, below this level crop production is barely impacted, but above it production loss begins to become significant.

For similar reasons late leafing trees are necessary in agroforestry systems. In Asia the aforesaid foxglove trees (very fast growing producing timber for construction) are often grown with wheat, which invariably reaches its full height before the trees come into leaf, so all the corn then has to do is ripen as shading intensifies. Here, about forty varieties of walnut have been established, and some do not come into full leaf until the second half of June, so grass production is barely affected.

All crops grown under shade tend to become “leggy”, that is tall and thin. Here, this is especially apparent on the southern boundary where an existing mature row of trees shades the ground all year round. But this accidental shelter belt has benefited the rate of growth of trees planted within its influence. Conventional high-yielding ryegrasses prefer to grow in full sun whereas fescue grasses grow well in some shade. The reseeding last autumn included a percentage of Fest(ul)olium which is a ryegrass/ fescue hybrid in order to try to maintain high growth rates under conditions of some shade.

As well as walnuts, other nut trees established include sweet chestnuts, hazels, almonds, hickories, gingkoes and monkey puzzles (araucaria); browsing trees include a number of species of ash and elm, several varieties of hackberry (Celtis), black and honey locust trees (both also leguminous),timber trees include hornbeam and sweet gum (liquidambar) and Liriodendron (tulip trees) but there are also trees for rubber and cork production, even root beer. However, all trees by their very nature are multi-purpose: walnuts not only provide nuts and timber and edible sap but the smell of their foliage deters biting flies and when the cattle begin to browse the astringent leaves you know they are hungry and need moving on to the next rotation block.

Further developments

However, there is so much more research that needs to be done concerning the integration of trees and ground cover crops. I had hoped to establish a curvilinear system on another twenty acre field, to discover at what angle to due north yields were highest. Also which would depend on latitude, prevailing wind direction, strength of morning to afternoon sun etc., but that is for others now. On sloping land, contour and spiral contour strategies need to be assessed. If temperatures are to rise then wind velocities will become more problematic making shelter belts essential. And, of course, these landscapes/treescapes must be established decades before they are required. Finally, and in purely economic terms, it is usually accepted that production from an established agroforestry system has a fifty per cent higher total output than the same area of land devoted separately to conventional cropping and woodland.

Peter Askin

Shropshire Agroforestry Project

13.03.15 Planting trees on-farm: funding options

The Woodland Trust offers financial and practical assistance to help farmers benefit from trees, supporting business objectives and the environment.

Benefits from farm trees

Cost effective livestock shelter - extending the period animals can stay outside

Control stock movement - keep stock away from unsuitable areas

Shelter for crops - improve plant water efficiency by slowing wind speeds

Soil management - protect soils from wind and water erosion

Reduced flood risk - improve water infiltration by up to 60 times, helping water travel deep into the ground

Cleaner water - trapping agricultural pollutants

Reduce costs - by growing on-farm firewood supply or woodchip bedding

Boost pollinators - trees sustain pollinators when other food sources may be scarce

Sporting interest - provide valuable cover for game and other wildlife

Landscape value

Funding to plant farm trees

Through the PUR project farmers are able to access:

  • a whole farm tree assessment
  • thoughtfully designed planting schemes tailored to your farm business
  • advice on tree planting, maintenance and management
  • free trees and guards
The scheme is quite flexible and can be adapted to your needs - for example planting shelterbelts, riparian strips, pasture trees, woodland or developing agro-forestry systems
For more information please contact 01476 452356 or click here.

Watch the video of Stephen Briggs our great blogger from earlier this week.

Following on from the fab article that Stephen Briggs wrote earlier this week on implementing agro-forestry systems on his farm, here is a video produced by the Woodland Trust that shows him explaining his reasons behind the project and some great footage of the farm.

09.03.15 Climate smart cropping with new horizons

Stephen & Lynn Briggs rent a 105ha farm in Cambridgeshire, UK. Stephen is also a farm business consultant with ‘Abacus Agri’ where he specialises in organic arable production, and is the author of the book ‘Organic Cereal and Pulse Production’. Lynn is also an environmental consultant as well as helping run the farm.

The farm set up

Given their passion for organic farming and conservation, it is unsurprising that the farm was converted to organic as soon as they started renting the farm in 2007 on a 15 year agreement. Our overwhelming challenge is to develop an organic farming system with a balance of productivity and environmental management that is suited to high quality peat soils, which produces a good financial return and which is sustainable in the long term, on a farm where soil fertility is good but where the challenges for weed control are high. Another major concern is that the light peat soils on the farm have very high levels of organic matter (c.23%) and are subject to oxidation and wind erosion – and a loss of the farms most important resource. We wanted to do something that would protect the soil whist retaining productivity and enhancing biodiversity.

System design

With previous experience from time spent working in Africa and recognising the environmental and economic benefits of agroforestry, they were keen to develop a system at the farm to create a mixed tree & arable crop landscape on 52ha. With changes to the EU CAP Pillar 1 Scheme in 2009, apple trees were chosen as the tree species. We chose apple trees as we wanted to get a commercial return within the period of our farm rental of 15 years. If we had a longer rental period, nut, coppice or timber trees could be considered. Diversification into apples, along side or indeed, mixed in with arable crops creates a greater enterprise mix or perennial and annual crops, spreading cropping risk, whilst also capitalising on a resurgence in demand for English apples. After setting out the planting rows, MM106 semi-dwarf root stock were planted. Thirteen different varieties were planted for eating and juicing markets, with varieties selected for taste, good storage, pollination, disease resistance and late ripening. Late ripening was important so that apples can be picked after the cereal harvest in the autumn. After harvesting arable crops in the autumn, the farm will move straight from cereal to fruit harvesting, and the risk of a difficult harvest will be spread over a wider harvest window.

Compared to a normal orchard with over 1000 trees per ha, a planting density of 100 trees per ha allows normal farm equipment to be used, eliminating the need for specialist orchard machinery. This keeps fixed and operational costs down and means any equipment is multi purpose.

Between the rows of trees there is a 24m wide cultivated area for the cereal, root or vegetable crop. We held our breath when drilling the first cereal crop between the rows of trees, but the layout worked, the cereals performed well and there were no problems with harvest. But we did remind the combine driver to drive straight!

Unlike a new orchard where all the land is occupied by trees and narrow alleys, approximately eight percent of the land area is now occupied by trees. This means that we can continue to crop ninety two percent of the area whist we waited the five years for the apple trees to reach commercial productivity. This is a major plus point for the system with regard to cash flow. The arable crops provide short term income and the trees and fruit provide longer term income and a capital asset.

They have also introduced a wide range of conservation measures, including over winter cereal stubbles, green manures, feed plants for wild birds and Nectar flower mixtures, multi species legumes and wild flowers sown beneath the tree strips to attract insects and pollinators – important for fruit production and beneficial to surrounding crops.

On reflection Stephen and Lynn sum up “we think what we are doing at Whitehall Farm is creating a sustainable business integrating conservation and profitable farming using some very novel approaches, which we believe have a bright future and which create new horizons - literally !

A couple more pictures of Steve and Lynn's farm

 






















Some background on agroforestry

Agroforestry is a concept of integrated land use that combines elements of agriculture and forestry in a sustainable production system. Agroforestry systems are classified as silvoarable (trees & crops) or silvopastoral (trees & animals). With an emphasis on managing rather than reducing complexity it promotes a functional bio-diverse system that balances productivity with environmental protection. Systems can combine production of a wide range of products including food, fuel, fodder and forage, fiber, timber gums and resins, thatching and hedging materials, gardening materials, medicinal products, recreation and ecological services. Tree species can be timber, fruit, nut, coppice or a combination etc, and the rows in between trees can produce cereals, vegetables, fruit, forage etc. Careful selection of crop components is required in relation to market outlets, local climate, soil, alley spacing, tree height, planting and harvesting timing, tree leaf production and shading etc.

Agroforestry systems modify local microclimatic conditions (temperature, air water vapor content, evaporation and wind speed) and provide benefits to crops which are grown with the trees by reducing soil degradation and enhancing biodiversity, pest and disease control. Agroforestry also reduces nutrient loss by maximizing internal nutrient cycling through leaf litter return.

Cropping the extra dimension

Most crop production systems exist by exploiting sun, air, water and soil nutrients in a relatively thin layer above and below ground, typically no more than a meter or so. Combining trees in the system can make much better use of these resources in space and time. Tree roots access nutrients and water at greater soil depth than most farmed crops and branches make better use of sunlight above an understorey crop. Agroforestry systems use resources over a longer period of the year. The secret is to combine complementary components. For example, cereals require most resources from April – June, whereas a later leafing tree species may require most of its water, sunlight and nutrients later in the summer and autumn after the cereal has ripened. This allows the farm to better utilize natural resources and also crop an extra and widely underutilized dimension, upwards!.

There is a growing understanding that agroforestry can provide multi-functional land use and environmental benefits. These are not yet clearly acknowledged or understood by UK farmers or policy makers. By integrating trees into the agricultural landscape there is also a real potential to impact on the local economy by increasing economic stability, diversification of local products and economies, diversification of rural skills, improving food and fuel security, improving the cultural and natural environment and the landscape diversity. Combined with the positive impact of agroforestry on resource use, resource protection and climate change mitigation, the benefits of agro forestry are slowly becoming better understood and documented. However, the role of agroforestry in protecting the environment and providing a number of ecosystem services has not yet been fully appreciated in the UK.

Article written by Stephen Briggs, Whitehall Farm.

06.03.2015 Agroforestry Ammonia Abatement, practicalities, implications and policy

This work was done by the Centre for Ecology and Hydrology in Scotland, in collaboration with work in Spain and France. It looked at the potential for abating ammonia emissions from livestock production systems.  80% of the UK’s ammonia emissions come from animal manures, either from livestock housing, storage or spreading – a further 10% comes from inorganic fertiliser.

Planting tree shelterbelts upwind and downwind of livestock housing or slurry storage facilities will reduce ammonia emissions in two ways. Firstly the shelterbelt will result in a lower wind speed directly above and around the building or slurry store and thereby will increase the time taken for emitted ammonia to be transported away in the air. Secondly the trees will recapture a proportion of the emitted ammonia both directly through cuticular uptake and indirectly through increased deposition.

In addition to the recapture of this emitted ammonia, there are additional benefits of agroforestry systems including animal welfare, carbon sequestration, options for wood fuel and the protection of semi-natural areas. However in order to be able to quantify the effects and benefits of agroforestry systems, so that a national planting policy could be developed, there needs to be scientific research and modelling studies to provide the evidence and research into practical implantation (for example the choice of tree species, structure and planting area), for maximum ammonia recapture.

This research looked at quantifying the effectiveness of ammonia recapture and it’s knock on benefits using a range of modelling, lab and field experiments, as well as case studies, to look at what the potential is for UK wide agro-forestry ammonia abatement.

What did they find?

A wind tunnel experiment looking at ammonia recapture, found that a belt of small conifer trees were capable of recapturing up to 18% of ammonia emitted.

When this was scaled up (release under a forest canopy) the results were less clear.

Three case studies carried out for 6 months found woodland to be significantly abating ammonia levels at local level, both via dispersal and uptake.

Theoretical configurations using models were also tested. Results showed that leaf area index (LAI) and leaf area density (LAD) play an important role in recapture efficiencies.

Up to 20% recapture potential was modelled for a housing / lagoon with a 25m main canopy and 25m backstop stand of trees down wind and a 45% recapture for understorey livestock with 100m main canopy and 25m backstop.

Tree belts can be seen to significantly increase carbon stocks

Timber production from tree belts are not financially feasible because of small scale and high arable opportunity cost.

Applying a UK model shows that silvopastoral practice has the potential to reduce national scale emissions of ammonia by up to 2.9% resulting in a 2.2% reduction in deposition.

What does this mean?

Agroforestry systems have an important role to play in reducing ammonia emissions and effects. Ammonia impacts occur in the rural environment, so the landscape structure has the capability to buffer these effects.

Under best case scenarios, agroforestry ammonia abatement systems can decrease ammonia emissions by up to 45%.

A note of caution.

It is important to remember that this best case will not necessarily be practically possible or always economically feasible. For new tree planting it will take several years before ammonia recapture would be optimised.

To read the whole study please click here.

05.03.15 Soil, our greatest asset

Along with air to breath and water to drink, soil is one of our most important natural resources. Without it we would starve. However, due to poor farming practices, we are using soil at a completely unsustainable rate. The United Nation’s General Assembly has designated 2015, the International Year of Soils, to raise awareness of the urgent need to switch to sustainable soil management. If we do not make major changes to farming methods, food production will decline in future, instead of rising to meet the needs of a growing population.


To download the image as a PDF please click here.

The information in this blog comes from an article written by Elizabeth Winkler and published by the Sustainable Food Trust. For more information on the SFT and to read the full article, please click here.

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