An introduction to agroforestry: How trees and hedgerows can build farm resilience
At Regenerate Outcomes we believe that trees and hedgerows can play an important part in benefiting soil, plant and animal health on farms.
It was fantastic to be able to bring together a panel of experts this month for the latest in our autumn and winter webinar series: An introduction to agroforestry.
We were joined by:
• Peter Leeson, Woodland Creation Adviser for the Woodland Trust, who talked through why farms should consider agroforestry
• Dr Allen Williams, from our mentoring partner Understanding Ag, who introduced the 6-3-4 soil health framework in the context of agroforestry
• Agroecologist Edd Colbert who explored different agroforestry design options for farms
First up, we heard from Peter, who has spent 30 years working to restore trees and hedgerows on farms.
Peter also publishes a regular podcast, Tree Amble, where he talks to people he has met along the way.
"I'm a real advocate for trees, but they have to add value to our farm systems and when we put a tree somewhere, we need to make sure it's in the right place,” he says.
"My practical simple definition of agroforestry is that it's about adding woody matter to a farm to aid its productivity.
“It’s not just about trees being pretty, it’s not just about biodiversity, although that’s important. It’s about how a farm can take a tree, or hedge or whatever it is and add value to the farm.”
“That might not be the technical definition of agroforestry, but for me, it works because it means that if we're adding trees into a farm system, we're thinking about adding value to that farm.
“It's not just about trees being pretty, it's not just about biodiversity, although that's important. It's about how a farm can take a tree, or hedge or whatever it is and add value to the farm.
"What's interesting is that farms have always had woody material on them. We've reduced that over the years by mechanisation, but trees have always formed a big part of farms historically.
“They would have been used in the past for timber for burning, for making implements with, for hurdles for hedge laying and all sorts of different purposes.
Peter Leeson: ‘The need for trees and woody material on farms has never been greater.’
“Now we're moving into a space where we're thinking about carbon sequestration and water stress, both in terms of too much water and too little.
“We're looking at the impacts of soil loss, fertiliser loss, ammonia loss from farms and thinking about how we might use woody material to actually combat some of those.
“In a sense, that need for trees and woody material on farms has never been greater. But we've had to reinvent the science and the thinking behind that.”
What benefits can agroforestry offer to farms?
Shade and shelter for animals
"This is critical for animals in terms of their well-being, particularly in a climate where we might have really long, dry, hot summers. Cattle are particularly prone to problems in very hot conditions.
"A project at Bangor University looked at shade and shelter and the benefits to animals. It found that animals either in a really warm field in hot sunshine, or on a cold wet day in North Wales, are using 10 to 15% more energy in either staying warm or keeping cool.
“The effect on cattle of not having shade and shelter is significant; it will add to loss of fertility, loss of condition, poor yield and body condition. Climate change may be the best reason why you need to think about putting trees and hedges back into your farms.
Browse
“With shade and shelter comes browse. Leaves provide animals with roughage, sugars, protein, dry matter and in some cases they can provide just as much, if not more, than grass.
“Multiple people have been looking at the additionality that hedges and tree leaves can bring to browse for animal health.
“With leaf browse that additional fibre going into the animal will help them increase the intake of nutrients and sugars from the grasses. So fibre is really important to animal health and well being.
Seasonality
"Where you've got shade and shelter, you've got wind reduction, and different soil makeup because of tree roots. You can have additional seasonality in grasses, which may well make the difference between your animals going into a shed several weeks earlier or later.
“The Woodland Trust has been working with the Pontbren upland farming project in Wales, where the farmers set out to change the landscape so they could rear their lambs outdoors.
“They put loads of shelterbelts back into the landscape and changed the nature of the sheep breeds. What they found was that the shelter belts and hedges extended the seasonality in the grasses near to them.
Soil health
"Agroforestry systems tend to have a lot less issues related to compaction because of tree roots going down and breaking up soil panning with additional earthworm activity. The aeration around tree roots can also open the soil up for water management and better water circulation.
"It reduces the effects of compaction and adds value by taking that water down to the ground where we need it in hot summers.
"We now know there's a relationship between tree roots, plant roots, mycorrhizal fungi and how nutrients and soil moisture move through the ground. These have only really become acknowledged in the last few years and we've now got the computing and the science behind that to actually identify what these processes are.
Soil fertility
"Soil fertility is aided and abetted by plants such as alder, which is naturally nitrogen fixing and has nodules on the roots that fix nitrogen from the atmosphere into the ground.
“Also the leaf fall and leaf transfer is basically taking nutrients from really deep in the soil through the tree up into its leaves, which are then dropped onto the soil surface to be taken into the soil if you have a healthy earthworm population.
“Hedgerows are also fantastic at keeping soils where they should be on fields, particularly in extreme situations. They’re also fantastic in disrupting the loss of fertilisers and fertility from fields.”
“I know lots of farmers now that go out with a spade and regularly count their earthworms. Ideally they’re looking for 20 earthworms per big spade. If you've got that then you know that nutrient cycling is happening.
"Hedgerows are also fantastic at keeping soils where they should be on fields, particularly in extreme situations. They're also fantastic in disrupting the loss of fertilisers and fertility from fields.
"We've been working with farmers on putting hedgerows into the pathway of watercourses to reduce the flow and to store water.
“But we've also noticed that there's increased soil percolation around hedges and that's helping in drought conditions, it’s just the same for grasses.
Pests
“What organic farmers are doing and regen people are doing is looking at whether by increasing the biodiversity of trees and other plants on farms we can actually increase the beneficial pollinator pest relationships. There's a lot of research now saying that that is possible.
“So the more diversity you have, the more likely you are to have things like ladybirds coming in and eating your aphids, for example.
“You've got increased bird populations, and they're going to be coming in and taking caterpillars. In many cases that's becoming critical for people that don't want to use pesticides.
Agroforestry in arable farming
"We've got lots of people we've worked with over the years who have added fruit trees into arable systems, or nut trees, or even strips of productive woodland, alternating rows of productive woodland or nut trees or fruit trees with combinable cropping.
“There's always going to be a machinery issue there in terms of how you plant your trees so that you can still crop effectively and efficiently, but people are doing it and what they're finding is that there is better water management under trees.
“That can be through either reduced transpiration of the crop and water loss where you've got wind speeds which are reduced, or it could be through increased water retention in soils and increased percolation.
“The way a tree root works is that it goes down deep, it opens up the soil beneath you and works with the mycorrhizal fungi and transports moisture and sugars away. But there's always air pockets around those roots and those air pockets allow for the percolation of water down to the soil and act as temporary reservoirs.
“Water tends to be drawn down by tree roots. Many people think that trees will dry out land, and in some cases they can certainly help with that. But trees are not designed to leave themselves in a desert they actually designed to store and manage water.”
Building resilient farms
Regenerate Outcomes is working with farmers across the country to build resilient farms by improving soil, plant and animal health.
Get in touch to find out how we can work with you.