The Irish Agroforestry Conference 2021 PART 2

Several weeks ago, Clive Bright of the Organic Trust reported from the first day of the Irish Agroforestry Conference. You can read about that here. In this article he summarises the presentations of two more noteworthy practitioners of Agroforestry.

Establishing Agroforestry within Horticultural Cropping 

Day two of the Agroforestry Conference opened with a fantastic presentation from Andy Dibben, who is head grower at Abbey Home Farm (660Ha) in Gloucestershire, wherein he manages 6 hectares of organic vegetables, which supplies their café and farm shop.

Andy began his working life as a coppice worker, hedge laying and charcoal making, where he developed his love for trees. He moved to a job in horticulture and progressed through the ranks to become a head grower. He says adapting to climate change is the main advantage of including trees in any food production. Wind shelter, drought, and heavy rainfall events are the primary concerns. Well-planned tree planting will reduce wind, protecting against plants being physically damaged and flattened. It will also reduce the drying effect and evaporation in drought and, therefore, less irrigation is required. Trees will keep the micro-climate warmer which increases yields and allow for earlier crops. Crops will also benefit from the nutrients being recycled from deeper in the soil by the tree roots.

Together with advantages to the horticultural crops, trees also allow for the added production of top fruit (apples, pears and plums), and woodchip to produce mulch and compost which along with cover crops, are the only sources of fertility building on the farm. There are many competitive benefits to encouraging wildlife into a cropping area. Everything from creating perches for birds of prey that manage rabbits, songbirds eat caterpillars, pollinating insects and predatory insects like lacewings, hoverflies and slug eating ground beetles all play their roles. “It is not a question of being charitable to wildlife; they are all tools for the organic veg grower.”

When it comes to production of woodchip for compost and ramial wood chip, Andy favours alder and hazel. “Although willow is famed for its ability to produce biomass, hazel or alder will make the same amount of biomass over a twenty-year period because they are heavier woods. Hazel and alder are not thirsty trees like willow can be, so they focused on planting them”. Andy revealed that earlier potatoes drills between willow failed as the willow removed the moisture from the soil to the detriment of the spuds. However pussy willow, positioned away for the cropping area, are chipped to mulch the apple trees because research has shown that willow chip has a preventive effect on apple scab. To save the time and energy of making compost from all the woodchip, they spread much of it as ramial (small-diameter fresh woodchip) on their cover crops.

The shading effect of trees may not be an issue for pasture, but in vegetable cropping, it is, so they laid out the site with a North to South aspect. The tree row understorey strips are designed to be quite broad, 4.5m, to allow for the final canopy. The edges of that 4.5m strips are ploughed 20cm deep to prune the tree roots and drive them down below the depth of the veg crops. The tree rows are designed to suit machinery, irrigation equipment, multiple 1.5m bed widths and be an effective windbreak managed at 5m high. 50m between tree rows best fit all the criteria. Within the tree rows, an apple is planted every 28m, with seven trees planted in between, alternating a species of coppice tree with a species of wildlife tree.

The most interesting bit is how the coppicing cycle is integrated with the five-year vegetable rotation. The hazel and alder are also on a five-year coppice rotation that gets up to 5-6m high, at which point it has the greatest shelter effect. At this stage, Andy plants his two-year fertility-building break-crop. He maintains that establishing this crop is vital to the garden’s success, and shelter from drying winds is crucial. In year two, when the fertility crop is well established and doesn’t need wind protection, the trees are coppiced and chipped. This ramial chip is applied to the living cover crop, which aids its breakdown and boosts fertility. In year three, mixed brassicas are sown, these are wind hardy but have a little shelter from the first year’s growth. In year four, it’s alliums; they don’t need much wind protection as a crop, but because they cast no shade or soil cover, wind protection is important to reduce the soil moisture evaporation. In year five, with 3-4 years of coppice growth, winter squash and sweetcorn are well protected, and that rotation repeats with the break crop.

Andy’s next plan includes bringing Agroforestry into the new 1000m2 glasshouse. To conclude, Andy wanted to drive home the message that while trees provide lots of longer term benefits the positive impact on biodiversity is almost instantaneous. “Birds will use the branches, insects will feed on the blooms, and the fungal networks will develop in the soil within the first year”.

Hells Kettle Farm in Wicklow
Gavin Lynch of Hells Kettle farm in Wicklow, situated 220m above sea level, grows 4 acres of hazelnut orchard on his dairy enterprise. The primary objective is to produce hazelnuts, but orchards have a dual role of being a “nursery for the dairy calves” for 6-8 weeks early in spring. The roots of the trees and the shelter they provide create a dry, protected space with early grass. When the hazel trees begin to leaf out, the calves are moved, so they don’t browse the trees.

Gavin has also kept turkeys under the hazels in the autumn. They provide shelter, a broad diversity of grubs and insects, and late-season grass and leaf fall. He found it was an economic space to raise the birds and that “they seemed to love it in there.”

He grows 11 different varieties of nuts and advocates for that level of diversity for resilience. The orchard is laid out at standard spacing 4m between trees and 3.8 between rows, works quite well; the bare trees in spring allow plenty of light for early grass growth, but in summer, when in leaf, the trees create enough shade to reduce grass growth so isn’t competing with the trees for moisture. 

Gavin also discussed the ash plantation he planted under the native woodland scheme, which is suffering from ash dieback. He said he would love to manage it as an agroforestry site but is currently restricted by Dept rules. Gavin sees the potential for out-wintering lighter animals or certainly shortening the housing period by rotating them through the thinned ash plantation. He believes that managing this carefully would reduce the cost and environmental implications of housing animals.

Full recordings of the Agroforestry Conference can be accessed at www.nots.ie


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