Walnut silvopastoral systems

The following varieties show promise in the UK:

• Lara
• Jupiter
• Fernor
• Fernette Geisenheim 139

It is best to plant a mixture to ensure good pollination. It is also useful to plant Franquette due to its excellent taste and because it is commonly used as a marker for the phenology of flowering e.g., variety X bears female flowers Y weeks after Franquette. For a full list of walnut varieties see Crawford (2016).

Grafted trees 1 to 2m can be planted at a density of 100 stems per ha and need to be staked with 2m stakes. Ideally two are used to support the tree. Protection may be required from sheep.

Mulch is used to stop grass growth around 1m radius of the planted tree. Most graziers use mowers to control thistles so it may be useful to change the spacing of the tree planting to allow mowing. The exact measurements will depend on the width of the machines.

The planting arrangement that would provide 100 stems per hectare would be 5m x 20m. It is best to prune away lower branches during the first 10 years and leave 4 to 6 main framework branches in a goblet shape. Walnuts will benefit from fertilisers (N+P) and irrigation.

There are no major insect pests of walnut in the UK and diseases such as leaf blotch (Gnomonia leptostyla), blight (Xanthomonas arboricola pv. juglandis) and honey fungus (Armillaria spp) can be prevented or reduced by removing leaf land branch litter.

Working at the landscape scale offers the greatest potential for the delivery of optimised ecosystem services. Areas of walnut agroforestry can be used to remove phosphate and nitrate annually as nuts contain high levels of phosphorus and nitrogen.

Conversion of arable areas into silvopastoral systems linked to tree roots blocking land drains could help to increase carbon sequestration and improve biodiversity linked with meadows and wetlands. Riparian planting could also serve to reduce river pollution. It is also important to check whether your land is designated or a priority habitat, as planting these trees may not be appropriate for all sites. At this scale it is very appropriate to consider forming a tripartite environmental partnership consisting of:

1. a grower
2. a government agency or utility, and 
3. a private sector philanthropic entrepreneur/broker

A 25-year environmental stewardship contract could deliver decontamination, biodiversity, carbon offsetting, and or green infrastructure benefits (e.g., reduced flooding).

The gross margin data presented focusses on the tree component only. The wide spacing of the trees and the moderate beneficial shade cast means that a target of 100% intercrop yield is expected on average over the life of the system. Beneficial interactions mean that in many cases the loss of the land area under the tree strip is totally compensated for.

Tree density: 100 per hectare 
Target average yield (tonnes): 3.5 per hectare¹ 
Price per tonne: £15,000² 
Total Output: £52,500

Variable Cost (£)

Orchard depreciation (establishment): £840³ 
Pruning/clearing: £50
Organic fertiliser/sprays: £81
Crop sundries e.g. tree ties: £20
Harvesting (labour): £200⁴ 
Processing: £500
Storage/ bin hire: 0
Packaging e.g. boxes: £111
Transport: £90
Marketing and sales: £100
Commission/levies: 0
Total variable cost: £1,992

Tree crop gross margin: £50,598

The gross margin of £50,598 per hectare for the walnut component compares to £1,335 for high yields of milling wheat and £13,052 dessert apples as outlined in Nix (2023).

Notes

1. Based on full crop data in Crawford averaged over the life of the orchard (2016)
2. Assumes a high value product e.g., English walnut oil. It is not a wholesale price and bears no relation to global prices
3. Over 5 years based on the life of the establishment materials (tree guards, and stakes etc) and not the life of the tree
4. This is the only labour that is contracted. All labour for other operations is assumed to be farm staff which is part of the fixed costs of the operation

Major nurseries are now selling grafted walnut trees and can give advice on varieties.

Walnut is also suitable for silvoarable systems and forest gardens.

Hampshire County Council have created a new Facebook group, The Hampshire Agroforestry Forum, to enable farmers, growers, and food entrepreneurs to link with each other to facilitate new markets for tree products. If you have products to sell or you are looking for products produced from trees, please add your details to the group. You could also pose any questions and queries about agroforestry for others to answer.

Walnuts require sheltered sunny sites (avoid excess shade which can affect the quantity and quality of any nuts produced) with deep soils e.g., sandy loam with a pH between 6 and 7. Sites should have good drainage. Very wet soils with heavy clay are to be avoided. Avoid valley bottoms or landscape dips as frosts may linger which can damage walnuts in spring.

Nuts will fall to the ground and livestock should be removed one week before nut fall. There are several simple hand-held roller harvesters on the market. Nuts should not be allowed to stay on the ground for more than 48 hours and should be de-husked, cleaned and dried.

Most growers would see income from the trees as the main purpose of the venture and this can be substantial.

A high yield scenario based on global experience of countries with a similar climate gives the start of nut bearing in year 3 with 1kg per tree. At year 10, 10kg per tree is obtained. At year 25, 52kg per tree is obtained as in Crawford (2016). The model is based on 100 stems per hectare. A conservative and simple target for yields of walnut in agroforestry in the UK could be 3.5 tonnes per hectare averaged over the life of the trees. The productive life of the trees could be over 50 years depending on management and site. Additional income streams are possible from grazing, environmental stewardship, and any remaining tree biomass. Shell by-products are an exciting area to consider moving forward, with applications in mulching, fertilisers and even hand creams.

Experience shows that 100% grazing income is possible for the whole rotation as at 100 stems per hectare, shading is minimal. Benefits to livestock include reduction of high and low temperatures due to shade effects.

Walnut products derived from UK crops should be viewed as a premium product and not compared to imported goods. For instance, fresh in-shell nuts have a milder taste and may have greater health benefits than many imported nuts. Fresh nuts will have higher levels of vitamin C than dried nuts for instance. Eventually, as the production increases there will be increased prices paid for the crop if it is labelled as a product of designated origin (PDO).

It should be noted that most walnut veneer for luxury cars now comes from Juglans regia grown for the nuts in commercial orchards in the USA. Figured timber (interesting grain pattern for using as veneer) only occurs however in about 0.1% of the trees and the reasons for the figuring are not fully understood. Valuable timber is a possible by-product of UK walnut orchards, but any financial assessment should be based on the nuts alone.