Digging Deeper: This is where the future of our agroforestry plot grows

We are in full preparation to plant our own brand new agroforestry plot! This winter, the trees will go into the ground. That's why we started our new series last month: Digging Deeper. Keep an eye on our newsletter for a monthly update on this plot and follow our journey from the front row. What tree species did we choose and what cultivation rotation did we apply? What does the planting plan look like? Which preparations took place last month? Read all about it in this second edition.

Deciding on tree species: don't make hasty choices!

The first question a farmer with agroforestry plans usually asks himself is which trees would be most suitable for his system. Not an easy question, as there are a lot of things to take into account when making this decision. Always start from the location (climate, soil, wind, etc.), then determine the purpose of your trees (wood, fruit, windbreak, etc.) and then check whether this is compatible with your company-specific situation (intermediate crops, available machinery, size and location of the plot, etc.). A well-considered choice at the start is crucial to earn back your investment in the long run, so inform yourself thoroughly!

Inagro opts for walnut

The final choice for the agroforestry plot at Inagro was walnut (Juglans regia), a versatile tree species interesting in both economical and cultivational terms. The wood and nuts (along with derivatives such as oil and liquor) are high-quality products with a good market value. Walnuts are still mainly imported from southern Europe and America. The growing focus on local production (as well as local plant protein production) and the increasing number of winter hardy varieties offer increasing opportunities for walnut cultivation in Flanders.

In terms of cultivation, walnut is also very suitable for application in agroforestry. Most varieties tend to stay low, have an open crown, come into leaf relatively late and lose these again early in autumn. This ensures that competition for light with intermediate crops is rather limited. Leaves of walnuts are also nutrient-rich and break down quickly, providing natural nutrient enrichment in the soil.

Bigger is not always better

We chose Juglans regia 'Broadview', a variety that is standardly available in our region and does well on most sites. Broadview is a self-pollinator and the nuts are suitable for direct consumption or for drying. The smaller size of this variety (8 to 10 m after 12 years) also makes it interesting for use in agroforestry. When purchasing planting material from the grower, we made sure that the trees were not too large yet (here 2 years old, trunk circumference 8/10 cm and 1.80 m high) and were delivered with bare roots. This is not only cheaper, but offers the greatest chance of successful planting.

The picture on the right shows the saplings at the cultivator. These are ready to move to our site in Beitem soon!

Planting plan

Planting an agroforestry plot obviously goes beyond the choice of trees alone. Consideration must be given to the location of the trees in the field (distance, orientation, density, etc.), the crops that will be combined with the trees, the filling-in of the zone under the trees, etc. We also must not lose sight of workability and profitability. Time to explain our planting plan In detail.

'Alley cropping' as a modern form of agroforestry

For our plot at Inagro, we opted for an 'alley cropping' system, where rows of trees in the field alternate with the cultivation of agricultural crops. An 'alley cropping' system consists of three large zones that we fill in as follows:

Walnut tree rows are rather oriented north-south. As a result, shading on the intercropping is minimal. The distance between the tree rows is 24 m, which is about twice the height of the mature trees. By not tying the tree rows to the plot edge, the plot also remains easily workable. Planting distance of the nut trees in the row is 8 m. In total, there is room for 50 trees which amounts to a planting density of about 35 trees per hectare.
As intermediate crops, we use a 6-year rotation of potato, celeriac/carrot, maize, leek/cabbage, winter wheat and field beans. The cultivation zone between the tree rows is 21 m wide, so we can still work with our widest tools, in this case the spraying boom.
Below each row of trees, there is a 3 m wide tree strip on which we do not cultivate but sow with a perennial herb mix to attract pest-resistant insects.

On the western side of the plot, we plant a mixed hedge perpendicular to the dominant wind direction (SW) and thus ensuring wind deflection. The hedge is flanked by a rough grass strip that attracts pest controller insects and facilitates future management of the hedge.

What happened on the field since the last edition of 'Digging Deeper'

Although we are still mostly in the planning phase at the moment, there was some activity on site last month. For instance, we had a Veris soil scan carried out. This scan gives us a detailed map on which we can read conductivity, acidity, organic matter content and soil height for the entire plot. We also drew out the plot and prepared the tree strips so they are ready for sowing. Now we just have to wait for the ideal weather conditions for sowing.