Inzaai van de boomstrook op het Inagro agroforestry perceel

Digging Deeper: What will we measure for many years?

We are in full preparation to plant our own brand new agroforestry plot! This winter, the trees will go into the ground. Through the 'Digging Deeper' series in our newsletter, you receive a monthly update on our plot and are able to follow the progressions from the front row. What will we measure on our plot in the coming years? What took place on the plot? Read about it in this third edition.

Long-term research as piece of the puzzle

Building an agroforestry system is an investment assumed to pay off only in the longer term. The production of trees obviously takes a few years and a healthier soil, better water management, increased biodiversity,... cannot be achieved overnight. Long-term monitoring is therefore the best way to really appreciate an agroforestry system. But agroforestry comes in many shapes and sizes.

Containing them all in one research plot is impossible. That’s why we made a few concrete but well considered choices for our plot. Practical workability and feasibility are key here. Our plot, which combines walnuts with arable crops (maize, potatoes, winter cereals and field beans) and vegetables (leeks, carrots, cabbages, celeriac), will be subject to long-term monitoring starting this year.

Plattegrond agroforestryperceel

Claims of agroforestry scrutinized

In the first edition of Digging Deeper, you could already read about the many potential benefits of agroforestry for your farm and the environment. Benefits that are usually cited to encourage practice, but at the same time also initiate debate. Through long-term monitoring of a series of parameters on our own agroforestry plot, we want to help substantiate these claims with objective figures. Below, we give a brief overview of what we will measure and how. We look at the plot from an agricultural, ecological and economic point of view.

Agroforestry zorgt voor aanrijking van organisch materiaal in de bodem (c) Consortium Agroforestry Vlaanderen

What are we measuring on the agroforestry plot?

  1. Cultivation: we determine the yield, quality and health of the intercropping on a yearly basis. Because in agroforestry you also have to consider the tree as cultivation, we also monitor the growth, health and productivity of our nut trees over the years.
  2. Microclimate: We install several permanent weather stations and soil and light sensors on the plot and calculate the impact of the trees on parameters such as wind, light, soil moisture and temperature and air temperature throughout the year.
  3. Soil quality: Through annual topsoil analyses, we look at the impact on a set of soil chemical parameters, with a focus on organic carbon build-up. We also count earthworms as an indicator of soil quality annually.
  4. Biodiversity: Using pot traps, we capture and count walking beetles, among others, as natural pest controllers. We also test automatic detection systems to count insects, as well as birds and bats.
  5. Profitability: Over the years, we conduct an economic analysis of the entire system. This includes tree and crop yields, cultivation costs, labour costs, etc. This way we check whether this cultivation system is profitable at plot level in the long term.

Most of these parameters will be looked at in function of distance from the rows of trees, meaning we will be repeating the measurements at different distances from the rows of trees to check how far in the field the impact of the trees extends. Moreover, the set of parameters we are monitoring is not an exhaustive list. Over the years, we also want to implement new insights, develop new research collaborations, test new monitoring methodologies, release new agroforestry models and tools on our plot.

Zooming in on the tree strip

Farmers often opt for a productive use of the tree lane, such as the (temporary or permanent) cultivation of berries or shade-loving crops such as pumpkin, rhubarb, etc. This can help to financially bridge the period when the trees are not yet producing, but also makes the system a lot more complex and labour-intensive. For instance, harvest periods of intermediate crops, trees and tree lane cultivation must be well coordinated. In addition, tree lane cultivation is often difficult to manage or harvest mechanically and you have an extra product to market.

That’s why on our plot, we deliberately chose to sow a perennial grass herb mixture in the tree lanes to serve the intercropping and the tree. These provide an attractive habitat for beneficial insects, such as ground beetles, and require low-intensity mowing management. We chose the perennial mixture offered annually through Inagro’s group purchase (see photo as an example of a perennial mixture along a hedge). Sowing was done in autumn, a few weeks back (see below).

Gemengde heg en meerjarige bloemenrand demoperceel agronatuur

What happened in the field since the last edition of 'Digging Deeper’

A soil-Verisscan already provided some useful maps which nicely visualize the heterogeneity of the plot and can be used in function of future intermediate crops. We also counted the number of earthworms on the plot for the first time. With an average of 90 worms per m², we have a start situation where the density of earthworms is rather low. Currently, there is phacelia and Japanese oats as cover crop on the plot, but in the meantime the tree lanes were sown with a grass-herb mixture under perfect sowing conditions.
For the experts, sowing was done with a combination dent-michel, power harrow and pneumatic seed driller.
And the trees? Those will remain at the plantation still for a few more weeks until the leaves have completely fallen off and they are ready to be moved to Inagro.

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