A ‘fragrant’ agroforestry – Our new cooperation partner Dercks Gartenbau

What does lavender make you imagine? Our thoughts immediately turn to Provence. But there are also small lavender fields here on the Lower Rhine, for example in Geldern-Walbeck at Dercks Gartenbau. The family business has been growing ornamental plants for almost 50 years. Today, in addition to lavender, callunas, spring and summer perennials also grow in the greenhouses and open spaces.

Sustainability in production plays a major role for the Dercks family. For example, the horticultural business has been using precision casting trolley prototypes in outdoor pot plant cultivation for 8 years. In addition to making major savings on the precious resource of water, precise fertiliser distribution is achieved, thereby reducing inputs into the groundwater. The idea came from senior partner Peter Dercks and was realised thanks to his personal conviction.

Agroforestry in horticulture

The idea of inviting Peter Dercks to help shape the transformation of the Lower Rhine in the the future was an obvious one. Since this spring, Dercks Gartenbau has been a co-operation partner of our Agroforstry Living Laboratory transformation project. “The aim of agroforestry systems is to integrate woody plants into agricultural production systems,” explains Samuel Lemmen, who works as a research associate in the Agroforstry Living Laboratory.

“Horticulture is also agriculture, even if it is not traditional field farming. It is very important here in the Lower Rhine region. That’s why it is particularly suitable in this region to implement agroforestry in pot plant cultivation as an example, with scientific support. And to determine how woody plants can be integrated into modern production systems. There is little structural diversity in many production systems. The implementation of agroforestry in pot plant cultivation varies greatly depending on the type of farm. We are therefore all the more pleased that in Mr Dercks we have found a partner who is thinking along with and supporting the necessary change in horticulture with a great deal of idealism and enthusiasm for the environment.”

Horticulture – a special case

The outdoor areas at Dercks Gartenbau are self-contained production areas. A film is laid over a layer of lava stones, which store the water. The areas are meticulously planned. Planting rows of trees in the production area at short notice is an absolute impossible task. For example, the irrigation systems must be able to run unhindered. In addition, unlike in agriculture, deciduous trees in the immediate vicinity of the plants may be undesirable. In traditional agroforestry, foliage is supposed to improve the soil, but in pot plant cultivation, no foliage can be allowed to fall on the already almost sterile production areas. Otherwise there is a risk of fungal infestation, for example, and the products would no longer be marketable. In addition, the introduction of seeds can lead to considerable additional work, especially in the case of wind, as the individual potted plants have to be freed from them. So where is the right location for the shrub to be planted?

Rainwater management

At Dercks Gartenbau, rainwater and excess water from plant irrigation seep away into infiltration troughs next to the open spaces. To compensate for sealed surfaces, every agricultural business must implement rainwater infiltration measures. The Dercks family has created more intake areas of aquifer than necessary, mainly due to bad experiences from past heavy rainfall events. These are currently covered with grass and weeds. According to the regulations of the Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau e.V. (FLL), planting with woody plants is not intended.

Samuel Lemmen finds this hard to understand: “Trees in infiltration swales can ensure faster infiltration, as the soil is loosened by the tree roots. There can also be a filtering benefit, whereby excess water from irrigation, some of which also contains fertiliser, is absorbed by the trees and other plants. For him and Peter Dercks, it was clear: “The infiltration dips are ideal for an agroforestry pilot project.”

Together with Regina Bach, who is the liaison between Rhine-Waal University of Applied Sciences and Agrobusiness Niederrhein e.V. for our project, they did some research, exchanged ideas with stakeholders such as the Chamber of Agriculture of North Rhine-Westphalia and engineer Barbara Dröppelmann from the planning office for landscape and environment in Geldern, wrote applications and can now be pleased: The Lower Water Authority of the Kleve district has granted approval for the use of an infiltration trough for the creation of an agroforestry system. The prerequisite for this is scientific monitoring by HSRW researchers and close dialogue on the findings. The good cooperation between the Agroforestry Living Laboratory and Mr Dercks will be continued: Over the course of the project, for example, soil samples are to be taken, infiltration tests carried out and filtration benefits tested.

Olives and lavender

Peter Dercks aims to plant the tree strips this very year. He decided in favour of olive trees. The evergreen plant sheds its leaves, which are several years old, regardless of the season. The silver-grey leaves are small compared to the leaves of other trees. Moreover, the olive tree is a deep-rooter. The 30 or so trees will be planted around five metres apart. To allow more light to enter, the olive trees will be planted in staggered rows.

Lavender is to grow on the approximately five metre wide strips between the rows of trees and complement the Mediterranean appearance of the agroforestry. The blue-violet flowers serve as a revitalising element and for insect diversity. The reality of horticulture is that ornamental plants go on sale before they flower. The flowering lavender fields mentioned in the introduction therefore do not actually exist.

In Dercks Gartenbau’s agroforestry, you can hopefully experience them on a small scale in the years to come. A small economic benefit that can result from the agroforestry is the pruning of cuttings from the lavender plants. And the future agroforestry also has a very practical benefit: it is intended to provide some relief from the prevailing dry easterly winds.

Regina Bach and Samuel Lemmen also see the collaboration as a model. Their hope: “Perhaps in a few years’ time we will move away from the conviction that woody plants and infiltration swales cannot go hand in hand. And in this way, more diversity and closeness to nature can also be ensured on production farms.”