This year, Delphy is continuing its research into the use of various peat-free potting soils based on local waste streams across a number of new crops.
The waste streams range from different types of compost from the Boskoop region to various cultivated fibres. The trial forms part of the European Interreg project CloseCycle, in which international partners are collaborating on closed-loop raw material cycles.
Trial design 2026
In 2024 and 2025, good cultivation results were achieved using the various materials and mixtures with the relatively easy cultivation of Thuja in 3-litre pots. The design for this year has been adapted. This year, we are investigating fewer different mixtures but focusing on several crops that are more difficult to grow. Cultivating these crops in an alternative mixture is more challenging due to root sensitivity, salt sensitivity and moisture requirements.
The following plants have been potted up:
- Hydrangea macrophylla due to its moisture requirements
- Viburnum tinus due to root sensitivity and salt sensitivity
- Astilbe due to its moisture requirements and salt sensitivity
A peat-free mix containing 20% green compost (RHP-certified) has been chosen as the standard. This is being compared with two similar mixes: one containing 20% local organic waste compost (Keurcompost A) and the other containing 20% RHP-certified organic waste compost.
In addition, we are using Miscanthus and fermented Silphie as cultivated fibres.
The local substrate mixture also incorporates the coarse fraction of cattle manure and dried dredged material from the ditch.
Viewing the trials during open days
The plants were potted into 3-litre pots a few weeks ago. During the growing season, there will be various open days for interested parties to view the trials.
Keep an eye on the events calendar on our website www.delphy.nl for the dates!
