A new research paper, “Effects of Controlled Drainage with Subirrigation on Nutrient Concentrations in an Agricultural Field in the Netherlands,” has been published with contributions from FARMWISE partner Wageningen University & Research, together with KWR Water Research Institute. The study takes a close look at how Controlled Drainage with Subirrigation (CD-SI) systems affect nutrient concentrations in soils and water.
What is CD-SI and why does it matter?
Unlike conventional drainage, which is often managed externally by water authorities, CD-SI allows farmers themselves to regulate water levels through a control pit linked to underground drainage pipes. In wet conditions, water can be discharged efficiently; in dry periods, subirrigation enables additional water to be supplied back into the soil, improving crop resilience.
But these changes in water flow can also influence how nutrients move through the system. To understand these dynamics, researchers compared nutrient levels in a CD-SI field with those in a nearby reference field without drainage.
Key findings
Continuous field measurements over eight months revealed several important patterns:
- After manure application, nutrient concentrations in groundwater were higher in the CD-SI field, indicating that drainage management can affect nutrient retention and movement.
- During subirrigation, nutrient levels in the field reflected those of the irrigation source water, showing the need for careful monitoring of water quality inputs.
- Surface water downstream was not impacted by CD-SI discharge, suggesting the system does not automatically lead to contamination.
- Nutrient levels varied depending on proximity to the subirrigation pipes, pointing to localised effects of the drainage infrastructure.
Why it matters for practice and policy
For farmers, these results highlight both the opportunities and the responsibilities of using CD-SI. The technology can secure water availability during increasingly variable weather, but it requires close attention to nutrient management to avoid unwanted impacts on groundwater.
For policymakers, the study provides evidence to guide sustainable water strategies—showing how CD-SI can be deployed in ways that balance agricultural productivity with environmental protection.
As part of FARMWISE, this research underscores our commitment to advancing practical, data-driven tools for sustainable water and nutrient management. By connecting detailed scientific analysis with real-world application, the project helps ensure that innovations like CD-SI can be taken up effectively across European agriculture.
