Circular-nutrient nature-based solutions in the Limfjord catchment (Denmark)

The catchment covers ~260,000 ha, ~63 % of which is agricultural land. The site partly spans the national range of biodiversity scores (0-16, where 20 is highest nationally) and nitrogen retention percentages (5-100 %). The land use resembles Denmark’s national average. 

To test targeted, innovative nature-based solutions (NBS) in a representative Danish agricultural catchment to support the socio-ecological transformation of nutrient management — especially nitrogen (N) losses — through a systems approach (field/local, farm, landscape, regional). 

In Denmark, large-scale land-set-aside is not seen as a plausible option because it would compromise agricultural economic profit. Therefore, stakeholders emphasise the need for targeted and innovative NBS with stakeholder involvement. The Danish team adopts a systems approach to define, monitor and assess NBS effects from field to regional scale. 

The site is part of the EU-funded Horizon Europe trans4num project. 

The catchment faces a national coastal nitrogen reduction goal of approx. 13,000 ton N/year by 2027; ~28 % of this is to be reduced from the Limfjord catchment and half of that (~1,500 ton N/yr) from the chosen NBS site. 

The proposed interventions (e.g., perennial grass/clover rotations, bio-based fertilisers) are expected to reduce nitrogen leaching, improve nutrient balances, increase nutrient circularity, reduce mineral fertiliser dependency and support farmer profit while benefiting the aquatic environment. 

The trans4num Danish site selected two main NBS interventions:

1. Changes in crop rotations: Moving towards more biomass crops including perennial crops (e.g., grass production, grass-clover mixtures) for biorefinery purposes (protein for monogastrics, fibre for ruminants). This replacement of cereals with grass influences field/crop rotations, farm nutrient balances, local climate accounting, and potentially benefits surrounding nature and aquatic environments.
2. Use of bio-based fertiliser from organic waste: Using manure and other waste streams instead of chemical fertiliser to increase nutrient circularity and reduce nitrogen loss while enhancing farmer’s profit. 

The site is designed to be representative for the Danish region and its land‐use, biodiversity and nitrogen retention ranges. The approaches (biomass crops, nutrient circularity) demonstrate practices that could be transferred to similar intensive agricultural systems in Northern Europe

Early findings from Year 1 show that grass-clover rotations reduce nitrogen leaching and maintain yields; field testing in Year 2 confirms this and shows improved nitrogen balances and reduced mineral fertiliser dependency when bio-based inputs are integrated. The regulatory sandbox approach supports real-world testing of nutrient-management policies with stakeholders

Klimafonden Skive, Innovationscenter For Okologisk Landbrug, Cordulus, Aarhus Univeristy, Dept. Of Agroecology

1. KLIMAFONDEN SKIVE

amsl@klimafondenskive.dk

Anne-Mette S. Langvad

2. INNOVATIONSCENTER FOR OKOLOGISK LANDBRUG

anto@icoel.dk

Anton Rasmussen

3. CORDULUS

md@fieldsense.dk

Morten Birk

4. AARHUS UNIVERISTY, DEPT. OF AGROECOLOGY

tommy.dalgaard@agro.au.dk

Prof. Dr. Tommy Dalgaard

The chosen Danish NBS site is situated in Northern Jutland and represents part of the Limfjord catchment, which connects the North Sea and the Kattegat and covers an area of approximately 260,000 ha where about 63 % is agricultural land. The land-use of the site resembles the national Danish pattern and partly covers the national range of biodiversity scores (0-16) and nitrogen retention percentages (5-100 %), making it representative for the region.