Joining forces above and below ground to tackle nitrogen pollution

It all started with a casual conversation between Professor Davide Cammarano and Associate Professor Eusun Han at a coffee corner, two researchers whose expertise rarely converges in traditional projects. Precision agriculture and root science are usually studied worlds apart. But as they talked, they realised they might be able to solve the greatest challenge of Danish Agriculture: ground water pollution by nitrogen leaching.

For years, Davide Cammarano had observed a striking pattern in his field-scale measurements: neighbouring areas of the same field can show surprisingly large differences in nitrogen leaching. The question had been on his mind for a long time. Eusun Han, meanwhile, knew from his work that root growth in crop field is strongly shaped by soil conditions, creating substantial plasticity and variation across a field.

As they contemplated this together, the two researchers arrived at a shared idea worth testing:

Could variation in crop root growth be driving the variation in nitrogen losses across the field?

That insight became the spark for the new research project VARIANCE: short for “Managing root–soil–plant spatio-temporal variability to optimize nitrogen use and minimize leaching in sustainable agriculture.”

Funded by the Danish Independent Research Fund (DFF) under the Green Research programme, VARIANCE aims to rethink nitrogen management by uniting what happens aboveground with what happens below to support the green transition.

Beyond the surface

For decades, nitrogen has been both a blessing and a curse. Essential for high yields, it also leaks from fields into streams, fjords, and groundwater, contributing to eutrophication and greenhouse gas emissions. Despite advances in precision agriculture, losses remain high; especially in Denmark’s designated Nitrate Vulnerable Zones.

Davide Cammarano and Eusun Han believe part of the problem lies underground:

“Modern precision agriculture has focused mostly on what we can see from above: drones, sensors, satellite maps, but we’ve ignored what’s below,” Davide Cammarano explains. “Root systems are dynamic,” Eusun Han adds. “They grow deeper or shallower depending on soil type, weather, and management. And that variability changes how efficiently plants use nitrogen.”

By studying how roots vary in depth and density across a real, full-scale field, not a small, uniform trial plot, the VARIANCE project aims to understand how those patterns affect nitrogen uptake and leaching. The project’s 11-hectare field at AU Viborg will host more than 80 measuring points equipped with sensors, root imaging tubes, and suction cups to track how nitrogen moves through soil and into plants.

A digital twin of the field

The project will also develop a digital twin: a data-driven model that mirrors the real field in a computer simulation. By combining root measurements, soil sensors, and remote sensing data, the digital twin will simulate how nitrogen behaves under different conditions.

“In simple terms, it’s like creating a digital mirror of the field,” Davide Cammarano says. “We can then test scenarios: what if we apply less nitrogen here, or if we have a wetter spring there? The goal is to learn enough about variability that we can design smarter fertiliser strategies: ones that reduce losses without hurting yield.”

Davide Cammarano and Eusun Han will integrate this underground insight with cutting-edge modelling. International partners at the University of Padova and Michigan State University will contribute expertise in sensing technologies and model development as well as host young researchers for training stays.

From science to society

While the science may sound technical, the societal motivation is simple: cleaner water, more resilient farms, and a smarter green transition.

“Reducing nitrogen losses is not just about complying with EU regulations,” says Davide Cammarano. “It’s about protecting our natural resources and making sure farmers can keep producing food sustainably. Eusun Han adds: “If we can use roots to guide better management, everyone from farmers to fjords will benefit.”

The project also supports Denmark’s commitment to cut nutrient losses by 50% by 2030, in line with the EU Green Deal and Farm to Fork Strategy. In the longer term, the two researchers hope VARIANCE will inspire new advisory tools for farmers and service providers, helping bridge the gap between complex models and real-world practice.

A new generation of researchers

Beyond its scientific and environmental goals, VARIANCE also invests in the next generation of agricultural researchers. The project will fund a PhD student and a postdoctoral researcher, who will gain hands-on experience in advanced field experimentation, modelling, and international collaboration.

“It’s important that young researchers learn to connect data, modelling, and sustainability,” he says. “The future of agriculture will depend on people who can work across those layers.”

Looking ahead

As the first sensors go into the soil this year, Davide Cammarano and Eusun Han are clear about what success will look like.

“If, four years from now, we can say we understand how root variability shapes nitrogen losses, and we can model that reliably, then we’ve taken a big step forward,” Davide Cammarano says. “Because once we understand it, we can manage it.”

More information

Full title: Managing root-soil-plant spatio-temporal variability to optimize nitrogen use and minimize leaching in sustainable agriculture (VARIANCE)

Funding: Danish Independent Research Fund (DFF) “Green Research” programme: 7.2 million DKK

Principal Investigator: Prof. Davide Cammarano, Aarhus University

Co-PI: Associate Prof. Eusun Han

Partners: University of Padova (Italy), Michigan State University (USA)

Duration: 4 years

Main goals:

• Quantify how root depth and density affect nitrogen leaching
• Develop a data-driven “digital twin” of the field
• Support smarter, site-specific fertilizer practices aligned with EU Nitrate Directive
• Train young researchers in sustainable, data-based agriculture

Contact: Prof. Davide Cammarano, Department of Agroecology, Aarhus University. Tel.: +45 93522545 or mail: davide.cammarano@agro.au.dk