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New geophysical technology paves the way for a cleaner aquatic environment

Within a few years, it may be possible to better target the use of nitrogen by agriculture. Research at Aarhus University has resulted in a concept for mapping the geological strata of individual fields, which is one of the unknown, but important, links in understanding how nitrogen flows from field to fjord. Learn more about the research in the podcast below (in Danish).

2019.08.30 | Dorthe Lundh

A woman and two men stand behind a red all terrain vehicle (quad bike) on a yellow field.

Headed by Esben Auken (centre), researchers at Geoscience are testing the new technology in a field west of Aarhus. Here seen with a key collaboration partner in the project, Irene Wiborg from SEGES (agricultural consultancy), and postdoc Pradip Maurya, who is preparing the measuring equipment for the test. Photo: Dorthe Lundh

A man is riding the quad bike on a field, towing two sleighs with transient electromagnetic measurement equipment, while a man and a woman are standing in the background.

Preliminary research results show that geophysical measuring equipment towed by an ATV can map out the subsurface and thereby identify where fertiliser from agriculture risks spilling into the aquatic environment. Photo: Dorthe Lundh

Researchers at Aarhus University are working hard to generate new knowledge and develop sustainable technology to help create a greener future for business and industry and for society at large. In the Bæredygtig Viden (sustainable knowledge) podcast series you will meet researchers who think outside the box and who work together across disciplines and with businesses to find solutions to the world’s major challenges.

For a number of years, researchers at the Department of Geoscience at Aarhus University have been involved in identifying and modelling subsurface water bodies in parts of the world affected by drought. By loading helicopters with equipment developed at the department and overflying large areas, the researchers have delivered low-resolution models of the areas’ geological layers, helping government agencies and the general public in countries like India and the US.

However, in recent years, the research projects rOpen and MapField have made it possible to refine the geophysical technology and target it for use on ground. The new solutions can help to balance agriculture's use of nitrogen, benefitting both food production and the aquatic environment, and thus contributing to greening of the agricultural sector. 

"The geology differs from field to field. With the new technologies, we can perform high-resolution surveys allowing us to estimate with fairly detailed accuracy how much fertiliser will be converted in the root zones of the plants in the individual field, and to identify areas that don’t convert the nutrients as effectively but lead them away and into the aquatic environment," explains Esben Auken, professor at the Department of Geoscience, Aarhus University, and head of one of the two research projects. 

Precision fertilisation

The current project results therefore point to the prospect of being able to identify areas with the greatest risk of nitrate spreading to the aquatic environment. This will make it possible to apply fertiliser in dosages that can be absorbed by the crops, thus sparing our waterways and inlets from excess nutrients.

"We’re in a situation where, based on our two major test areas, which are located in two geologically different areas in Denmark, we can make fairly precise estimates. That's why we're now scaling up to more areas," says the professor.

He believes that the research results from the MapField and rOpen projects can be used commercially within just a few years.

Electromagnetic smoke rings

The research teams of the projects use what is known as the transient electromagnetic measurement method to map the geology of the fields. An off-road four-wheeled motorcycle, ATV, tows the measuring equipment along the spraying track in the field.

"We're sending a strong electromagnetic pulse through the ground layers for only a few hundred-millionths of a second. The pulse is generated with a current of up to 30 amps, reaching up to 100 metres down and moving like a smoke ring. With our highly sensitive instruments, we measure in just about a thousandth of a second how quickly the impulse decreases. Then we reverse the current and repeat the process. Depending on how we configure the system, we make between one and two thousand measurements per second while travelling the field. Based on the vast amount of data we collect, we can draw a picture of what the soil layers look like," Esben Auken explains.

Interdisciplinary approach – also at the workshop

The measuring equipment and instruments are made at the basement of the Department of Geoscience. Here, a team of various academic background and expertise work in the department's workshop. There are experts e.g. from the disciplines of engineering, computer science, geophysics and geology, who design, test and continually adapt the equipment that will be used in the research projects.

Not only here, but in all aspects of the research carried out at Geoscience, interdisciplinary collaboration is crucial for reliable, applicable and financially viable solutions, emphasises the professor:

"We work in interdisciplinary consortiums consisting of a number of institutions, companies and researchers from AU, the University of Copenhagen and GEUS, as well as other large institutions. In rOpen alone, the project that has developed the concept for surveying the subsoil of farmland, we have 13 partners," he says.

SEGES a key partner

One of the key partners in the projects on the aquatic environment and agriculture is the SEGES Innovation centre, which provides specialist advise and solutions for the agricultural sector.

"SEGES is an important partner because they are in contact with farmers and agricultural advisers, and because they also communicate with ministries and interest groups," says Esben Auken.

Head of section Irene Wiborg is the representative of SEGES in both rOpen and MapField. She agrees that SEGES’ role as a partner in the projects is important.

"We see it as our job to work collaboratively with the other partners. We are very pleased to be working with Geoscience and GEUS. They have a unique knowledge of the subsoil and nutrient subsurface flow patterns. This can make us wiser about where it may be necessary to make changes to cultivation practices and possibly take some areas out of production in order to protect the aquatic environment, which is so important to Denmark, and which we all want to protect. This should be achieved in a way that allows farmers to continue to make a living from producing food," says Irene Wiborg.

She emphasises that the project results also have significance for how we can live up to the EU Water Framework Directive.

"There’s a great need to develop new technologies. If we don’t, it will be difficult for us to meet the Water Framework Directive’s requirement for the aquatic environment in Denmark to have a ‘good status’ by 2027. For this reason, too, SEGES is dedicated to finding solutions that prevent more nutrients from spreading to the aquatic environment," she says.

Broad perspectives

However, the perspectives for application of the new technologies go far beyond the agricultural sector. They can also be used to map pollution from the chemical industry, to provide solutions to prevent damage from heavy rainfall, and to plan new developments for residential homes, just to highlight a few.

A new project in collaboration with the Poul Due Jensen Foundation is currently being implemented in its initial phase:

"In a couple of months, we’ll be shipping equipment to Tanzania that will help to identify the best place to establish local water wells, so that women don’t have to walk for hours to collect water. If we’re successful, it will mean a huge difference for the local population," predicts Esben Auken.

Further information

Please read more about rOpen, MapField and other of HydroGeophysics Groups projects at the homepage of the Department of Geoscience.


Professor Esben Auken,
HydroGeophysics Group,
Institut for Geoscience
Aarhus Universitet
Mail esben.auken@geo.au.dk
Mobil 2899 2587

Afdelingsleder Irene Wiborg
Mail iaw@seges.dk
Mobil 3092 1733