Prestigious medal for soil research awarded to WUR's 'earthworm professor'

Van Groenigen is more of than just an expert on earthworms. In addition to his groundbreaking research, he serves as the editor-in-chief of the soil science journal Geoderma, advocates against fraud and performance pressure in science, and appears in the film "Onder het Maaiveld" (Below the Surface). All these aspects contributed to the decision of the European Geosciences Union (EGU) to award him the Medal.

His research explores the connection between earthworms and chemical processes in the soil, particularly concerning the nitrogen, carbon, and phosphate cycles. The EGU notes, "It is unique that he works at the intersection of biology, chemistry, and agricultural management – all in the context of climate change." The phrase "natural cycles in unnatural soils," the title of his inaugural lecture in 2017, succinctly captures his research focus. Van Groenigen explains, "We investigate how natural cycles can improve an unnatural soil, which is essentially what many agricultural soils are. We examine the role of biota, with the earthworm as a key player."

Earthworms enhance the availability of phosphate and nitrogen

Van Groenigen has effectively highlighted the importance of earthworms. He states, "Everyone knows that worms are good for the soil. But through which mechanisms, exactly? Our research shows that they actively influence soil chemistry, increasing the availability of phosphate for plants, for example. Phosphate quickly binds chemically to soil particles, but worms can make it available again for plants. This is particularly useful in agricultural soil with residual phosphate from past fertilisation." A meta-analysis co-authored by Van Groenigen indicates that worms also enhance nitrogen availability in the soil. "Harvests can increase by up to a quarter when worms are involved."

Hotel CaliWormia and the joys of teaching

But how does one obtain worms for research? Van Groenigen says, "Now it gets interesting. We organise a worm-catching competition every year, and we have built a worm hotel on campus: Hotel CaliWormia." This hotel, consisting of sunken bins in the soil with optimal conditions for different worm species, serves as an experimental project to attract various worm species. Van Groenigen explains, "It is challenging and time-consuming to find different worm species for our research, so we hope they come to the hotel. It's a fun experimental project where we investigate optimal conditions for each worm species. Some prefer fresh manure, for example, while others prefer crop residues or compost." Van Groenigen enjoys this type of research as it involves learning by doing. Additionally, the worm hotel is a great attraction for a diverse audience.

He involves his students in all aspects. "You have to enjoy teaching when working at a university, in my opinion. I find it rewarding to share my knowledge and receive new insights from students. It's so rewarding when you see the 'aha' moment during a lecture, especially with those students who have to put in a lot of effort. And sometimes, truly exceptional students come by – it's a privilege to guide them!"

The role of soil in the carbon balance

As mentioned earlier, Van Groenigen considers his research in the context of climate change. He writes and is skeptical about carbon sequestration in the soil. "The production of organic carbon through photosynthesis is crucial – that's where it starts. We need it for our food, provide it to our livestock. But we must not forget to also return it to the soil. That's why I focus on how much carbon we remove from the soil and how much we need to give back." Many soils worldwide are currently losing carbon due to intensive cultivation and deforestation. "That's why I'm skeptical about the role assigned to the soil in combating climate change by storing carbon. Increasing storage is not realistic when considering how much carbon we can produce and how much we need for food. I find the IPCC estimates in this regard too optimistic. Let's first focus on limiting carbon losses from soils and on improving problematic soils."

As part of a European project, Van Groenigen is investigating the role bacteria, fungi, and worms can play in sequestering carbon in a different way. "Worms might accelerate the natural weathering of rocks, a process that also absorbs carbon dioxide from the atmosphere."

Championing pure science

Finally, he actively works against fraud in science. The news that scientists, including those from WUR, collaborated with a Saudi university partly emerged due to his whistleblowing. "That was very painful. There is, of course, too much pressure for publication and performance in science. It makes such temptations harder to resist, but it doesn't make fraud any less wrong. As a scientist, you have a special role in society. It may sound a bit old-fashioned, especially in this day and age, but you stand for objective truth-finding. That only works if our motives are not questioned. If we engage in such fraudulent practices, we lose our credibility."

The Philippe Duchaufour Medal will be awarded on April 18, 2024, in Vienna. "Looking at the list of people who have already won the medal, I feel very honoured."