Harnessing the Rhizosphere to Protect Our Soil

The soil under our feet is crucial for human prosperity. It filters water as well as pollutants, acts as a carbon sink, and, as Tanja Mimmo, the Director of the Competence Centre for Plant Health at the Free University of Bozen-Bolzano (unibz) points out: “98% of worldwide food comes from soil.” But this soil is under threat, with a crisis dubbed ‘phosphogeddon’ looming over our food security. Phosphorus is an essential nutrient for plant health, and it’s one that is widely fed to plant crops in fertiliser. The world is facing a troubling shortage of phosphorus, and its overuse in fertiliser has far-reaching environmental impacts. We need to find a better way of getting plants the nutrients they need - and the answer may lie in the rhizosphere, the area of soil around a plant root where, according to Tanja, “all the important reactions are taking place and why and how the plant is getting water and nutrients”. With more than 20 years of research experience, this is her primary area of focus. 

The rhizosphere is where plant roots release exudates, “a very complex cocktail of both organic and inorganic compounds”, which help the plant to increase the uptake of vital nutrients like phosphorus. Tanja tracks and samples the rhizosphere of plants using different root box systems called rhizoboxes, to determine which compounds are being released in which conditions. These findings could be used to develop agricultural methods whereby plants can better adapt to their conditions more effectively, potentially reducing or eliminating the need for fertilizers. We could focus on breeding varieties of plants that have an improved capacity for mineral uptake, she says, or use intercropping, where a plant with reduced exudation ability is grown next to plants that are good at releasing exudates. “Plant age, the variety and/or species, soil characteristics, they all influence this exudation process. So it's really complex here, there's a lot of basic research needed behind it to then apply it in the field and to have the best results.”

Based in South Tyrol, the Italian alpine region bordering Austria and Switzerland, unibz couldn’t be better situated for the study of soil. The area is agriculture-oriented, with the most important produce coming from apple orchards and vineyards, which thrive in the mountainous region. This means the policymakers and agricultural workers there have a vested interest in addressing agronomic practices “to increase and maintain soil health” explains Tanja. That’s also why her department is coordinating one big European Union projects ECHO (Engaging Citizens in Soil Science: The Road to Healthier Soils) and is partner of HuMUS (Healthy Municipal Soils) are designed to engage citizens and regions respectively in the pursuit of healthy soil. As the director of the centre, Tanja leads a team that is in her words “quite diverse in research topics”. Alongside the rhizosphere, they investigate heavy metal and microplastic contamination in soil, how to enhance agronomic practices to increase carbon sequestration, and also how certain techniques can enhance soil biodiversity. All of these areas can affect crop yields, which are responsible for a large majority of the food we buy in our supermarkets. “So it's actually really important to understand what is happening below our feet,” she states.

Born and raised in Bozen-Bolzano, Tanja spent 13 years studying and working at the Universities of Bologna and Torino, where she completed her PhD and postdoc. She highlights a key difference between how her research was received by the local producers in Bologna compared to Bozen-Bolzano. “It was really difficult to get in touch with the farmers” in Bologna, she says. “They didn't want to listen to you because ‘you're a researcher, doing only basic research, you're not finding any solution for us’.” In South Tyrol she has found a “completely different situation”, where researchers work closely with local farmers who are interested in understanding their research and finding out how it can be applied to help their crops. This mutually beneficial exchange means the researchers feel their work is making a positive impact in the real world.

The valley is not just agriculturally unique, but linguistically too. unibz has three official languages, with teaching in English, Italian, and German. The university prides itself on its international community of staff and students, who make speaking foreign languages an everyday reality on campus. While this creates a cultural diversity within research teams, they are further diversified by the interdisciplinary approach to research. Tanja calls this a “win-win situation where you really can bring forward new ideas and new results”. Ultimately, she chose unibz because for her it’s a great place to keep doing her research into multiple areas. “One minute I need to talk about biodiversity in the soil, and then the other minute I need to talk about plant physiology. So it's really challenging, but that's also makes it really interesting,” she concludes.