Researcher in the Spotlight – Siri Caspersen

Siri Caspersen is an associate professor in horticulture and works as a researcher within the Horticultural Production Physiology group at SLU Alnarp. Her research focuses on plant–soil interactions. How can plants efficiently use phosphorus and other nutrients from soil, fertilizers and waste products? Can we utilize mycorrhizal symbiosis in horticultural plant production? Read the interview below!

What is currently on top of your research agenda?

A project funded by Kampradstiftelsen aiming at a more sustainable use of surplus mineral nutrients from food and excreta in fish farming. The project spans from technology development for nutrient collection in aquaculture systems, to life cycle analysis for identification of main environmental challenges as well as quantification of potential climate benefits. My task is to study the release of plant-available nutrients from nutrient-loaded filter material and to evaluate the performance of the material as a substrate component and mineral nutrient source for plant cultivation.

Tell us about your latest publication.

My latest publication Nutrient challenges with solid-phase anaerobic digestate as a peat substitute – Storage decreased ammonium toxicity but increased phosphorus availability, published in Waste Management, concerns some of the challenges related to the use of the solid digestate fraction from biogas plants as a fertilizer and peat substituent. Firstly, a high pH combined with high ammonium contents in the fresh digestate can lead to large losses of N as ammonia emission as well as to phytotoxicity. Secondly, depending on the feedstock used, high total and available contents of phosphorus can be a challenge, increasing the risk of losses of P to the environment. Hence, the availability and losses of N and P from digestates needs to be closely controlled to optimize both nutrient use efficiency and plant performance. 

What led you to your particular field of research?

I have a background in biology with a specialisation in plant physiology. My main research interests lie within the area of plant–soil interactions. After my PhD on allelopathy and root exudates in hydroponics, I have mainly been working within the areas of plant nutrition and mycorrhizal symbiosis, as well as the utilisation of organic nutrient sources in horticultural cultivation systems.

What are the implications of your research for society?

Today, there is a demand for improved utilisation of phosphorus in agricultural and horticultural production systems, both because phosphate rock is a limited resource and the accumulation of fertiliser P in soils increases the risk of losses, leading to eutrophication. Improving P use efficiency, as well as utilising P in waste products such as digestates and struvites, can contribute to a circular economy and increase sustainability.

Finally, let´s say you have unlimited research funds; where would your research be five years from now?

Mycorrhizal symbiosis could potentially reduce the need for easily available phosphorus fertilisers. With unlimited research funds, I would be searching for plant traits and genes important for the establishment of efficient mycorrhizal symbioses, with the aim of increasing phosphorus efficiency in horticultural cropping systems.

Thank you for a very interesting interview, Siri! We wish you the best of luck and success in your future path!

(Photo: Knut-Håkan Jeppsson)