Our greenhouse experiment on lake sediment phosphorus recycling up and running!

Past months we have been busy with collecting, drying and recycling muddy sediments from lakes in Estonia and Finland- and now the sediments are applied to pots in greenhouse and ryegrass thriving in them.

 

The experiment is a part of the project searching ways of sustainable lake restoration by sediment removal and subsequent sediment phosphorus (P) reuse in agriculture. As we know, large amounts of P are concentrated in lake sediments, and water quality problems (eutrophication) are often related to the release of this P. At the same, the scarcity of mineral P resources is challenging future society. Hence we focus holistically on both lake ecosystem functioning and agroecological sustainability.

Such a practice appeared to be successful in our pilot study area Lake Mustijärv (in central Estonia). In the lake, changes in P release from sediments were related to the variations in iron-bound P (Kiani et al., 2020). At the same time, this fraction was the major source of P for the grass uptake in the experimental study on the sediment P reuse (Kiani et al., 2021). Our recent studies of the four eutrophic lakes in southern Finland (Päijät-Häme region) revealed similarity of the mechanisms behind sediment P release, indicating a high potential for the sustainable model of lake restoration by sediment removal and reuse in agriculture in these lakes. However, the bioavailability of the sediment P is likely low, as soils (and sediments) in Finland are saturated with iron.

In our latest experiment, we explore whether biochar, lime and arbuscular mycorriza can improve the availability of sediment P for crops (ryegrass). We test the fertilizing ability of sediments from the four lakes of the Päijät-Häme region (Enonselkä basin of Lake Vesijärvi, Matjärvi, Kutajärvi, Kymijärvi), but also from two Estonian lakes having different geology. The results will be extrapolated for larger areas, based on the sediment properties from a variety of lakes in southern Finland analysed within the project.

The project is led by Dr Olga Tammeorg (Ecosystems and Environment Research Programme, University of Helsinki) in synergy with our AgriChar Research group. We acknowledge particularly Päijät-Häme Regional Fund of Finnish Cultural Foundation and Niemi Foundation for providing funding and our Dream Team of hard-working assistants from France: Lena, Jeanne, Diane, Kevin for all their help. Finally, we highly appreciate the support of Vesijärvi Foundation and City of Lahti and University of Tartu, especially Dr Tanel Vahter for collaboration.

 

We wish everyone Merry Christmas and a Happy New Year 2022!