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!

New recycling fertilizer experiments & growing season 2021 sample analyses ongoing

 We are happy to announce that our new recycling fertilizer experiments focusing on granular fertilisers based on oil-shale ash and lime enriched with essential soil nutrients is past the laboratory testing phase. In this project we work in synergy with Estonian NGO Soil Innovation Cluster and Estonian University of Life Sciences, University of Tartu  and Ekosovellus and the aim of our work package is to test most suitable fertilizer recipes for their liming and fertilisation efficiency first in lab tests and then in lab incubation. 

Lab and greenhouse tests of new granular organic fertilisers in Helsinki.

 

The recipes include mainly oil shale ash, dolomite, limestone, meat bone meal and vinasses in different proportions and currently we are finalizing report on the lab tests. Some of the fertilisers were comparable to limestone in regards of liming efficacy and also were quite promising with their fertilising properties. Now in winter we are continuing with the next step, greenhouse experiment with most promising fertilisers with barley as the crop. Next summer 2022 we will continue to field experiments, stay tuned for the results and check also other interesting results from the Cluster website https://soilprotection.earth!

Naturally, our field experiments have all been also harvested by now and plant and soil samples being currently analysed in labs. The grass yield of long-term biochar experiments was harvested in September, and under the professional coordination of Mari Unnbom, also the yields of HYKERRYS recycling fertiliser experiment were harvested, even the faba beans where we had most challenges this year. The active experimentation and monitoring in HYKERRYS experiments ends this autumn, closing five-year crop rotation 2016-2021 and thus MSc students Heikki Sikanen and Nea Similä study carefully also the longer-term effects on soil aggregate stability and water retention capacity composts and other fertilisers had. 

Harvesting, sampling and analyses of nutrient uptake and soil aggregate stability from our field experiments 2021.

Further, this autumn our research group is strengthened with four amazing trainees from UniLaSalle, France: Kevin Van Assche, Diane Maujoin,  Jeanne Bideault and Lena Jacquot. They have been busy with field sampling, yield analyses as well as what you see in the photo, analyses of nutrient uptake of plants from different fertilisers. A dream team indeed!