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The aim of the CARBO study is to reduce the environmental impact of the Finnish milk and meat chain through research-based information, new innovations and farm pilots while improving the profitability and export competitiveness of Finnish agriculture. Primary food production needs to be more transparent and sustainable.

The biogeochemistry research group from the 91���� has been working on carbon balance measurements, which have now been underway for more than a year in a test field in Maaninka in cooperation with the Natural Resources Institute Finland. Researchers from the institute take care of the maintenance, mowing and fertilising of the test plots, while the university’s researchers are responsible for collecting gas samples, analysing them and calculating the results.

“We have been regularly measuring the greenhouse gas balances for carbon dioxide, nitrous oxide, or laughing gas, and methane using the chamber method.  Measurements have been taken weekly from all 25 test plots of CARBO grass during the growing season, and slightly less frequently in winter, two or three times a month”, says Professor Marja Maljanen.

“Methane and nitrous oxide fluxes are calculated from changes in the concentration of gas samples taken from the chambers at certain intervals. The gas samples are collected from the chambers in the field, and they are analysed using gas chromatography at the Department of Environmental and Biological Sciences in Kuopio”, Maljanen describes.

“In the nitrogen fertilisation experiment, the test plots were treated with 0, 150 and 300 kilograms of nitrogen per hectare, five in parallel of each. The cutting height test compared grass mowed to a height of six centimetres and grass mowed to a height of 12 centimetres, also in five parallel plots.”

The carbon dioxide exchange between the grass and the atmosphere is measured using the chamber method and an analyser in the field, allowing the current situation to be seen immediately. However, to determine the carbon balance for the day, growing season or year, it is necessary to model the carbon balance for the missing time points using, among other things, continuous temperature, humidity and photosynthetically active radiation (PAR) data.

“Due to the hassle in the spring with the coronavirus and other things keeping us busy, the greenhouse gas or carbon balance calculations for the full year have not yet been completed. However, based on the preliminary results, it can be said that the grassland studied has the potential to sequester carbon. The final results regarding the impact of the treatments on carbon sequestration in relation to yield level have not yet been calculated.”

Nevertheless, the ambitious goal of carbon-neutral milk production seems to still be a long way off at this stage, but the minimisation of greenhouse gas emissions is ongoing.

“The assessment of greenhouse gas emissions from milk production will include a life cycle survey, and the carbon balance of grass is only a small part of it”, Maljanen says.

The researchers intended to measure gas fluxes using the so-called snow gradient method last winter, but in the absence of snow, they had to use chambers, which is considerably more laborious in winter than it is in summer.

“In the chamber systems, water is used to seal the chamber to be gas-tight. This is done with a ‘collar’ installed in the ground. The water freezes in the cold, of course, so the frozen water must first be chipped out of the grooves of the collars, with warm water poured in its place. Fortunately we did not have many degrees of frost”, Maljanen thinks back.

“The dry summer of 2019 also affected the results. Especially the emissions of nitrous oxide were significantly lower than normal, or the corresponding emissions previously measured from the same field. As a greenhouse gas, nitrous oxide is about 300 times stronger than carbon dioxide.”

“It is difficult to estimate how the dryness affected the carbon balance, but it is precisely because of these varying conditions that two years is a really short examination period”, Maljanen says.

“The measurements will be continued until the end of the growing season, with the results calculated thereafter. We believe that we have a good chance of receiving further funding for the project to cover the entire grass crop rotation.”

“To date, our study has involved postdoctoral researchers, interns and those writing their doctoral dissertations working remotely, in the field and in the laboratory. I myself am working more in the laboratory than in the field this summer, even though I would gladly participate more in the field work as well”, she says.