The mitigation of greenhouse gas emissions from agriculture is one step in Finland's way towards carbon neutrality. In agriculture, emissions are released by animals and soil. Researchers and decision-makers are particularly interested in peat soils.
In Finland, peat soils account for only ten per cent of agricultural land; yet they are responsible for more than half of the country’s agricultural emissions. At the moment, researchers are working hard to find smart agricultural techniques for climate and food production, so that peat soils could continue to be used in food production. The proportion of peat soils used as agricultural land varies from one region to the next. In some places, they are important areas of food production.
“Agricultural practices are one factor in the equation that can influence greenhouse gas emissions,” Researcher Saara Lind from the Natural Resources Institute Finland says.
“Peat soils have a lot of organic material left in them. When the soil is drained, peat decomposes at an accelerated rate, which causes greenhouse gas emissions, such as carbon dioxide and nitrous oxide, into the atmosphere. We are trying to find a balance between growing food and still mitigating emissions by managing the water table level.”
Raising the water table level on the scale of a field is challenging.
Saara Lind
Researcher, Natural Resources Institute Finland
Farmers need accurate information on optimal water table levels. For this purpose, an experimental site has been set up in a peat soil in northern Savo. The Maaninka Särkisuo site is one the new research areas of the Natural Resources Institute Finland, and it is used as an experimental setting in the ORMINURMI project.
“This field is used for the cultivation of forage. This year, the field was established in a cover crop of oats and wheat, and we are growing a grass mixture of timothy and meadow fescue. There is also a strong natural seed bank in the field, so we can see also other species here. The field is drained peatland, and we are now using subsurface drains to manage the water table level,” Lind explains.
The Natural Resources Institute Finland is responsible for the cultivation of the field, and the University of Eastern Finland is involved in the measurement of greenhouse gases, among other things. The study also examines biomass, the development of root systems, and forage yields.
Doctoral Researcher Zheng Yu from the Department of Environmental and Biological Sciences at the University of Eastern Finland is carrying out measurements for his PhD thesis at the Särkisuo site, under a grant awarded by Nessling Foundation. Greenhouse gas emissions are measured both on site in the field, in response to water table fluctuations under natural conditions, and in mesocosm experiments controlling the water table, where greenhouse gas emissions are measured by studying soil samples.
“The aim is to combine data from all the measurements and conclude the optimal water table levels in relation to both greenhouse gas emissions and yields,” Zheng Yu explains.
"High water table levels are the best way to slow down the decomposition of peat, thereby reducing carbon dioxide and nitrous oxide emissions."
However, it may cause methane emissions.
Zheng Yu
Doctoral Researcher, University of Eastern Finland
“In my doctoral research, I will also examine the effects of different water table levels on nitrous acid and nitric oxide emissions, which also have a significant impact on the climate and air quality,” he says.
Zheng Yu's field experiment involves, firstly, a metal chamber, a box without a bottom, which is placed on the field. During one measurement session, four different gas samples are taken from inside the chamber. The samples’ gas concentrations, including methane, nitrous oxide and soil and plant respiratory carbon dioxide, are then analysed in the laboratory using a gas chromatograph.
The other in-situ measurement monitors the exchange of carbon dioxide. The chamber is transparent, and the plants get a normal amount of light, which means that carbon dioxide levels inside the chamber decrease due to photosynthesis. This will be followed by a measurement under dark conditions, where photosynthesis is prevented. The carbon dioxide concentration is determined every other second for a duration of two minutes.
“The plants may not sequestrate carbon dioxide today, because clouds are casting a shadow, and that has an impact on how much effective light they get,” the researchers say.
“The results indicate the net exchange of carbon dioxide. Modelling is used to determine carbon dioxide sequestration rates under different light conditions.”
Greenhouse gases are also measured in the field using an automatic, continuous eddy covariance technique. This experiment determines the concentrations of greenhouse gases carried by the wind, as well as wind direction and wind speed. These give information about the direction and the speed at which gases are moving. Based on this data, it is possible to calculate greenhouse gas fluxes.
Greenhouse gas flux measurements require very accurate and quick devices because measurements are performed at the 10Hz frequency, i.e., ten times per second. The measurement tower has an anemometer for determining wind speed and direction, as well as a separate analyser for the measurement of carbon dioxide concentrations.
“A separate device for determining the concentrations of nitrous gas and methane will be located in a booth near the tower. This device will be introduced already this autumn,” the researchers say.
“In addition, the measurement tower has a meteorological station. This data is used for modelling of the measured greenhouse gas exchange results and for explaining their underlying causes. Because measurements are performed on a continuous basis, it is important to monitor their success. The measurement tower’s function and data collection can be monitored in real time using a mobile app.”
“This enables rapid intervention in the event of a problem with the measurements.”
“Research into the carbon dioxide emissions released by peat soils is a broad entity, and our understanding of it is still incomplete. The development of measurement methods and modelling constantly gives us new insight into how peat soils can be used. There is still hope of a better future for the climate, but action is needed now."
"It’s not too late yet,” the researchers say, reassuringly.
Funded by the Ministry of Agriculture and Forestry, the ORMINURMI project by the Natural Resources Institute Finland and the University of Eastern Finland generates new knowledge on the greenhouse gas exchange of agricultural lands as part of Finland's aim to become carbon neutral by 2035. The project explores various agricultural practices and aims to explore the potential of mineral soils in increasing carbon sequestration. With regard to peat soils, possibilities for reducing the release of carbon is explored. The aim is to produce optimal overall solutions that take into account production, economy and environmental efficiency.
