Nitrogen (N) is essential major nutrient for the growing of plants but at the same time a source of harmful greenhouse gas, nitrous oxide (N2O) and a source of eutrophic and/or unhealthy load, nitrate (NO3-), for surface and ground waters. Despite the preventive measures, for example in Finland 53% of the annual N load to watercourses as well as over 50% of our annual N2O emissions originates from agriculture. One option to mitigate these universal problems is the addition of biochar on soil. It has been noticed that the effects of biochar on crop growth, greenhouse gas fluxes, nutrient retention and so on varies greatly depending on the soil type, plant species, biochar type, conditions in soil and age and amount of the added biochar. So far there is not yet clear overall picture what kind of biochar should be used in certain soils for certain purposes (for example to maximize crop growth or to minimize greenhouse gas emissions or to minimize nutrient leaching). This study focuses on the effects of biochar on N cycling in agricultural soils and thus contributes to the resolving of the environmental problems (greenhouse gas emissions, nutrient leaching) caused by agriculture. The study is extremely timely and it also produces information needed to the adaptation of food production for climate change. The study follows the most recent developments in biochar and agricultural studies. MTT role in this study is to organize a field experiment where effect of biochar on N2 fixation and N2O emissions from a red clover - grass mixtures are measured. Special focus will be put on winter time emission that are presumably high especially from clover rich canopies.