Dr Karin Kauer1, Prof Alar Astover1
1Estonian University Of Life Sciences, Tartu, Estonia
The effect of barley and different perennial fodder crops such as grasses and clover-grass mixture on soil organic carbon (SOC) concentration and stock was studied during 1990-2014. Soil samples (depth of 0-20 cm) were collected from ongoing long-term experiment established in 1964 near Tartu, Estonia (58°22′04.09″N, 26°39′41.47″E). Treatments with perennial crop were renewed after every seven years. Every year the yield of aboveground biomass and SOC concentration after every two years were measured and SOC stock were calculated. Crop-specific C allocation coefficients (Bolinder et al. 2007) based on aboveground biomass yields were used to calculate C inputs. The precipitations and temperatures were monitored using the weather station situated next to the experiment.
During 24 year there were no remarkable changes in average year temperature but there was slight trend of decrease of average annual precipitation. At the same time average temperature from April to end of October tended to increase during study period. There was a negative relationship between temperature and precipitation. Yield of aboveground biomass, C input and SOC stock were positively related and all of them tended to increase during study period. The highest SOC stock change was in treatment with clover-grass mixture (0.43 t ha-1 year-1) and lowest in barley (0.22 t ha-1 year-1) and in grasses (0.21 t ha-1 year-1) treatments. The increase of yield of aboveground biomass and C input was highest in clover-grasses and lower in barley treatment.
The results of this experiment indicate that average annual temperature and precipitation in given region didn’t change remarkably during 24 year and didn’t describe the changes in yield of aboveground biomass and in SOC stock. The changes could be related to temperature rise during the growing season and a small reduction in precipitation is not limiting. The effect also depended on plant cover.
Karin Kauer is a researcher interested in soil organic carbon and its stock. She has been involved in various national and international projects dedicated to climate change as related to agriculture and soil organic carbon stock. Currently, she is focused on studying soil organic matter composition depending on different management practices.