Greenhouse gas budgets of grassland systems

The field experiment «Kyoto-Wiese» in Oensingen (CH) shows that the conversion of arable land to intensively managed permanent grassland leads to an increase in the soil C-content of around 1.5 tons per hectare and year, provided that a sufficient amount of N-fertilizer is applied. This sequestration of carbon corresponds roughly to the yearly emission from gasoline of a passenger car. On the intensively managed field, 16 % of the saved CO2 emissions are compensated by emissions of nitrous oxide (N2O). The extensively managed field shows a similar yield as the intensive plot, but an annual release of CO2-C of around 0.5 tons per hectare with only minor N2O emissions. The reason for this difference is most likely a high rate of mineralization of soil organic matter. The extensively managed system approaches a new equilibrium with most likely a reduced soil organic matter content. Therefore, at the field scale management has a major influence on the greenhouse gas budget of grasslands.