Offsetting N2O emissions through nitrifying CO2 fixation in grassland soil

This paper presents data on the net greenhouse gas balance (measured as CO2 equivalents) of N2O emitted and C fixed in nitrifying pastoral soils over a 10-week laboratory incubation period. In a low nitrogen environment without urine deposition, typical of large areas of grassland, archaeal-dominated nitrification increased soil organic carbon (SOC) to the point that these offset N2O emissions. In a very high N environment typical of urine patch, where bacteria dominated nitrification, N2O emissions were offset by C fixation for 3 weeks but were then overwhelmed by a rapid increase in N2O production. Given the very large area of grasslands globally and the importance of nitrification in grassland soils, our finding provides a basis for re-evaluating the budget for net greenhouse emissions from grassland.