Quantification of priming and CO2 respiration sources following slurry-C incorporation into two grassland soils with different C content.

content. Slurry incorporation into the soil strongly increased soil CO2 respiration compared with the unamended soil. Total (40 day) cumulative CO2 flux was higher for the Pelostagnogley than the Brown Earth. The 13 C natural abundance tracer technique enabled quantification of the sources of respired CO2 and priming effects (days 0‐9). Proportionally more slurry-derived C was respired from the Pelostagnogley (46%) than the Brown Earth (36%). The incorporated slurry-C was lost twice as fast as the native soil C in both soils. Slurry incorporation induced a priming effect, i.e. additional release of soil-derived C, most pronounced in the Pelostagnogley (highest C content). The majority of respired soil-derived C (>70%) was primed C. The study indicated that potential reductions in ammonia volatilisation following slurry injection to grasslands might be negated by enhanced loss of primed soil C (i.e. pollution swapping). Copyright # 2003 John Wiley & Sons, Ltd. Intensive application of animal slurries to grassland results in increased greenhouse gas emissions, ammonia volatilisation, and nitrate and phosphorus leaching into surface and groundwater. 1,2 However, slurry injection into the soil can reduce ammonia volatilisation by up to 50%. This altered way of slurry application to agricultural land can potentially also influence soil CO2 respiration. Unfortunately, less information is available concerning sequestration and losses of C from slurries applied to agricultural soils. 3–5 Moreover, none