Slurry and urea applications are part of normal nutrient management on grassland farms utilizing grazed grass and silage for animal production. It was hypothesized that management history would result in a different carbon response to slurry and urea applications for the same soil type because of differences in soil micro-environment, including microbial biomass and activity, are formed and regulated by long-term management history. An Irish grassland soil of the Skeagh Series was sampled in three fields, each with a long, consistent management history: Soil A was associated with extensive grazing by horses; soil B with medium intensity grazing by sheep and cattle, and grass silage conservation; and soil C with intensive dairy cow grazing. There were three slurry treatments (S₁, the control of no slurry; S₂, slurry mixed with soil; S₃, slurry added on the soil surface) and three urea treatments (N₁, the control of no urea; N_2, all urea applied at one time; and N₃, three application, 30 days apart, totaling the same amount of urea as N₂) designed to supply 36 g C m^﹣2 and 2 g N m^﹣2 during an 85 day incubation trial. Soil pH, total carbon, cold water extractable organic carbon, soil respiration and two C-related enzymes (β-glucosidase and CM-cellulase) were measured. All measured soil properties showed a significant difference (P < 0.05) by management history, indicating a strong influence of long-term management on response. β-glucosidase and CM-cellulase activity showed a strong relationship with soil management history rather than with slurry or urea additions. It was concluded that management history was important to C dynamics. Slurry mixed with soil resulted in a greater soil carbon loss than slurry applied on the soil surface. One large dose of urea caused greater soil carbon loss than multiple small doses.