Effect of Temperature and Water on Gaseous Emissions from Soils Treated with Animal Slurry

Microbial respiration and denitrification are greatly affected by abiotic factors, but they are difficult to assess in natural environments. Under controlled conditions the interactions between temperature and soil water content on microbial respiration, N2O production, and denitrification in soil amended with animal slurries were studied. The effects of the abiotic factors on the biological processes were monitored for 8 wk in repacked soil cores amended with pig or cattle slurry. The soil cores were incubated at 43, 57, and 72% water‐filled pore space (WFPS) and at 10, 15, and 20°C with or without addition of 10% acetylene. The amount of N2O lost at 72% WFPS corresponded to 8 to 22% of the slurry's NH+4 content, but to only 0.01 to 0.9% at 43 to 57% WFPS. Denitrification losses at 72% WFPS accounted for 17 to 58% of the slurry's NH+4 content, but for only 0.01 to 1.2% at 43 to 57% WFPS. The amount of available C accounted for by denitrification was 8 to 16% of total respiration at 72% WFPS, but only 0.03 to 0.4% at 43 to 57% WFPS. Both N2O production and denitrification peaked earlier in the cattle‐slurry treated soil than in the pig‐slurry treated soil, whereas the total N loss was greatest from the latter. Neither amendments nor soil water contents seemed to affect the Q10‐values for the CO2 production, resulting in values between 1.6 and 2.6. At 72% WFPS, N2O production and denitrification had Q10‐values ranging between 3.3 and 5.4. High temperatures enhanced both aerobic respiration and denitrification, and aerobic respiration further enhanced denitrification by consuming oxygen, resulting in strong sensitivity of denitrification to temperature.