Microbial nitrification, denitrification and respiration in the leached cinnamon soil of the upper basin of Miyun Reservoir

Leached cinnamon soil is the main agricultural soil distributed in the North China Plain. In this research, leached cinnamon soil samples were collected in the upper basin of Miyun Reservoir (northeast of Beijing, China). The BaPS method (Barometric Process Separation) was applied to measure nitrification, denitrification and respiration rates. The rates of nitrification, denitrification and respiration were 0–120.35 μg N/kg SDW h, 0–246.86 μg N/kg SDW h and 0.17–225.85 μg C/kg SDW h (Soil Dry Weight, SDW), respectively. The emission rates of CO2 and NxOy through nitrification, denitrification and respiration were 1.00–547.80 and 6.00–4850.65 μmol/h, respectively. The analysis of relationships between nitrification, denitrification and respiration rates indicated that these three microbial processes were interacted, which posed impacts on soil nitrogen availability. As indicated by the results, C:N ratio coupled with [inline-graphic not available: see fulltext] content could be taken as the indicators of [inline-graphic not available: see fulltext] content, which is usually the predominant form of N available to plants growing in soil. Results showed that [inline-graphic not available: see fulltext] content was the highest (i.e., >62.4 mg/kg) when C:N ratio was 5.30–8.40, meanwhile [inline-graphic not available: see fulltext] content was 3.71–4.39 mg/kg. Nevertheless, [inline-graphic not available: see fulltext] content was the lowest (i.e., <6.40 mg/kg) when C:N ratio was 9.2–12.10, meanwhile [inline-graphic not available: see fulltext] content was 3.41–4.35 mg/kg.