Relationship between mineralisable nitrogen and microbial biomass in a range of plant litters, peats, and soils of moderate to low pH

Abstract

The mineralisation of nitrogen (N) under aerobic and anaerobic (waterlogged) conditions, and the microbial biomass carbon (C) content (using the substrate-induced respiration method) were measured in a range of plant litters, peats, and soils of moderate to low pH. The anaerobic incubation method appeared to be a more reliable indicator of the mineralisable N content of these samples than the aerobic method. The latter method sometimes gave an overall net decrease of inorganic N over the incubation period. There was a positive, highly significant, linear correlation between the microbial biomass C content and the amount of N mineralised anaerobically. The relationship between the microbial biomass C and the N mineralised by aerobic incubation was also positive, but showed greater variability. Both microbial biomass C and anaerobic N measurements were sensitive to previous changes in management from indigenous forestry to exotic forestry and grassland development. This suggests that these methods may be useful in assessing long-term fertility changes of the predominately acid forest and agricultural soils of New Zealand.

Keywords:

• soil fertility
• microbial biomass
• nitrogen
• mineralisation
• plant litter
• peats
• anaerobic incubation
• aerobic incubation
• pH