Net mineralization and nitrification
Net N mineralization and net nitrification were measured immediately
after ingrowth core harvest. These were expressed as the difference in
pools of ammonium (NH4+) and nitrate
(NO3-) between an initial sample that was extracted
within 24 hours of collection and a sample that was incubated for 2
weeks at room temperature. Inorganic N was extracted from 5 g of soil
from each core in 10 mL of 1M KCl solution, and dissolved inorganic N
was determined through phenol-hypochlorite and azo-dye colorimetric
assays for NH4+ and NO3-,
respectively (Finzi et al., 1998).