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 5g of soil from each core in 10mL 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).