Nitrogen mineralization dynamics in response to organic residue and synthetic fertilizer inputs

Modern maize ( Zea mays L.) production relies on intensive fertilization with synthetic N and generates massive amounts of residue C. The short‐term effect of these inputs on N mineralization in two soils of contrasting N supply was studied by continuously monitoring CO 2 production during a 60‐day laboratory incubation experiment that also involved periodic sampling for gross N mineralization and for determination of soil microbial biomass N (MBN) and protease and deaminase enzyme activities. Residue decomposition was promoted by the addition of either KNO 3 or (NH 4 ) 2 SO 4 and was more rapid in the low‐ than high‐N‐supplying soil, whereas the opposite trend was observed for MBN and both enzyme activities. No consistent soil‐ or treatment‐specific differences occurred in measuring gross N mineralization by 15 N pool dilution. Because N is subject to microbial recycling, short‐term incubations are unlikely to be effective for studying N mineralization stimulated by organic or mineral inputs.