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 CO₂ 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 KNO₃ or (NH₄)₂SO₄ 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 ¹⁵N 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.