Nonlinear response of N2O flux to incremental fertilizer addition in a continuous maize (Zea mays L.) cropping system

• Published in: Global change biology 2005-10, Vol.11 (10), p.1712-1719
• Main Authors: McSwiney, C.P, Robertson, G.P
• Format: Article
• Language: English
• Subjects: Agricultural production; agriculture; ammonium; ammonium nitrogen; continuous cropping; Corn; Crops; denitrification; fertilizer application; fertilizer rates; Fertilizers; gas emissions; grain yield; Greenhouse gases; maize; N availability; N fertilizer; nitrate; nitrate nitrogen; Nitric oxide; nitrification; nitrogen; nitrogen fertilizers; nitrous oxide; soil bacteria; soil fertility; soil microorganisms; soil nitrogen; threshold; urea; urea ammonium nitrate; Zea mays
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/j.1365-2486.2005.01040.x

The relationship between nitrous oxide (N2O) flux and N availability in agricultural ecosystems is usually assumed to be linear, with the same proportion of nitrogen lost as N2O regardless of input level. We conducted a 3‐year, high‐resolution N fertilizer response study in southwest Michigan USA to test the hypothesis that N2O fluxes increase mainly in response to N additions that exceed crop N needs. We added urea ammonium nitrate or granular urea at nine levels (0–292 kg N ha−1) to four replicate plots of continuous maize. We measured N2O fluxes and available soil N biweekly following fertilization and grain yields at the end of the growing season. From 2001 to 2003 N2O fluxes were moderately low (ca. 20 g N2O‐N ha−1 day−1) at levels of N addition to 101 kg N ha−1, where grain yields were maximized, after which fluxes more than doubled (to >50 g N2O‐N ha−1 day−1). This threshold N2O response to N fertilization suggests that agricultural N2O fluxes could be reduced with no or little yield penalty by reducing N fertilizer inputs to levels that just satisfy crop needs.