Nitrous oxide and nitric oxide emissions from maize field plots as affected by N fertilizer type and application method

摘要

N2O and NO emissions from an Andisol maize field were studied. The experimental treatments were incorporation of urea into the plough layer at 250 kg N ha–1 by two applications (UI250), band application of urea at a depth of 8 cm at 75 kg N ha–1 plus incorporation of urea into the plough layer at 75 kg N ha–1 (UB150), band application of polyolefin-coated urea at a depth of 5 cm at 150 kg N ha–1 (CB150), and a control (without N application). N2O fluxes from UI250 and UB150 peaked following the incorporation of supplementary fertilizer, and declined to the background level after that, while the N2O flux from CB150 was relatively low but remained at a constant level until shortly after harvest. Accordingly, the total N2O emissions during the whole cultivation period from the three treatments were not significantly different. The fertilizer-derived N2O-N losses from UI250, UB150 and CB150 were 0.15%, 0.27% and 0.28% of the applied N, respectively. However, it was suggested that, due to the low plant N recovery, UI250 had a significantly larger potential for indirect N2O emission than the other treatments. On the other hand, NO emissions from UI250 and UB150 were 12 times higher than that from CB150, and the fertilizer-derived NO-N losses from the three treatments were 0.16%, 0.27% and 0.026% of the applied N, respectively. Significant NO fluxes were detected only when urea-N fertilizer was surface-applied and incorporated into plough-layer soil.