Tillage and nitrogen application effects on nitrous and nitric oxide emissions from irrigated corn fields

A 2-year study was conducted to investigate the potential of no-till cropping systems to reduce N2O and NO emissions under different N application rates in an irrigated corn field in northeastern Colorado. Flux measurements were begun in the spring of 2003, using vented ( N2O) and dynamic ( NO) chambers, one to three times per week, year round, within plots that were cropped continuously to corn ( Zea mays L.) under conventional-till ( CT) and no-till ( NT). Plots were fertilized at planting in late April with rates of 0, 134 and 224 kg N ha(-1) and corn was harvested in late October or early November each year. N2O and NO fluxes increased linearly with N application rate in both years. Compared with CT, NT did not significantly affect the emission of N2O but resulted in much lower emission of NO. In 2003 and 2004 corn growing seasons, the increase in N2O-N emitted per kg ha(-1) of fertilizer N added was 14.5 and 4.1 g ha(-1) for CT, and 11.2 and 5.5 g ha(-1) for NT, respectively. However, the increase in NO-N emitted per kg ha(-1) of fertilizer N added was only 3.6 and 7.4 g ha(-1) for CT and 1.6 and 2.0 g ha(-1) for NT in 2003 and 2004, respectively. In the fallow season ( November 2003 to April 2004), much greater N2O ( 2.0 - 3.1 times) and NO ( 13.1 - 16.8 times) were emitted from CT than from NT although previous N application did not show obvious carry-over effect on both gas emissions. Results from this study reveal that NT has potential to reduce NO emission without an obvious change in N2O emission under continuous irrigated corn cropping compared to CT.