Coupling of N₂O and CO₂ fluxes from agriculture in Michigan

CO₂ has been known to cause global warming, and N₂O is the largest contributor to the greenhouse gas burden of cropping systems in the United States due to application of fertilizer. In our study, fluxes of N₂O and CO₂ were measured at two maize fields and one reference grassland from Kellogg Biological Station in Southwest Michigan. Here we compared two measuring systems, traditional GC method and LGR/Li-Corsystem. Our initial results show that the two measuring systems are consistent (N₂O slope=0.96, R2=0.96; and CO₂ slope= 1.03, R2=0.86 measuring from the same chamber). Measurements done in pairs of chambers suggest great spatial variations, despite that the chambers were only0.5 meter apart. The two systems are still comparable by averaging 8pairs of chambers distributed within one site. Increase of CO₂ fluxes were observed the second day after fertilization, but no significant change of N2O fluxes was shown. After artificial rainfall, boosting N₂O fluxes and further increase in CO₂ fluxes were demonstrated. Our result indicates that precipitation is necessary before a prominent N₂O peak. In our LGR/Li-Cor system, CO was also measured from chambers. Interesting CO fluxes were shown in our experiment. Soil, which is usually considered as a CO sink, emits CO in some chambers during our measurement, which is probably related to the nationwide forest firesand lack of precipitation during the period.