SOIL EMISSIONS OF NITRIC-OXIDE AND NITROUS-OXIDE FROM NO-TILL CORN

Fertilized agricultural soils can be a significant source of emissions of NO and N2O into the atmosphere. This study was conducted to determ ine the influence of N rate on the emissions of these gases in a no-ti ll corn (Zea mays L.) crop grown in western Tennessee. The influence o f N rate was assessed for a 210-d period on replicated plots receiving 0, 140, and 252 kg N ha(-1) (0N, 140N, and 252N) as ammonium nitrate (AN). Plots were located on a Routon silt loam (fine-silty, mixed, the rmic Typic Ochraqualf) at the West Tennessee Agricultural Experiment S tation in Jackson, TN. Gas fluxes were measured by static chamber boxe s located on plots. The measurement technique was automated and replic ate chamber estimates were made eight times daily for the entire study period. Fertilizer application significantly affected both NO and N2O emission rates. The cumulative N2O-N lost from the fertilizer treatme nts was from 10 to 20-fold that of NO. On an areal basis, the 140N tre atment emitted 4.23 kg N2O-N and 0.19 kg ha(-1) of NO-N whereas the 25 2N treatment emitted 6.56 kg N2O-N and 0.50 kg ha(-1) NO-N. Soil param eters of water-filled pore space (WFPS), NO3- and NH4+, were correlate d with N2O emissions but only soil NO3- was correlated with NO flux. O ur data, and more recent data in the literature, suggest that N2O emis sions from fertilized soil may be considerably higher than previously thought. Emissions of N2O were 2.6 to 3.0% of the fertilizer amounts a pplied. These higher emissions may, in part, explain some of the reaso n for the shortfall in the global N2O budget.