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 determine the influence of N rate on the emissions of these gases in a no-till corn (Zea mays L.) crop grown in western Tennessee. The influence of 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, thermic Typic Ochraqualf) at the West Tennessee Agricultural Experiment Station in Jackson, TN. Gas fluxes were measured by static chamber boxes located on plots. The measurement technique was automated and replicate 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 treatments was from 10 to 20-fold that of NO. On an areal basis, the 140N treatment emitted 4.23 kg N2O-N and 0.19 kg ha(-1) of NO-N whereas the 252N treatment emitted 6.56 kg N2O-N and 0.50 kg ha(-1) NO-N. Soil parameters of water-filled pore space (WFPS), NO3- and NH4+, were correlated with N2O emissions but only soil NO3- was correlated with NO flux. Our data, and more recent data in the literature, suggest that N2O emissions from fertilized soil may be considerably higher than previously thought. Emissions of N2O were 2.6 to 3.0% of the fertilizer amounts applied. These higher emissions may, in part, explain some of the reason for the shortfall in the global N2O budget.