Characterization of nitric oxide emissions from an intensively managed agricultural soil in North Carolina, USA

Nitric oxide (NO) plays an important role in tropospheric photochemistry. Biogenic soil emissions of Nitric Oxide were measured from an intensively managed agricultural row crop (corn, Zea mays) during a four-week period (May 15 through June 9, 1995). The site was located in Washington County, near the town of Plymouth, which is in the Lower Coastal Plain of North Carolina, U.S.A. Soil NO flux was determined using a dynamic flow-through chamber technique. The measurement period was characterized by two distinguishing features: an application of nitrogen (N) fertilizer at the midpoint of the experiment and a non-typical rainfall pattern. Average NO flux prior to the application of N fertilizer was 31.5 +/- 10.1 ng N m(-2)s(-1), and more than doubled (77.7 +/- 63.7 ng N m(-2)s(-1)) after the application of a side dressing of N fertilizer. Average soil extractable nitrogen values did not change significantly following application of the side dressing of N fertilizer. We attribute this failure to detect a significant difference in soil extractable nitrogen following N fertilization to the method in which the fertilizer was applied, the subsequent rainfall pattern, and the mechanics of our sample system. NO flux followed the same diurnal trend as soil temperature, with maximum NO emissions coinciding with minimum soil temperature. NO flux was found to increase exponentially with soil temperature, but only after fertilization. Due to sub-surface irrigation practices employed by the farmer, changes in soil water content were minimal and no relation could be drawn between soil water content and NO flux.