Nitrous Oxide Emissions In Claypan Soils Due to N Fertilizer Source and Tillage/Fertilizer Placement.

Nitrogen fertilization for agricultural production is a major contributor to increased soil nitrous oxide emissions.  These emissions may contribute to global warming and ozone depletion. Nitrogen fertilizer source and placement can influence soil nitrous oxide (N₂O) emissions by affecting the concentration of ammonium and nitrate available for nitrification and denitrification throughout the growing season. The objectives of this research were to quantify the effect of fertilizer placement (no-till, surface broadcast and strip-till placed at 20 cm) and N fertilizer source (non-coated urea, polymer-coated urea, non-treated control) on soil N₂O emissions from agricultural practices in claypan soils located in Northeastern Missouri. Soil N₂O emissions were measured and analyzed using static chambers and gas chromatography, following the USDA protocol (GRACEnet) for field measurements of trace gases. The field experiment planted to corn (Zea mays L.) was initiated in 2009 and included six treatments with three replications and two subsamples in a randomized complete block design. No-till, broadcast, and polymer-coated urea management system had the highest average cumulative soil N₂O emissions after fertilization (7.8 kg-N₂O ha^-1), which represented 3.54% N lost from fertilizer as N₂O in 2009.  No significant interaction was found between fertilizer source and placement (P < 0.05). Strip-till management emitted 0.006 kg N₂O-N per bushel of corn grain produced, which was significantly lower than no-till management that emitted .011 kg N₂O-N Bu^-1 (P < 0.10). Additional results from the 2010 season will be presented.