Short-Term Soil Nitrous Oxide Emissions as Affected by Enhanced Efficiency Nitrogen Fertilizers and Temporarily Waterlogged Conditions

Abstract

Poorly-drained claypan soils in the Midwestern United States experience periods of short-term soil saturation shortly after pre-plant N fertilization, which may result in relatively large amounts of soil surface N₂O emissions. Slowing the release or conversion of N fertilizer to soil NO₃ early in the growing seasonthrough the use of enhanced efficiency fertilizers (EEF) could be an effective strategy for reducing soil N₂O emissions and gaseous N loss during a period of relatively low plant N demand. The objective of this study was to determine the effects of short-term soil waterlogging and pre-plant applications of conventional and EEF on soil inorganic N and N₂O emissions during and up to four days following a waterlogging event during the dry down period. A two-year field study planted to corn (Zea mays L.) was initiated in 2012 on a poorly-drained claypan soil in Northeast Missouri. Waterlogging treatments were initiated at the V6 corn stage of phenological development. Main plots consisted of no waterlogging or water ponded 7 to 13 cm above the soil surface for three days, and sub-plot N fertilizer treatments [non-treated control (CO), or preplant broadcast applications of 168 kg N ha^-1 of urea (NCU), urea plus nitrapyrin nitrification inhibitor (NCU+NI), and polymer coated urea (PCU)]. In 2012, greater cumulative soil N₂O-N emissions of 2.8 kg N₂O-N ha^-1 were observed with PCU in comparison to NCU over the entire seven day sampling period. A significant portion of cumulative soil N₂O emissions were associated with the four day soil drying phase in 2012, where PCU and NCU+NI had greater emissions (1.9 and 1.2 kg N₂O-N ha^-1) compared to NCU. The proportion of N fertilizer lost as N₂O-N averaged over all pre-plant N treatments during the 2012 and 2013 sampling periods in the non-waterlogged soils were 0.04% and 0.03%, and 1.1% and 2.6% in the waterlogged soils, respectively. These results suggest that a large proportion of the cumulative soil surface N₂O emissions typically observed in these poorly-drained soils over a growing season may occur during and shortly after soil waterlogging events.