Ammonia and Nitrous Oxide Gas Loss with Subsurface Drainage and Polymer-Coated Urea Fertilizer in a Poorly-Drained Soil.

Gaseous N loss in the form of ammonia (NH₃) and nitrous oxide (N₂O) from applied urea fertilizer on poorly-drained soils can diminish agronomic production and environmental quality in the absence of best management practices such as managed subsurface tile drainage and use of controlled-release fertilizers. The objective of the study was to determine how subsurface tile drainage and applications of polymer-coated urea (PCU) affect soil N₂O emissions and N fertilizer-induced NH3 volatilization loss from a claypan soil. Drainage water management treatments consisted of conventional subsurface tile drainage, managed subsurface tile drainage, and no-drainage in combination with N fertilizer source [non-coated urea (NCU) and PCU]. Subsurface drainage treatments did not significantly (P ≤ 0.05) affect cumulative soil N₂O emissions and NH₃ volatilization loss compared to no-drainage. Averaged over 2010-2013, cumulative soil N₂O emissions from PCU and NCU were 2 and 4% of applied fertilizer N, respectively. Yield-scaled soil N₂O emissions were reduced 53% with PCU compared to NCU. The percent fertilizer loss from NH₃ volatilization was significantly (P ≤ 0.05) reduced from 2.8% with NCU to 0.8% with PCU. These results suggest that use of PCU may assist in reducing cumulative losses of N₂O and NH₃ from poorly drained claypan soils, but drainage systems operating under this study’s environmental conditions did not contribute to lowering gaseous N losses.