Urea Fertlizier Placement on Greenhouse Gas Flux and Plant Growth.

Abstract

Urea Fertilizer Placement Effects on Soil Greenhouse Gas Flux and Plant Growth

F.E. Johnson*, P.P. Motavalli, K.A. Nelson, and R.J. Kremer

Nitrogen (N) fertilization of poorly drained agricultural soils may contribute a significant amount of nitrous oxide (N₂O) into the atmosphere. Practices to reduce soil N₂O emissions include changing N fertilizer sources and application placement methods.  The objectives of this research were to determine soil surface greenhouse gas (GHG) emissions from a poorly-drained claypan soil, and to assess the impact of urea fertilizer placement on corn (Zea mays L.) production. These strategies consisted of a pre-plant deep band application of urea or urea plus a nitrification inhibitor (NI), nitrapyrin, at a depth of 20 cm compared to pre-plant urea either broadcast (surface-applied) or incorporated to a depth of 8 cm.  The fertilizer application rate was 202 kg N ha^-1.  Field research was initiated in 2014 during which GHGs were sampled frequently throughout the growing season, especially after major rain events, to determine soil surface flux and cumulative emissions of N₂O and carbon dioxide (CO₂). Deep banding of urea in 2014 resulted in the highest cumulative soil N₂O emissions compared to the other treatments, producing roughly 100 g N₂O-N ha^-1 over the growing season. Deep banding urea with NI had the highest cumulative CO₂ emissions, producing nearly 11 kg CO₂-C ha^-1 over the growing season. Incorporating urea to a depth of 8 cm, deep banding urea, and deep banding urea with NI increased yields 940 to 1944 kg ha^-1 compared to the non-treated control and surface broadcast urea treatment.  Urea fertilizer placement had an effect on both soil GHG emissions and corn growth.