Does Nitrogen Fertilizer Application Rate to Corn Affect Nitrous Oxide Emissions from the Rotated Soybean Crop?

Abstract

<p>Little information exists on the potential for N fertilizer application to corn (<em>Zea mays</em> L.) to affect N₂O emissions during subsequent unfertilized crops in a rotation. To determine if N fertilizer application to corn affects N₂O emissions during subsequent crops in rotation, we measured N₂O emissions for 3 yr (2011–2013) in an Iowa, corn–soybean [<em>Glycine max</em> (L.) Merr.] rotation with three N fertilizer rates applied to corn (0 kg N ha⁻¹, the recommended rate of 135 kg N ha⁻¹, and a high rate of 225 kg N ha⁻¹); soybean received no N fertilizer. We further investigated the potential for a winter cereal rye (<em>Secale cereale</em> L.) cover crop to interact with N fertilizer rate to affect N₂O emissions from both crops. The cover crop did not consistently affect N₂O emissions. Across all years and irrespective of cover crop, N fertilizer application above the recommended rate resulted in a 16% increase in mean N₂O flux rate during the corn phase of the rotation. In 2 of the 3 yr, N fertilizer application to corn (0–225 kg N ha⁻¹) did not affect mean N₂O flux rates from the subsequent unfertilized soybean crop. However, in 1 yr after a drought, mean N₂O flux rates from the soybean crops that received 135 and 225 kg N ha⁻¹ N application in the corn year were 35 and 70% higher than those from the soybean crop that received no N application in the corn year. Our results are consistent with previous studies demonstrating that cover crop effects on N₂O emissions are not easily generalizable. When N fertilizer affects N₂O emissions during a subsequent unfertilized crop, it will be important to determine if total fertilizer-induced N₂O emissions are altered or only spread across a greater period of time.</p>