Effects of Ecological Intensification and Late-Split N Timing on the Relationship Between Nitrous Oxide Emission and Nitrogen Recovery Efficiency in Corn.

Ecological intensification (EI) has been advocated as soil management option to increase yield from the same amount of available farmland with minimum negative environmental impact.  However, little research has been conducted to evaluate the effects of ecological intensification on nitrous oxide (N₂O) emission, and the relationship between N₂O emission and nitrogen (N) recovery efficiency (NRE).  Experiments were conducted over 2 cropping seasons, to assess the effects of ecological intensification (EI) on seasonal N₂O emission and the relationship between N₂O emission and NRE, relative to farmer’s practice (FP) during corn production in Indiana.  The EI treatments involved increased plant population (96,000 plants ha^-1) managed at 3 N rates: 0, 180, and 240 kg N ha^-1 with nitrapyrin, and FP consisted of lower population (74,000 plants ha^-1) managed at 0, 112, and 180 kg N ha^-1 without nitrapyrin. Gas samples were collected twice weekly for 6 weeks following N application, and weekly thereafter till corn maturity and seasonal N₂O emission was determined.  At maturity, corn was harvested and above ground N uptake determined for both stover and grain.  The EI management, even at 240 kg N application (with nitrapyrin) reduced N₂O emissions by up to 12% compared to the highest level of FP at 180 kg N rate in 2015, and emission was not significantly different for both treatments in 2016.  A relatively weak (r² = 0.42), but negative linear relationship existed between N₂O and NRE across treatments in the EI/FP, and suggested that N₂O emission was likely to be reduced as NRE increased for these management systems.