Tillage and Nitrogen Source Impacts on Relationships between Nitrous Oxide Emission and Nitrogen Recovery Efficiency in Corn.

Quantitative understanding of relationships between NO emission and plant N uptake are needed to select environmentally optimal management systems for corn ( L.) production. Studies were conducted from 2014 to 2016 in Indiana to assess long-term tillage and N source effects on NO emission, and in 2015 and 2016 on relationships between NO losses and N recovery efficiency (NRE) and N use efficiency (NUE), in a continuous corn system. Tillage treatments (mostly in place since 1975) consisted of no till (NT), strip till (ST), chisel plow (CP), and moldboard plow (MP), whereas the N source comparison involved sidedress urea ammonium nitrate applied at 220 kg N ha with and without nitrapyrin. Grain yield averaged 6.5% greater for MP than for CP and NT in the 3-yr period. Nitrapyrin never increased grain yield or NRE but reduced cumulative seasonal NO emission in 1 yr. Tillage affected NO emission in 2 of 3 yr, when emissions decreased in the order MP > CP > ST > NT. Significant negative linear relationships existed between NO emission and NRE under NT and ST, and between NO and NUE under ST, but not for CP and MP. Overall, NO losses under ST and NT decreased by 17 and 13 g N ha, respectively, per unit increase of NRE, and by 63 g N ha per unit increase of NUE under ST. Our results confirmed that selected management systems such as NT or ST that improved NRE and/or NUE can potentially reduce NO emissions during continuous corn production.