title: Evaluation of Intensive "4R" Strategies for Decreasing Nitrous Oxide Emissions and Nitrogen Surplus in Rainfed Corn.
abstract: The "4R" approach of using the right rate, right source, right timing, and right placement is an accepted framework for increasing crop N use efficiency. However, modifying only one 4R component does not consistently reduce nitrous oxide (NO) emissions. Our objective was to determine if N fertilizer applied in three split applications (Sp), by itself or combined with changes in N source and rate, could improve N recovery efficiency (NRE) and N surplus (NS) and decrease NO emissions. Over two corn ( L.) growing seasons in Minnesota, NO emissions ranged from 0.6 to 0.9 kg N ha. None of the treatment combinations affected grain yield. Compared with urea applied in a single application at the recommended N rate, Sp by itself did not improve NRE or NS and did not decrease NO. Combining Sp with urease and nitrification inhibitors and/or a 15% reduction in N rate increased NRE from 57 to >73% and decreased NS by >20 kg N ha. The only treatment that decreased NO (by 20-53%) was Sp combined with inhibitors and reduced N rate. Emissions of NO were more strongly correlated with NS calculated from grain N uptake ( = 0.61) compared with whole-plant N uptake ( = 0.39), possibly because most N losses occurred before grain filling. Optimizing both application timing and N source can allow for a moderate reduction in N rate that does not affect grain yield but decreases NO. Grain-based NS may be a more useful indicator of NO emissions than whole-plant-based NS.
authors.forename: Rodney T
authors.initials: RT
authors.lastname: Venterea
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Coulter
authors.forename: Michael S
authors.initials: MS
authors.lastname: Dolan
mesh_terms: D005308:Fertilizers; D009584:Nitrogen; D009609:Nitrous Oxide / Q000032:analysis*; D014508:Urea; D003313:Zea mays
chemical_list: D005308:Fertilizers; D014508:Urea; D009609:Nitrous Oxide; D009584:Nitrogen