Deep N fertilizer placement mitigated N2O emissions in a Swedish field trial with cereals
Katrin Rychel, Katharina Meurer, Gunnar Börjesson, Monika Strömgren, Gizachew Tarekegn Getahun, Holger Kirchmann, Thomas Kätterer
Abstract
Abstract Deep fertilizer placement is a proposed strategy to increase crop yield and nitrogen (N) use efficiency while decreasing nitrous oxide (N 2 O) emissions from soil to atmosphere. Our objective was to test three fertilization depth orientations to compare overall N use efficiency, based on a 2-year field trial on a mineral soil cropped with cereals in Uppsala, Sweden. The field was fertilized with ammonium nitrate at a rate of 120 kg ha −1 (2016) and 105 kg ha −1 (2017) and a deep fertilizer placement (DP) at 0.20 m was compared to a shallow placement (SP) at 0.07 m and a mixed-depth placement (MP) where fertilizer was halved between the depths of 0.07 and 0.20 m, and a non-fertilized control (NF). In 2016, compared to SP, MP and DP increased N content in harvested grain by 3.6% and 2.5% respectively, and DP increased grain yield by 11% ( P < 0.05). In both years, N 2 O emissions were similar in DP and NF, whereas SP and MP emissions were similar but generally higher than those in DP and NF. Fertilizer-induced emission factors (EF) for the growing season of 2017 decreased with fertilizer placement depth and were 0.77 ± 0.07, 0.58 ± 0.03, and 0.10 ± 0.02 for SP, MP, and DP, repectively. Although deep N placement benefits are likely dependent on weather conditions and soil type, this strategy has a clear potential for mitigating N 2 O emissions without adversely affecting yield.