Contents lists available at ScienceDirect Agriculture, Ecosystems and Environment journal homepage: www.elsevier.com/locate/agee N 2 O emissions from maize production in South-West Germany and evaluation of N2O mitigation potential under single and combined inhibitor application Sebastian Weller a,b, ⁎ , Alfred Fischer b , Georg Willibald b , Barbara Navé c , Ralf Kiese b a Multidisciplinary Institute for Plant Biology (CONICET-UNC), Av. Vélez Sársfield 1611(X5000HVA), Ciudad Universitaria, 5000, Córdoba, Argentina b Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Atmospheric Environmental Research. Kreuzeckbahnstr. 19, 82467, Garmisch- Partenkirchen, Germany c BASF SE, 67117 Limburgerhof, Germany ARTICLE INFO Keywords: Maize Nitrous oxide Urease inhibitor Denitrification inhibitor Pyraclostrobin NBPT/NPPT ABSTRACT In a study on the emissions of nitrous oxide (N 2 O) from maize production in South-West Germany, N 2 O emis- sions where measured with an automated chamber system over two consecutive cropping seasons, including an intermediate fallow period. Urea-based fertilizer treatments included a fertilizer only control (U), as well as the use of pyraclostrobin, which showed inhibitory effects on denitrification in a laboratory experiment. Pyraclostrobin was used alone (U + P) and in combination with a NBPT/NPPT urease inhibitor (UI + P) and a reduced fertilizer rate (70% UI + P). The U control emitted 1.03 ± 0.22 and 1.94 ± 0.61 kg N 2 O-N ha -1 in the cropping seasons of 2012 and 2013, respectively. Fallow emissions mainly occurred after a soil freeze-thaw period and were 0.24 ± 0.08, 0.23 ± 0.09, 0.22 ± 0.06, 0.32 ± 0.21 kg N 2 O-N ha -1 for U, 70% UI + P, U + P and UI + P, respectively. In the cropping season 2012, no effects of the UI + P and U + P treatments could be observed. In 2013, UI + P increased N 2 O emissions by 13% when compared to the U control, while a significant reduction of 24% was observed for the U + P treatment. The 70% UI + P treatment resulted in significantly lower (∼30%) N 2 O emissions and only slight reductions (7–10%) of grain yields in both years. Climate conditions varied strongly between seasons (416 and 704 mm total rainfall in 2012 and 2013, respec- tively) which most likely also influenced the performance of the inhibitors. Direct emission factors (EF d %) also increased strongly in 2013 (0.28 ± 0.12 in 2012 vs. 0.94 ± 0.41 in 2013 for U) but were generally lower than the 1% IPCC default value. Values for nitrogen recovery efficiency and yield-scaled N 2 O emissions were most preferable for the 70% UI + P treatment and indicate that reduced fertilizer rates in combination with inhibitors could represent a viable means for N 2 O mitigation without significant yield penalties in agricultural systems. 1. Introduction Since the invention of the Haber-Bosch process in the early 20th century, the use of synthetic Nitrogen (N) fertilizer has increased steadily, following the global expansion of arable land and the in- tensification of agricultural cropping systems (Erisman et al., 2007; Gruber and Galloway, 2008). Additional N input for crop production via mineral fertilizers achieve higher yields and better food quality (Harrison and Webb, 2001; Tilman et al., 2002). However, this practice does also have a downside, namely surplus N not used by plants and thus emitted into the atmosphere or leached into water bodies with harmful effects on the environment (Fan et al., 2012). Within these possible byproducts of N-fertilization, especially nitrous oxide (N 2 O) has a great impact on the climate, as it has a global warming potential (GWP 100 ) 298 times higher than carbon dioxide (CO 2 ) and is currently the single most important substance for stratospheric ozone depletion (IPCC, 2013; Portmann et al., 2012; Robertson et al., 2000). Estimations hold agriculture responsible for 10–12% of total global anthropogenic emissions of greenhouse gases (GHG), including 60% of global N 2 O emissions, mainly originating from fertilizer applications to soils (Smith et al., 2007; WRI, 2014). As rising atmospheric N 2 O concentrations are primarily linked to land conversion for agriculture and the intensified use of nitrogen fertilizers (Syakila and Kroeze, 2011; Ussiri and Lal, 2013) further increases can be expected due to the growing demand for https://doi.org/10.1016/j.agee.2018.10.004 Received 14 February 2018; Received in revised form 28 June 2018; Accepted 9 October 2018 ⁎ Corresponding autor. E-mail addresses: sweller@imbiv.unc.edu.ar (S. Weller), alfred.fischer@kit.edu (A. Fischer), georg.willibald@kit.edu (G. Willibald), barbara.nave@basf.com (B. Navé), ralf.kiese@kit.edu (R. Kiese). Agriculture, Ecosystems and Environment 269 (2019) 215–223 0167-8809/ © 2018 Published by Elsevier B.V. T