ORIGINAL ARTICLE Assessing the sensitivity of modelled estimates of N 2 O emissions and yield to input uncertainty at a UK cropland experimental site using the DailyDayCent model N. Fitton • A. Datta • K. Smith • J. R. Williams • A. Hastings • M. Kuhnert • C. F. E. Topp • P. Smith Received: 7 January 2014 / Accepted: 26 May 2014 / Published online: 1 June 2014 Ó Springer Science+Business Media Dordrecht 2014 Abstract Biogeochemical models such as Daily- DayCent (DDC) are increasingly used to help quantify the emissions of green-house gasses across different ecosystems and climates. For this use they require parameterisation to represent a heterogeneous region or are site specific and scaled upwards. This requires information on inputs such as climate, soil, land-use and land management. However, each input has an associated uncertainty, which propagates through the model to create an uncertainty in the modelled outputs. To have confidence in model projections, an assess- ment of how the uncertainty in inputs propagated through the model and its impact on modelled outputs is required. To achieve this, we used a pre-defined uncertainty range of key inputs; temperature, precip- itation, clay content, bulk density and soil pH, and performed a sensitivity and uncertainty analysis, using Monte Carlo simulations. This allowed the effect of measurement uncertainty on the modelled annual N 2 O emissions and crop yields at the Grange field exper- imental site to be quantified. Overall the range of model estimates simulated was relatively high and while the model was sensitive to each input parameter, uncer- tainty was driven by the sensitivity to soil pH. This decreased as the N fertiliser application rate increased, as at lower N application rates the model becomes more sensitive to other drivers of N mineralisation such as soil and climate inputs. Therefore, while our results indicate that DDC can provide a good estimate of annual N 2 O emissions and crop yields under UK conditions, reducing the uncertainty in the input parameters will lead to more accurate simulations. Keywords DailyDayCent  N 2 O emissions  Crop yields  Sensitivity analysis  Monte Carlo simulations Introduction Since the beginning of the industrial revolution there has been a 19 % increase in the concentration of nitrous oxide (N 2 O) in the atmosphere (WMO 2010). N 2 O is an important greenhouse gas (GHG) due to its global N. Fitton (&)  A. Datta  A. Hastings  M. Kuhnert  P. Smith Institute of Biological and Environmental Sciences, University of Aberdeen, Cruickshank Building, 23 St. Machar Drive, Aberdeen AB24 3UU, Scotland, UK e-mail: n.fitton@abdn.ac.uk A. Datta Center for Environmental Studies, Earth Sciences and Climate Change Division, The Energy and Resources Institute, Darbari Seth Block, India Habitat Center, New Delhi 110003, India K. Smith  J. R. Williams ADAS, Battlegate Road, Boxworth, Cambridge CB23 4NN, UK C. F. E. Topp SRUC Edinburgh, West Mains Road, Edinburgh EH9 3JG, UK 123 Nutr Cycl Agroecosyst (2014) 99:119–133 DOI 10.1007/s10705-014-9622-0