Articles | Volume 13, issue 19
https://doi.org/10.5194/bg-13-5433-2016
https://doi.org/10.5194/bg-13-5433-2016
Research article
 | 
30 Sep 2016
Research article |  | 30 Sep 2016

Quantifying nitrogen losses in oil palm plantations: models and challenges

Lénaïc Pardon, Cécile Bessou, Nathalie Saint-Geours, Benoît Gabrielle, Ni'matul Khasanah, Jean-Pierre Caliman, and Paul N. Nelson

Abstract. Oil palm is the most rapidly expanding tropical perennial crop. Its cultivation raises environmental concerns, notably related to the use of nitrogen (N) fertilisers and the associated pollution and greenhouse gas emissions. While numerous and diverse models exist to estimate N losses from agriculture, very few are currently available for tropical perennial crops. Moreover, there is a lack of critical analysis of their performance in the specific context of tropical perennial cropping systems. We assessed the capacity of 11 models and 29 sub-models to estimate N losses in a typical oil palm plantation over a 25-year growth cycle, through leaching and runoff, and emissions of NH3, N2, N2O, and NOx. Estimates of total N losses were very variable, ranging from 21 to 139 kg N ha−1 yr−1. On average, 31 % of the losses occurred during the first 3 years of the cycle. Nitrate leaching accounted for about 80 % of the losses. A comprehensive Morris sensitivity analysis showed the most influential variables to be soil clay content, rooting depth, and oil palm N uptake. We also compared model estimates with published field measurements. Many challenges remain in modelling processes related to the peculiarities of perennial tropical crop systems such as oil palm more accurately.

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Short summary
Oil palm is the most rapidly expanding tropical perennial crop, which raises environmental concerns, notably related to the use of nitrogen fertilisers and consequent pollution. We tested existing models to estimate N losses in plantations. Results were highly variable and highlighted the remaining challenges to improve the reliability of these models in order to steer towards more sustainable practices.
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