Nitrogen management in arable crops: Can available knowledge and tools reconcile agronomic and environmental needs?
Résumé
Nitrogen management in cropping systems must face strong challenges. Substantial progress has been made in understanding the dynamics of nitrogen requirements for diverse crops, the determinants of immobilization and mineralization of nitrogen from organic matter in the soil, and the factors explaining the variability in the use efficiency of nitrogen fertilizers. This knowledge has been integrated in decision-making support tools for nitrogen fertilization as well as in monitoring tools. Such tools aim at satisfying crop nitrogen requirements throughout the crop cycle in order to maximise growth but often lead to periods of excess nitrogen nutrition. More recent knowledge on the effects of temporary nitrogen deficiencies make it possible to reflect upon new paradigms for nitrogen fertilization management. They involve the concept of useful nitrogen deficiency based on the objective of maximizing nitrogen efficiency as a fertilizer and thus minimising environmental losses. Finally, other levers than nitrogen fertilization can be mobilized to take the above mentioned challenges in nitrogen management into account and enlarge the question to the landscape scale.
