Udvardi, M., F. E. Below, M. J. Castellano, A. J. Eagle, K. E. Giller, J. K. Ladha, X. Liu, T. M. Maaz, B. Nova-Franco, N. Raghuram, G. P. Robertson, S. K. Roy, M. Saha, S. Schmidt, M. Tegeder, L. M. York, and J. W. Peters. 2021. A research road map for responsible use of agricultural nitrogen. Frontiers in Sustainable Food Systems 5:660155.
Nitrogen (N) is an essential but generally limiting nutrient for biological systems. Development of the Haber-Bosch industrial process for ammonia synthesis helped to relieve N-limitation of agricultural production, fueling the Green Revolution and reducing hunger. However, the massive use of industrial N-fertilizer has doubled the global N-cycle with dramatic environmental consequences that threaten planetary health. Consequently, there is an urgent need to reduce losses of reactive-N from agriculture, while ensuring sufficient N-inputs for food security. Here, we review current knowledge related to N use efficiency (NUE) in agriculture and identify research opportunities in the areas of agronomy, plant breeding, biological N fixation (BNF), soil N-cycling, and modeling to achieve responsible, sustainable use of N in agriculture. Amongst these opportunities, improved agricultural practices that synchronize crop N-demand with soil N-availability are low-hanging fruit. Crop breeding that targets root and shoot physiological processes will likely increase N uptake and utilization of soil N, while breeding for BNF effectiveness in legumes will enhance overall system NUE. Likewise, engineering of novel N-fixing symbioses in non-legumes could reduce the need for chemical fertilizers in agroecosystems but is a much longer-term goal. The use of simulation modeling to conceptualize the complex, interwoven processes that affect agroecosystem NUE, along with multi-objective optimization, will also accelerate NUE gains.
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