Agronomic and physiological aspects of nitrogen use efficiency in conventional and organic cereal-based production systems

Abstract

AbstractBetter management of synthetic nitrogen (N) fertilizers in conventional agricultural systems laid the foundation for feeding the increasing world's population since the Green Revolution. However, excessive reliance on inorganic fertilizer has resulted in environmental degradation issues. Difficulties in soil nutrition management in organic cropping systems often results in lower and variable yields, also raising questions of sustainability. Improving nitrogen use efficiency (NUE) is thus of key importance to overcome environmental concerns in conventional systems and production limitations in organic systems. The differences in the two farming systems have impacts on crop traits and N cycles, making it difficult to enhance NUE with a single strategy. Different approaches need to be adopted to improve NUE in each system. Extensive efforts have been made to better understand mechanisms to potentially improve NUE in cereal crops under both systems. This review suggests that NUE may be improved through a combination of management practices and breeding strategies specific to the management system. Diversified crop rotations with legumes are effective practices to optimize the N cycle in both conventional and organic systems. Best Management Practices coupled with nitrification inhibitors, controlled release products and split-application practices can reduce N loss in conventional systems. In organic systems, we need to take advantage of available N sources and adapt practices such as no-tillage, cover crops, and catch crops. Utilization of beneficial soil microorganisms is fundamental to optimizing availability of soil N. Estimation of soil organic matter mineralization using prediction models may be useful to enhance NUE if models are calibrated for target environments. Cereal crops are often bred under optimum N conditions and may not perform well under low N conditions. Thus, breeders can integrate genetic and phenotypic information to develop cultivars adapted to specific environments and cultivation practices. The proper choice and integration of strategies can synchronize N demand and supply within a system, resulting in reduced risk of N loss while improving NUE in both conventional and organic systems.