Key role of efficient nitrogen application in low carbon agriculture

Low carbon agriculture is an inevitable trend for sustainable intensive agriculture in China. Efficient nitrogen fertilization is the key driving factor for achieving low carbon agriculture, understanding that will help the integration and optimization of agricultural management measures, achieving the goals of soil carbon sequestration, greenhouse gas mitigations and yield improvement, and thus to sustain intensive low carbon agriculture. Low carbon agriculture has experienced three development stages from the points of connotation and research methods. The initial stage was developed from total global warming potentials of greenhouse gas emissions from croplands, then the concept was changed to net global warming potentials covering greenhouse gas emissions and soil carbon sequestration, now is focused on the net total global warming potentials with additional carbon emissions derived from field management and chemical inputs and then to yield scaled greenhouse gas intensity associated with life cycle assessment. Moreover, net ecosystem carbon budget and soil carbon sequestration were developed from conventional long term field experiment to the current crop seasonal scale short term field experiment. Based on the crop seasonal scale soil carbon sequestration and life cycle assessment, the net total global warming potential and yield-scaled greenhouse gas intensity were fully developed as well. As a case study of life cycle assessment and net ecosystem carbon budget, we analyzed the contributions of nitrogen fertilization to grain yield, soil carbon sequestration, methane (CH₄) and nitrous oxide (N₂O) emissions and agricultural managements associated carbon emissions under intensive rice-wheat annual rotation system with different scenarios, and thus highlighted the key driving role of efficient nitrogen fertilization in sustainably achieving low carbon agriculture in terms of net total global warming potential and yield scaled greenhouse gas intensity.