Nitrogen-loss and carbon-footprint reduction by plant-rhizosphere exudates.

Small rhizosphere exudates as chemical signals provide a green strategy to reduce nitrogen emissions and promote low-carbon agriculture. Specific biological nitrification inhibitors (BNIs) and biological denitrification inhibitors (BDIs) could retard nitrification and denitrification, thus reducing N 2 O emissions from terrestrial ecosystems. Enhanced nitrogen removal rates and lower N 2 O emissions are achieved by biological denitrification promoters (BDPs), such as root-derived fatty acid amides and sterols, and microbe-derived N -acyl-homoserine lactones (AHLs) in aquatic environments. Cultivating BNI/BDI/BDP-enhanced plant varieties, intercropping and rotation with BNI/BDI plants, developing green nitrogen fertilizers, and designing water purification bioagents based on small rhizosphere exudates are promising application measures for supporting green low-carbon agriculture. Low-carbon approaches to agriculture constitute a pivotal measure to address the challenge of global climate change. In agroecosystems, rhizosphere exudates are significantly involved in regulating the nitrogen (N) cycle and facilitating belowground chemical communication between plants and soil microbes to reduce direct and indirect emissions of greenhouse gases (GHGs) and control N runoff from cultivated sites into natural water bodies. Here, we discuss specific rhizosphere exudates from plants and microorganisms and the mechanisms by which they reduce N loss and subsequent N pollution in terrestrial and aquatic environments, including biological nitrification inhibitors (BNIs), biological denitrification inhibitors (BDIs), and biological denitrification promoters (BDPs). We also highlight promising application scenarios and challenges in relation to rhizosphere exudates in terrestrial and aquatic environments. [ABSTRACT FROM AUTHOR]