Optimizing net greenhouse gas balance of a bioenergy cropping system in southeast China with urease and nitrification inhibitors

• HQ+DCD amendment increased NPP but suppressed soil RH in coastal bioenergy crops.
• HQ+DCD amendment decreasing soil N2O but stimulating CH4 emissions.
• The fertilizer N-induced emission factor of N2O was lowered by use of HQ+DCD.
• HQ+DCD improving the ecosystem CO2 sequestration and GHGs sink strength.

Efforts to advance our knowledge on the potential of bioenergy instead of fossil fuels in terms of mitigating climatic impact are in urgent need. No data is currently available on the use of urease and nitrification inhibitors in costal saline bioenergy cropping systems. An overall accounting of net greenhouse gas balance (NGHGB) and greenhouse gas intensity (GHGI) affected by combined effects of urease inhibitor hydroquinone (HQ) and nitrification inhibitor dicyandiamide (DCD) amendment was examined in a coastal saline Jerusalem artichoke bioenergy cropping system. The net ecosystem exchange of CO2 (NEE) was determined by the difference between soil heterotrophic respiration (RH) and net primary production (NPP) using static chamber method. Urease and nitrification inhibitors amendment increased the NPP but exerted a suppression effect on soil RH over the Jerusalem artichoke cropping system. A trade-off relationship was observed by decreasing soil N2O but stimulating soil CH4 emissions following HQ+DCD amendment. The plots combined urea with HQ+DCD application increased soil CH4 by 167% while decreased N2O by 16% as compared to with urea only in the bioenergy cropping system. On average, the fertilizer N-induced emission factor of N2O was estimated to be 0.25% across the fertilized plots. Compared with urea, the plots with urea and HQ+DCD resulted in a further decrease by 37% and 15% in estimated NGHGB and GHGI over the Jerusalem artichoke cropping system, respectively. Overall, Jerusalem artichoke production would achieve higher biomass as source of biofuels but lower climatic impacts, particularly when together with urease and nitrification inhibitors amendment in coastal saline soils.