Impacts of slurry application methods and inhibitors on gaseous emissions and N2O pathways in meadow-cinnamon soil

Abstract

This study aimed to evaluate the impact of mitigation practices (slurry application methods and inhibitors applications) on gas emissions and identify the soil N₂O production pathways in cattle slurry applied soil using isotopocule mapping approach. First, we compared the NH₃ and N₂O emissions of cattle slurry applied soil in a summer maize field experiment in north China plain (NCP) with four treatments: control (CK, no fertilization), slurry application using surface (SA-S), slurry application using band application (BA-S), and chemical fertilizer application using band application (BA-C). Then, an incubation experiment was conducted to investigate the mitigation effect of nitrification inhibitors (dicyandiamide, DCD) and denitrification inhibitors (procyanidins, PC) and their combination (DCD + PC) on gaseous N emissions with slurry applied using incorporation (IA) or surface application (SA) methods. The results showed that the total gaseous N emissions (N₂O-N and NH₃-N) in field were in the order of SA-S (1534 mg m^-2) > BA-S (338 mg m^-2) > BA-C (128 mg m^-2) > CK (55 mg m^-2), and the dominant N loss contributor varied from NH₃ in SA-S (∼89%) to N₂O in BA-S (∼94%) and BA-C (∼88%). Moreover, the isotopocule mapping approach indicated that emitted N₂O of the slurry applied soil in field appeared to have lower r_N2O values and led to more N₂O + N₂ emissions at the initial fertilization period. The incubation experiment indicated that the N₂O emissions of slurry-applied soil were significantly reduced by DCD (∼45%) and DCD + PC (∼67%) application in comparison with CK (p < 0.05), and the stronger contributions of bacterial denitrification/nitrifier denitrification to N₂O production were revealed by the lower δ¹⁵N^SP in N₂O using the isotopocule mapping approach. In conclusion, in NCP the gaseous losses of the slurry applied field can be largely reduced by using incorporation method, and greater reduction could be achieved given the simultaneous application of nitrification/denitrification inhibitors.

Keywords: Animal slurry; Dicyandiamide; Gaseous nitrogen loss; Isotopocule mapping approach; Procyanidins.