How do greenhouse gas emissions vary with biofertilizer type and soil temperature and moisture in a tropical grassland?

Abstract

Greenhouse gases are known to play an important role in global warming. In this study, we determined the effects of selected soil and climate variables on nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) emissions from a tropical grassland fertilized with chicken slurry, swine slurry, cattle slurry, and cattle compost. Cumulative N2O emissions did not differ between treatments and varied from 29.26 to 32.85 mg N m(-2). Similarly, cumulative CH4 emissions were not significantly different among the treatments and ranged from 6.34 to 57.73 mg CH4 m(-2). Slurry and compost application induced CO2 emissions that were significantly different from those in the control treatment. The CH4 conversion factors measured were 0.21%, 1.39%, 4.39%, and 5.07% for cattle compost, chicken slurry, swine slurry, and cattle slurry, respectively, differing from the recommendations of the Intergovernmental Panel on Climate Change (IPCC). The fraction of added N emitted as N2O was 0.39%, which was lower than the IPCC default value of 2%. Our findings suggest that N2O emissions could be mitigated by replacing synthetic fertilizer sources with either biofertilizer or compost. Our results indicate the following: N2O emission was mainly controlled by soil temperature, followed by soil moisture and then soil NH4 content; CH4 fluxes were mainly controlled by soil moisture and chamber headspace temperature; and CO2 fluxes were mainly controlled by chamber headspace temperature and soil moisture.