Greenhouse gases emissions from tropical grasslands affected by nitrogen fertilizer management

Greenhouse gases (GHGs) emissions from livestock systems are important because of their significant contribution to global warming. Nitrogen fertilization can improve system production; however, it alters soil gas emissions. We evaluated soil nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) emissions to investigate how they are affected by increasing levels of N fertilizer (urea) in a productive Marandu grass [Urochloa brizantha (Hochst ex A. Rich) Stapf] pasture subjected to continuous grazing by young Nellore beef cattle (Bos indicus). The N2O, CH4, and CO2 emissions were significantly affected by increasing N fertilizer levels. The seasons also affected GHGs emissions. Nitrogen fertilizer favored CH4 consumption relative to the control plot without N, with mean emission of 23.7 mu g CH4-C m(-2) h(-1) in the fertilized plots compared to 61.6 mu g CH4-C m(-2) h(-1) in the control. The N-fertilized areas presented higher CO2 emissions compared to the control plot without N. The areas that received N fertilization showed a positive linear association between the water-filled pore space and N2O emission. Soil temperature drove CO2 emissions. Increasing N fertilization in grazed marandu grass increases N2O and CO2 emissions during the growing season, while reducing CH4. The effect of fertilization during the transition season was not apparent, and perhaps other factors could provide a better explanation for the GHG emissions during this period.