Resumen
- Colombia is one of countries with the highest livestock inventory, much of which is in extensive grazing of Brachiaria and Megathyrsus pastures. Some Brachiaria species are natural producers of Biological Nitrification Inhibitors (BNI), which are an alternative mitigation of Greenhouse Gases (GHGs). However, not all tropical grasses have the same quantity of BNI. The GHGs inventory of Colombian livestock needs an approach of nitrous oxide (N2O) emissions to real fluxes. The objective of this research was to evaluate the effect of bovine urine application in the emission of N2O of pastures into dry and rainy periods. The experiment was conducted at the Research Center CORPOICA ”La Libertad” in plots of 2.5 m x 5.0 m with three forage species typical of the region: Brachiaria decumbens, Brachiaria humidicola and Megathyrsus maximus; They were randomized through 4 repetitions per treatment (bovine urine) and forage species. N2O samples were measured in static closed chambers and analyzed by gas chromatography. Sampling times in the chambers were 0, 20 and 40 minutes during year. Temperature and soil moisture, rainfall and relative humidity of environment were sampled. It was observed that the application of urine had no significant effect on N2O emissions, biomass production and protein content of forages (p > 0.05), possibly due to the low nitrogen contribution in the bovine urine. On the contrary, climate season and forage species had effect on these variables (p < 0.05). Rainy season shower lower emissions of N2O due to a higher incidence of negative flows caused by very high humidity (in soil and environment). We conclude B. decumbens and B. humidicola have factors that mitigate N2O emissions, contrary to M. maximus whose N2O flux in the soil was 65% higher than other species tested. This effect also was observed in protein content of the forages.