Emission factors of nitrous oxide as a greenhouse gas from cattle manure in tropical pasture and supplemented

Abstract

The growth in livestock production increases the deposition of cattle manure and, consequently, greenhouse gas emissions (GHG). Supplementation emerges as a strategy to mitigate these emissions by modifying the composition of excreta. The objective of this study was to determine the nitrous oxide emission factors (EF) by investigating the relationship between applied excreta and GHG emissions from the urine and feces of grazing cattle supplemented or not. The experiment was conducted in a randomized block design with four treatments and four replicates, using urine (U) and feces (F) samples from cattle grazing forage sorghum (G) and forage sorghum with supplementation (G+S), forming the treatments UG, UG+S, FG and FG+S. GHG fluxes were obtained from collections using the static chamber methodology, consisting of a base and a galvanized steel chamber. Air samples were collected in four separate time points. The nitrous oxide emission factor (EF) was calculated based on the difference between the cumulative emissions from the treatment and the control, divided by the amount of nitrogen applied. The data were subjected to a normality test, followed by analysis of variance and Tukey test at a 5% significance level. No significant differences were observed among the treatments, with EF (%) means of 1.1096 (UG+S), 0.9591 (UG), 0.2923 (FG), and 0.2140 (FG+S). Dietary changes did not cause sufficient changes in excreta to alter emission factors. It was concluded that nitrous oxide emission factors did not differ between supplemented and non-supplemented cattle in tropical grazing systems.