Legume Proportion of Grass-Legume Mixtures Affects Greenhouse Gas Emissions from Animals Grazing Pasture

View the project final report

• 2016 annual report

Commodities

• Agronomic: Rhizoma peanut, bahiagrass
• Animals: bovine

Practices

• Animal Production: feed/forage, grazing management, Greenhouse gas emissions

We are comparing legume- and grass-based beef production systems in terms of greenhouse gas emissions from animal urine and dung, and potential methane emissions from enteric fermentation. Typically enteric fermentation emissions in legume-based diets are less than those of animals grazing pure grass pastures, however greater nitrogen content in diets containing legumes may increase emissions of some greenhouse gases (such as nitrous oxide) from animal excreta. The first year of field experimentation was completed in October 2015, and laboratory and data analysis are ongoing.

1. To quantify emissions of N₂O and CH₄ from animal dung and N₂O from animal urine for these two pasture types in order to obtain emission factors of N₂O separately for each excreta type (urine or dung) and for animals with contrasting diets, and to compare emission factors obtained in this study with others reported for different production systems in the literature and those used by the IPCC model;
2. To quantify enteric fermentation CH₄ emissions from the two pasture types and compare these measurements with those estimated by the IPCC model with parameters currently used for Southeast US in order to assess the prediction capability of the model;
3. To sum emissions of N₂O from dung and urine and CH₄ from dung and enteric fermentation of animals grazing the two pasture types and use global warming potential to estimate emissions in CO₂e.