Impacts of Leucaena plantations on greenhouse gas emissions and carbon sequestration in northern Australian cattle production systems

Summary

The project was conducted with steers grazing established Leucaena or grass pastures to determine the impact on herd scale methane emissions, productivity and rumen function.

Relative emissions from cattle with access to Leucaena appeared lower, particularly in the months following the wet season, compared with those grazing grass dominated pastures. Rumen microbial analysis showed Leucaena diets increased the relative abundance of methyl group-utilising Methanosphaera while decreasing the proportion of other functional groups of methanogens. In Leucaena fed cattle there was a shift in the bacterial populations and fermentation to more reduced end products which may contribute along with leucaena tannins to decreased methane emissions.

The effects of Leucaena-finishing cattle on emissions, production and profitability at the whole farm level was modelled using the Beef Greenhouse Accounting Framework and the resultant carbon offset income determined relative to baseline data assuming two C prices ($/t CO2-e). Finishing steers on Leucaena effectively increased animals carried and liveweight turnoff by 15% and 31%, respectively.

The addition of Leucaena to beef production systems has the potential to increase productivity and gross margin, whilst reducing emissions intensity. Provided net farm emissions are maintained or reduced, Leucaena appears conducive to sustainable intensification of beef production in tropical grazing systems.