Greenhouse gas implications of leucaena-based pastures. Can we develop an emissions reduction methodology for the beef industry?

Nigel Tomkins,Stuart Denman,Ed Charmley,Chris S Mcsweeney,Cristopher J Lambrides,Matthew Harrison,Ram Dalal

doi:10.17138/tgft(7)267-272

Abstract

Keynote paper presented at the International Leucaena Conference, 1‒3 November 2018, Brisbane, Queensland, Australia.The perennial legume leucaena (Leucaena leucocephala) is grown across the subtropics for a variety of purposes including livestock fodder. Livestock in Australia emit a significant proportion of the methane produced by the agriculture sector and there is increasing pressure to decrease emissions from beef cattle production systems. In addition to direct productivity gains for livestock, leucaena has been shown to lower enteric methane production, suggesting an opportunity for emissions mitigation and Commonwealth Emissions Reduction Fund (ERF) methodology development, where leucaena browse is adopted for high value beef production. Determining the proportion of leucaena in the diet may be one of the more challenging aspects in attributing mitigation. Current enteric emission relationships for cattle consuming mixed grass-leucaena diets are based on intensive respiration chamber work. Herd-scale methane flux has also been determined using open path laser methodologies and may be used to validate an on-farm herd-scale methodology for leucaena feeding systems. The methodology should also address increased potential for soil organic carbon storage by leucaena grazing systems, and changes in nitrous oxide production. This paper outlines the background, justification, eligibility requirements and potential gaps in research for an emissions quantification protocol that will lead to the adoption of a leucaena methodology by the Australian beef industry. Development of a methodology would be supported by research conducted in Australia.

Highlights

The perennial leguminous shrub leucaena (Leucaena leucocephala) is grown across the tropical and subtropical regions of South/Southeast Asia and northern Australia for livestock fodder, nitrogen fixation, firewood and paper pulp (Shelton and Brewbaker 1994)
Livestock in Australia emit a significant proportion of the methane produced by the agriculture sector and there is increasing pressure to decrease emissions from beef cattle production systems
A proposed methodology is supported by research conducted under the National Livestock Methane Program (MLA 2015a), modelling work undertaken under the Whole Farm Systems Abatement Modelling program (WFM 2017) and a series of independent studies

Summary

Introduction

The perennial leguminous shrub leucaena (Leucaena leucocephala) is grown across the tropical and subtropical regions of South/Southeast Asia and northern Australia for livestock fodder, nitrogen fixation, firewood and paper pulp (Shelton and Brewbaker 1994). Recent research has demonstrated additional benefits in the form of potential reduction of enteric methane production and increased soil carbon (C) storage, implying that the shrub may reduce greenhouse gas (GHG) emissions at the farm level (McSweeney and Tomkins 2015; Harrison et al 2015; Vercoe 2015; Conrad et al 2017). This presents an emissions-mitigation opportunity that would apply across the industry where leucaena is managed. Kennedy and Charmley (2012) demonstrated that the level of readily fermentable crude protein (RFCP) in legumes can be negatively correlated with methane production. The duration of leucaena feeding and intake or proportion of the diet will be critical in revising the Herd Management Calculator (http://bit.ly/2SZf2qI)

Increased soil carbon storage opportunities

Rumen microbial structure and function of leucaenafed cattle

Findings

Conclusions