Leucaena & the Environment
Leucaena has some very important environmental benefits:
1. Nitrogen fixed by Leucaena reverses nitrogen run-down and improves soil fertility and promotes better grass growth within the vicinity of the legume. This results in improved animal production.
2. Leucaena grown in association with a vigorous and adapted grass (e.g. Buffel, Rhodes, Green Panic) will help to prevent soil erosion.
3. The deep rooting habit of Leucaena can extract water from the soil to a depth of 3 - 5 metres thus preventing rising water tables that can bring salt to the surface and cause dry land salinity.
4. As a woody-stemmed tree, Leucaena acts as a carbon sink by sequestering significant amounts of carbon from the atmosphere in its woody frame and in additional soil organic matter, stimulating soil biological activity and improving the soil structure.
5. The effects of Leucaena-finishing cattle on greenhouse gas emissions, production and profitability at the whole farm level has been modelled using the Beef Greenhouse Accounting Framework. Finishing steers on Leucaena has been shown to effectively increase animals carried and liveweight turnoff by 15% and 31%, respectively compared to grass pastures. The National Livestock Methane Program determined that average methane output (g/kg live weight gain) was 28% less on Leucaena – grass pastures compared to grass (Rhodes) only pastures.
Leucaena as a weed: a word of caution
Leucaena produces viable seed and can cause weed problems in ungrazed areas such as gullies, banks of watercourses and road verges. The 'common' Leucaena (i.e. L. leucocephala ssp. leucocephala) that arrived here over 120 years ago has shown this. The cultivated ssp. glabrata cultivars will also colonise ungrazed areas if they are allowed to escape from grazed plantations and precautions should be taken to prevent this.
The Leucaena Network recognised this and developed the Leucaena CODE OF PRACTICE in August 2000. The Code is promoted widely among growers and highlights the need to manage Leucaena to minimise the risk of escape and to control any plants that move from the planted area. This CODE is consistent with the Queensland Government’s policy to reduce the weed threat of Leucaena that was adopted four years later in November 2004.
The Leucaena is currently working with producers, State, Territory and local Governments to ensure the Code of Practice meets today's changing environmental requirements.
LEUCAENA AND CARBON
The Leucaena Network hosted a very successful Leucaena Carbon Forum in Rockhampton, Central Queensland on Tuesday 26 October 2021. Thank you to MLA and CQU for the support of the Forum, to all presenters and speakers and to all who attended.
CONTROLLING ROGUE LEUCAENA
The removal of 'rogue' leucaena, that is leucaena that has established in areas other than where it was planted, requires the removal or killing of the plant's root system. This can be through either chemical or mechanical means.
Unwanted leucaena can be controlled through the application of Access Herbicide (Triclopyr and Picloram) with Diesel as the surfactant at a rate of 1:60. Access is a specialised herbicide for control of woody weeds and is suitable for use in environmentally sensitive situations. Access is applied to the cut stump of the plant, immediately after the trunk is cut. Alternatively, it may be applied by spraying the full circumference of the trunk or stem of the plant.
The Access SDS may be viewed here and videos demonstrating the application methods of Access are
Mechanical removal must ensure the plant roots are removed to prevent resprouting. Blade ploughing or cutter-barring to sever the root system is an option.