Leguminosae

Common names

Mulga (Australia).

Description

There are four forms:

• Low mulga: 

shrub with short, spurlike branches, kept trimmed on top by continual grazing by sheep and cattle. It is useful for grazing but a poor source of drought feed because of its low yield per hectare.

• Whipstick mulga: 

immature stands of thin trees, close together, with leaves only in the upper part. These are best utilized by pushing with a bulldozer or pulling with cable or chain.

• Umbrella mulga: 

mature trees, branched and very leafy. Vary considerably in palatability; respond well to lopping and are most productive of leaf. About 175 to 200 trees per hectare give the best combination of mulga for drought feeding and grass for normal seasons.

• Tall mulga: 

old trees with bare trunks and leaves only at the top. They are usually most palatable, but are not amenable to lopping. Utilization without destruction is difficult or impossible. They usually produce large amounts of seed (Everist, 1969).

Distribution

Occurs throughout semi-arid Australia in the 300- to 450-mm rainfall zone with a summer dominance but with some useful winter rain, mostly on lateritic red earth soils acid in reaction and very low in available phosphorus, but also on sandy soils overlying such material. It does not grow on soils containing lime and is not tolerant of wet soils. The drainage lines in the mulga scrubs are usually occupied by Eucalyptus spp., notably E. populnea and Acacia cambagei (gidgee). Perry (1970) describes a grove-intergrove vegetational pattern in mulga communities.
It is tolerant of high manganese. Macroptilium lathyroides grown in lateritic red earth from the mulga scrubs at Charleville, western Queensland, Australia, exhibited manganese toxicity symptoms (Cowie and Skerman, 1970). The hardseedness of mulga can be broken by boiling the seed in water for three minutes. Seedlings usually germinate prolifically after about 7.5 to 10.0 cm rain spread over a few days in summer.
The seedlings are very attractive to sheep and to rabbits and should be protected in the regeneration period for five years or more.
For drought feeding, the mulga is pushed over with a bulldozer or lopped. Sheep will utilize 1.4 kg./head/day of leaves and so the area lopped is adjusted to this consumption.
Day-to-day checking of consumption will soon adjust lopping to the correct requirement. Supplements should be offered to the animals on mulga after three months of feeding since it takes flocks of Merino sheep about three months to adjust to and accept supplementary feed. The supplement recommended is bone flour at 28 g per head per day, salt (NaCl) at 10 to 15 percent of the supplement, and molasses at 168 g per head per day.
Umbrella mulga should be lopped to preserve the lateral branches. Retain 250 trees per hectare as seed trees. Fire should be avoided (Everist, 1969).

Links:

Links for the genus:

• The WattleWeb: Acacias from A-Z
• Sustainable livestock production: Indigenous knowledge in utilization of local trees and shrubs in central Tanzania
• Seed treatment and inoculation: Instructions for acacias and other NFT (Nitrogen Fixing Trees)

Main reference

Everist (1969).