Pastures and rangelands

Atro Macroptilium atropurpureum

Series: Agnote DPI-306 Edition: First edition Last updated:

NOTE: The information in this Agnote must be read in conjunction with Introduction to selecting and using pastures in NSW, which covers information on areas of adaptation, sources of variability, species mixtures, and important issues related to animal health and the conservation of native vegetation.

Pasture type and use	Creeping, twining, climbing and viny tropical perennial legume for grazing. Atro can be used by cattle in the warmer months or left as a standover to help fill late autumn/winter feed gaps.
Area of adaptation	Subtropical North Coast, preferably away from areas that experience heavy frosts.
Min. average annual rainfall	Down to 700 mm on suitable soils, but performs best when rainfall is above 800 mm.
Advantages	Tolerates drier conditions and poorer soils. Can produce seed in both spring and autumn. Easier to establish than either glycine or desmodium. Has resistance/tolerance to root knot nematodes, and is moderately tolerant to amnemus weevil larvae. Atro can be used by cattle in the warmer months, or left as a standover to help fill late autumn/winter feed gaps. Competitive against weeds. Efficient fixation of nitrogen.
Disadvantages	As with most of the viny tropical legumes, it succumbs to continuous heavy grazing.
Soil requirements	Well adapted to a wide range of soil types, from deep fertile soil to hard stony hill soils. It has good tolerance to high aluminium / high manganese acid soils, but needs adequate phosphorus application to do well on the very poor soils. It does not tolerate poor drainage, prolonged flooding, or strongly saline soils and hard-setting high-sodium soils.
Varieties	Siratro - also used as common name for species. Aztec * - a rust-resistant selection. * Denotes that this variety is protected by Plant Breeder�s Rights.
Sowing rates:
- as only species	Not often sown alone, but up to 4 kg/ha if no seedbed preparation.
- in mixtures	1�2 kg/ha
Sowing time	October to January is best, but avoid hot dry summer spells.
Companion species	Usually sown on warm hill sites with other twining tropical legumes (greenleaf desmodium, glycine and axillaris), and grasses such as setaria, green panic and Rhodes grass.
Inoculation	Group M.
Major nutrient deficiencies	Varies with soil type, but phosphorus, sulfur and molybdenum are the most likely nutrients to be required.
Main insect pests	Bean fly can cause losses in seedling stands, but is of little consequence in established stands. It is less affected by amnemus weevil than is glycine and desmodium.
Main diseases	Rust is the most serious disease in Siratro (but a newly released variety Aztec * has rust resistance). Atro is susceptible to halo blight and rhizoctonia, which can sometimes produce some leaf damage. Rhizoctonia violet root rot can kill some plants, but it is not a significant problem.
Management	It should not be grazed too severely, so that there is plenty of vine and some leaf remaining to allow good regrowth. The more leaf left on the plant, the faster the regrowth. Aim to retain at least a 15 cm height of material to achieve maximum production and persistence. Maintaining reasonable soil phosphorus levels and allowing a good seedset every few years should also improve persistence.
Livestock disorders of particular note	No problems reported.
Additional tips	The best establishment is achieved in well-prepared, weed-free seedbeds. However, atro seedlings are vigorous and, under the right conditions, can be established by broadcasting onto uncultivated pasture, e.g. after burning in natural grass sward that is open, with some bare soil.
Further information	Agfact P2.5.34 Siratro. �Siratro�, Queensland Agricultural Journal (Jan./Feb. 1985), Queensland Department of Primary Industries (DG Cameron).

Acknowledgment

Advice on livestock health disorders was provided by Dr Chris Bourke, Principal Research Scientist, NSW Agriculture, Orange. His contribution is gratefully acknowledged.

Photo: Bede Clarke, NSW Agriculture, Casino