Mexican stand-off with Aztec Atro
From the April 2008 edition of Agriculture Today.
Prudential cattleman Ray Crompton, "Bruton" Casino, is one of the rare farmers determined to master the management of the twining tropical legume Atro.
Atro cultivar Siratro, released in 1971, has been the most successful trailing and twining tropical legume introduced to the NSW Northern Rivers.
This is no great compliment.
Since the late 1960s, dairy farmers and beef producers soon realised that unless strict management practices were imposed, these types of legumes failed to persist.
By 1980 few farmers bothered to establish viny perennial tropical legumes.
Destruction of growing points by repeated hard grazing, leaving insufficient aftermath leaf for plant recovery led to the demise of the "jungle vines".
Atro plants have a half-life of around 24 months.
If no flowering, seeding or plant recruitment occurs within four years following establishment, scant Atro plants will be present in pastures.
Even with judicious management, Atro pastures loose vigour and frequency after five to seven years.
Ray Crompton direct drilled Aztec Atro in March 2006 to rejuvenate a run-down Callide rhodes pasture.
"The fact that Atro doesn’t drop its leaf digestibility and protein with maturity was a compelling feature," explained Ray.
"In spring 2006 Aztec produced a light seeding and a heavy seeding in autumn 2007."
Aztec Atro (released 1994) was chosen over Siratro because of its rust resistance and superior leafiness.
Ray’s Aztec Atro pasture is rotationally grazed.
Under good growing conditions a minimum four week rest period should be imposed.
Four to five weeks is ideal but eight weeks is too long.
When left to bulk-up for long periods the lower leaves are shaded, they defoliate and the root system loses vigour.
Following a grazing, five to 10 tri-foliate leaves are left per stolon.
In an experiment, plants died after three grazing cycles when less than five residual leaves were left per stolon.
To ensure future plant recruitment a seeding should occur soon after establishment and every few years thereafter.
When Atro pastures decline in vigour after five years or so, a spring renovation using widely spaced chisel points stimulates seedling establishment.
Forty years ago the viny tropical legumes found a niche above the frost line on coastal hill country as a standover late autumn/winter supplement.
When dormant in winter, plants can be grazed hard without jeopardizing future production or persistence.
Some of the less showy reject legumes tested during the "sub-tropical pasture revolution" have shown over time to be easier to manage and more persistent than the viny earlier releases.
Sub-tropical perennial legumes for the future are Amarillo and Bolton Pinto forage peanut, Rhizoma peanut and Shaw creeping vigna.
Contact Bede Clarke, Casino, (02) 6662 2288.
