Persistent legumes in North
From the October 2007 edition of Agriculture Today.
Persistent well adapted legumes are a vital part of a productive pasture, according to NSW Department of Primary Industries (DPI) district agronomist at Kyogle, Kerry Moore.
They are vital because the rhizobia bacteria, which live in the root nodules on legume plants, have the unique ability to use atmospheric nitrogen and make it available to their legume host.
This allows legumes to thrive without nitrogen fertiliser inputs, provided they have adequate supplies of other nutrients.
Mr Moore said healthy persistent legumes in a pasture produced a two fold benefit.
They increased the quality of the forage and gradually built up levels of soil nitrogen.
"In turn, better quality forage promotes better animal performance, and more soil nitrogen promotes better grass growth and increases pasture yield," he said.
Graziers wanting persistent legumes also need to impose a regime of management that enables the legume to hold its own against competition from vigorous grasses or weeds.
Amarillo forage peanut has proved to be the most persistent summer growing legume for the Northern Rivers.
"It remains as good as ever on the McAnelly farm at Bexhill after being established 23 years ago.
It has thrived there in a pasture with kikuyu and paspalum that has been given little fertiliser," Mr Moore said.
It tolerates heavy grazing and does best if grass is grazed down fairly frequently - not allowing it to get too tall and shade the peanut.
Amarillo does best in the higher rainfall areas, even though its deep root system allows it to survive severe drought.
However, it needs high humidity and adequate soil moisture to make good growth.
Light frosts burn off the leaves but heavy frosts can kill off stolons.
In situations where its stolons are killed by frost, Amarillo re-establishes from below ground stem and from seed.
Amarillo pegs down all its seed about five centimetres or more into the soil.
On the North Coast it is not recommended for the cooler, more elevated locations or the drier sites under about 1000 millimetres annual rain.
It is adapted to a wide range of soil types, but is not recommended for poorly structured clay soils subject to long periods of waterlogging.
At a recommended sowing rate of 10 kilograms per hectare or more, and about $30 per kilogram for seed, Amarillo is expensive to establish.
It can also be slow to achieve good coverage in a pasture, but once there, it's got real staying power.
Shaw creeping vigna is one of our best legumes for higher rainfall warmer sites, but unfortunately there has been little or no seed available during the last couple of years.
In lieu of creeping vigna, other legumes that could be substituted include Cardillo centro and Villomix villose jointvetch.
"The important thing is that they are legumes and if they grow well, there is a build up of soil nitrogen and an eventual boost to the grass," Mr Moore said.
To obtain more information on establishing and managing pasture species adapted to your area, please contact your local NSW DPI district agronomist.
Contact Kerry Moore, Kyogle, (02) 6632 1900
