Growers in the Boolba group of the Western Farming Systems Project have identified four legumes that show potential for restoring fertility on the red soils of inland southern Queensland — guar bean (a pulse) and leucaena, lablab, and Caatinga stylo pasture legumes.
With a harvest of 1.4 t/ha and no fertiliser or weed control, the guar bean alone was so successful that growers Rod and Val Gardiner of'Kiama' were planning to put in 160 hectares of it in the next season.
"Everybody was searching for a rotation crop and these legumes seem to be what we need to restore the soils to be sustainable, without losing money," says Mrs Gardiner.
"We can now easily expand from a wheat monoculture system."
Growers in the Boolba group have tried other pulses such as chickpea and lupins. However, they suffered because of problems with feral pigs and kangaroos, as well as weed-control problems on the lighter soils. Reportedly pigs and kangaroos don't fancy any of the latest legumes.
At $300/t and with an Italian company that will buy and process as much bean as growers can supply, guar bean is looking like a promising summer crop for northern growers. The bean is used for an industrial glue process.
According to extension agronomist Nick Christodoulou of the Queenslanc Department of Primary Industries, St George, the search for suitable tropical legumes has been hampered by the severity of frosts through most of the winter months.
"Both the leucaena and stylo pastures used in Northern Australia, for example, are generally frost-sensitive, leaving only selected cultivars such as Unica Caatinga stylo and Tarramba leucaena," says Mr Christodoulou.
The trials mainly aimed to assess establishment and vigour, and all four legumes performed well. Even so, Mr Christodoulou's advice to growers is to wait and see if the potentially frost-sensitive Tarramba survives the winters. The Caatinga stylo, sown a year earlier, has survived the winter of 1999 and it produced well in the 1999-2000 summer.
The fourth legume trialed by the group, lablab, has more than proven its value for both grazing and soil nitrogen. In these trials, a grazed Highworth lablab pasture produced an estimated 3 t/ha of dry matter, putting an estimated 45 kg/ha of nitrogen back into the soil.
"A good lablab pasture could return twice that amount of nitrogen if green-manured. This is not a bad result given that some cultivated soils in the area have nitrogen levels as low as 5 kg/ha in the top 0.9 m," says Mr Christodoulou.
The success of lablab and other legumes trialed by the Boolba group has given growers the opportunity to rejuvenate their soils. The longer-term success of the Caatinga stylo would provide a valuable addition to lucerne and annual medics that struggle on lower fertility red soils, and so provide a legume that will grow in buffel grass pastures.
According to Mr Christodoulou, these new legumes provide one new way of achieving sustainable crop production on the red earths of southern inland Queensland.
Contact: Mr Nick Christodoulou 07 4625 3299