Deep-rooted lucerne alternatives

By Eammon Conaghan

For years, mathematicians have confronted Australian graingrowers with gloomy figures about encroaching salinity.

Well, here is another one. Hydrologists predict that up to one third of arable land in WA will become saline if annual crops are not substantially replaced by deep rooted perennial species which more effectively dry the soil profile.

Many growers have already embraced the message, with lucerne now planted across 150,000 hectares in WA. Other growers are frustratingly short of options because lucerne struggles on acidic and waterlogged soils.

However, GRDC-supported Department of Agriculture researcher, Geoff Moore, says efforts to develop new herbaceous perennial pastures are now well advanced.

“Several promising perennial legume species have emerged in WA trials, including canary clover (Dorycnium rectum), hairy canary clover (D. hirsutum), sulla (Hedysarum coronarium) and perennial Lotus species (L. creticus, L. cytisoides, L. glaber, L. corniculatus and L. uliginosus).”

These species are also being evaluated at a range of other sites across southern Australia through the CRC for Plant-based Management of Dryland Salinity. In WA, they were assessed for their persistence during the dry summer of 2002-03 and for their seasonal production compared with lucerne.

“We’re also investigating the livestock interaction, with optimum grazing strategies being determined for key species of canary clovers at the Medina Research Station in collaboration with Lindsay Bell (PhD student),” Mr Moore says.

“Their feed quality is also under review to examine the effect of the tannins they contain, which are beneficial at low levels but can reduce feed intake and animal production at levels above 10 percent.”

The majority of annual legumes used in Australian agriculture originate from the Mediterranean basin, which is characterised by neutral to alkaline, medium to fine-textured soils. In a bid to broaden Australia’s germplasm, the GRDC has supported seed and rhizobia collecting missions to regions with acidic soils, such as Turkmenistan. Ranging across its harsh, dry environment under a beating 45C sun, researchers collected more than 65 perennial legume accessions of 22 species.

They also collected samples of the soil beneath the plants to isolate the rhizobia bacteria for root nodulation. The effective nodulation of legume roots is integral to plant survival and for fixing atmospheric nitrogen into soils for enhanced production in subsequent cereal crops.

The rhizobia for 15 priority species were developed into inoculants at the Centre for Rhizobium Studies at Murdoch University so that Australian field work could begin quickly.

This diverse germplasm is being fed into the trial program. Although the Turkmenistan material is yet to be evaluated, more advanced species should be released by 2006.

The GRDC is also supporting a major project with the CRC for Plant Based Management of Dryland Salinity to obtain profitable alternatives to lucerne for improved water use.

For more information:
Geoff Moore, DAWA, 08 9368 3293, gmoore@agric.wa.gov.au

GRDC RESEARCH CODE UWA337, program 4