Researching the effects of lime on pastures

Acid soils continue to be a serious problem in the high rainfall region of south-eastern Australia, causing reduced crop and pasture productivity and contributing to dryland salinity.

A long-term experiment, started in 1992 to provide mixed farmers with a guideline to managing highly acidic soils, is currently funded by Australian Wool Innovation (AWI) Limited.

In autumn 2004, at the start of the third six-year cycle of the MASTER (Managing Acid Soils Through Efficient Rotations) experiment, both perennial and annual pastures were re-established, said Dr Guangdi Li, NSW DPI senior research scientist.

'The perennial pastures were sown to Australian and Holdfast phalaris, Currie cocksfoot, Aurora Lucerne, and Riverina and Goulburn subterranean clover,' Dr Li said.

'The annual pastures were sown to Wimmera annual ryegrass and Riverina and Goulburn subterranean clover.'

He said during the past 14 years, about 7.5 tonnes a hectare of lime was applied on three occasions to maintain pHCa 5.5 (in CaCl2) at 0-10 centimetres soil. The pHCa on the unlimed treatment varied around 4.0 at the same depth.

On the perennial pastures, lime increased the proportions of lucerne, subterranean clover and barley grass, and kept silvergrass at a low proportion and eliminated sorrel, but had no effect on the proportions of phalaris and cocksfoot.

Dr Li said on the annual pastures, a similar trend was found for barley grass and silvergrass, that is, liming increased the proportion of barley grass and decreased the proportion of silvergrass, but had no significant effect on the proportions of ryegrass and subclover.

Dr Li said the survival of lucerne on the limed treatment, although in low proportion, indicated that the subsoil acidity had been gradually ameliorated as lucerne was highly sensitive to low pH and high aluminium.

'The exchangeable aluminium on the limed treatments decreased from 42 per cent to below 10pc during a 14 year period by maintaining pHCa 5.5 at 0-10 centimetres at the MASTER site.

'The higher proportions of subterranean clover and barley grass, and lower proportion of silvergrass and sorrel indicated that the limed pastures, particularly while barley grass was in the vegetative growth stage, provided stock higher quality feed compared with the unlimed pastures,' he said.

AWI is also providing support to a project at Bywong, where the effects of surface-applied lime in a permanent pasture system are being studied.

For further information, please read Primefact 31-38 at www.dpi.nsw.gov.au/aboutus/resources/factsheets/primefacts.

Further information

Contact: Guangdi Li, Wagga Wagga on 61 2 6938 1930.