How to beat waterlogging: Plant lucerne and trees

Rutherglen researchers check tree rows planted in the trial to reduce waterlogging.

Lucerne is showing it can reduce waterlogging in Victorian trials — a result which could profoundly affect land-use in waterlogging-prone cereal-growing areas.

According to Phil Haines of the Rutherglen Research Institute, unused rain contributes to land degradation and to lost crop yield opportunities (estimated at $39 million per year in the Murray Darling-Basin alone).

As well, native vegetation clearance has increased recharge and caused groundwater levels to rise. The end result — frequent waterlogging in many of our soils.

As a countermeasure, Mr Haines and Rutherglen colleagues are trialing high water-use cropping systems in research funded by growers through the GRDC.

"We want to develop improved cropping systems incorporating perennials and to increase the use of rain where it falls," Mr Haines said.

Lucerne ley

The Rutherglen researchers sowed a lucerne ley in 1993 in one of the wettest paddocks at the Institute. The paddock was limed at 2 t/ha to correct soil acidity and assist the lucerne to establish and grow.

The initial results, compared to continuous crop and annual pasture treatments in the same paddock, show that where the lucerne ley was sown there was 30 mm less water in the soil profile at sowing compared to the annual pasture.

"As soil wetted up over winter in 1995 the lucerne ley treatment took about two weeks longer to reach saturation. In other words it delayed waterlogging for two weeks, which could be critical in farm management terms. In a more average winter it might even prevent waterlogging," said Mr Haines.

The waterholding capacity of the soil also improved under the lucerne ley. According to Mr Haines, this is due to the deep-rooted activity of lucerne, causing more soil pores to develop and better soil aggregates. Water is stored rather than being lost in drainage, and this is used over the drier summer-autumn period by the lucerne.

Alley crops

In a further waterlogging trial in the same paddock, lucerne and trees have been planted in rows as part of an alley crop experiment.

The width of the alleys varied between 10, 15 or 25 per cent of the crop area to help researchers determine the most effective width for reducing waterlogging while aiding crop yields.

The trees are local species, including acacias, and apart from their antiwaterlogging attributes, will provide shelterbelts and some nitrogen fixation.

Subprogram 3.16.08 Contact: Mr Phil Haines 060 304 500