Dramatic results from draining WA wheatlands by Guy Cotsell

Two photos of field

Waterlogging in dryland farming sounds like a contradiction, but it has now emerged as the single biggest problem for graingrowers in the wetter western areas of the WA wheatbelt.

Agriculture WA (AgWA) researchers have already found they can increase yields substantially if they can reduce waterlogging. In trials at Mt Barker they achieved increases of 50 per cent by direct drilling barley into raised seed beds. They attribute this increase to the drainage provided by the raised beds combined with the improvement in soil quality resulting from direct drilling.

Project leader Greg Hamilton said that, in addition to the dramatic increase in yield, the drainage furrows between beds provide other bonuses — machinery can traverse the raised bed area during the growing season to apply in-crop weed control, and the roots of new crops can get immediate benefit from the drainable air-providing pores (macropores) created by the previous crop roots because they will be sown in the same rows.

A general costing is $45/ha for bed installation. Other production costs — seeding, weed control and harvesting — remain constant, Mr Hamilton said.

Major GRDC project

Surveys by AgWA and CSIRO suggest that crops in the wetter western areas of the wheatbelt achieve only 40 per cent of their potential yield. The GRDC's Western Regional Panel has set out to remedy this with a major five-year project.

AgWA researchers developed a computer model to study historical rainfall and evaporation records, which confirm that about 80 per cent of the 400+ mm rainfall western agricultural area is likely to suffer waterlogging in June-August. Analysis of conditions at Katanning showed that waterlogging in July-August occurred for seven out of 10 days for the 100 mm topsoil and five out of 10 days for the 300 mm-deep topsoil. Waterlogging on this scale will greatly reduce yield, particularly in crops sown from mid-May onwards.

Two -way attack

The attack on waterlogging is two-pronged — the raised beds drain the water away, and the direct drilling allows the soil to produce sufficient macropores to aerate the soil so that plant roots can function properly.

Although the researchers believe raised beds and no till are the best bet for preventing waterlogging, nobody is claiming it is easy. Some farms have complex landscapes, and farmers have to be able to operate the beds and get rid of the water.

This year researchers are installing an intensively monitored research site and a number of farmer-operated demonstration trials on wheatbelt farms as well as a new site at Esperance Downs Research Station. Work at the Mt Barker site will continue.

Mr Hamilton expects the new trials to confirm the encouraging results already obtained. He compares the substantial promise' of his trials with the Southern Farming Systems experience in Victoria.

"In fact, the promise appears to be great enough to encourage its application to broadacre cropping, even allowing for the cost of installing and maintaining a system of beds and catch drains."

Subprogram 3.5.3 Contact: Mr Greg Hamilton 08 9368 3276

Region North, South, West