Stubble retention loses water

Contrary to expectations, stubble retention on sandy soils in Western Australia increases evapo-transpiration and reduces soil water.

In a preliminary study CSIRO Plant Industry's Dr Phil Ward and summer student Dave Zeelenberg found that stubble retained after harvest acted as a wick and dried out sandy soils. Breaking up or removing the stubble however, resulted in lower soil evaporation rates.

This is in contrast to heavier soils found elsewhere in the country where stubble retention helps maintain water in the soil.

The research, done as part of CSIRO Plant Industry's Summer Student Program, adds to growing knowledge about how to manage the unique soils of the sandplain region in Western Australia that produce about 15 per cent of Australian wheat.

Early results suggest up to 20mm more water is lost if stubble is left standing - a significant amount of moisture for the sandplain region where soils can only hold about 70mm of available water. If the following year is dry then this extra water is critical to the new crop.

If the following year is wet, getting rid of excess water is important. Too much water leaches nutrients and raises the ground water table increasing the likelihood of dryland salinity.

Depending on the following year's forecast, farmers can knock their stubble over, for example by grazing or retain it to get the desired result.

CSIRO Plant Industry's Summer Student program is supported by the Australian Pastoral Research Trust.

MORE DETAILS