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Waterlogging in a 450 mm rainfall zone in South Australia?

E. Braunack-Mayer

South Australian Department of Agriculture, GPO Box 1671, Adelaide SA 5001

Wheat grown at Roseworthy, in the mid-north cereal belt of South Australia, usually goes yellow in winter and starts to green up again in mid-August. Close inspection of the yellow crops reveals early senescence of the lower leaves. The symptoms are similar to those of nitrogen deficiency and appear to be related to the period of winter rainfall. They could be due to waterlogging, although it seems unlikely that this would occur on a regular basis in a region with an annual rainfall of 450 mm.

Recent research

In 1989, to test whether waterlogging occurs and for what periods, tensiometers were installed in a wheat paddock at Roseworthy, just north of Adelaide. They were placed at 30 cm, in the clay subsoil of a red-brown earth and were read at weekly intervals from sowing until early spring, when the soil suction exceeded the limit of their range (0-0.9 bar).

The soil suction was surprisingly low, that is, the soil was wet, and the air filled porosity was at or below 10% for the entire winter period; mid-May to early August (Fig. 1). Below this, air filled porosity root growth would have been stopped or restricted due to a lack of oxygen (1). Because the sub-soil has a low permeability when wet, it is likely that the topsoil was also waterlogged for long periods during winter and that crop growth was restricted until mid- August.


Waterlogging can decrease the grain yields of wheat in Australia by up to 44 percent (1). If the periods of waterlogging observed in 1989 are a regular occurrence in this major soil group in South Australia, then wheat yields may still be well short of their potential.

Figure 1. Sub-soil moisture during the growing season at Roseworthy, SA.


1. Meyer, W.S., Barrs, H.D., Smith, R.C.G., White, N.S., Heritage, A.D. and Short, D.L. 1985. Aust. J. Agric. Res. 36, 171-185.

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