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Wheat yields on acidic Wodgil soils

S.J. Carr1, G.S.P. Ritchie1 and W.M. Porter2

1Soil Science and Plant Nutrition, The University of Western Australia, Nedlands, W.A. 6009
Dryland Research Institute, P.O. Box 432, Merredin, W.A. 6415

Wodgil soils with similar pH values (1:5 H20, CaC12) and exchangeable Al (1M KC1) vary in their ability to support wheat growth. The objective of our research is to find a soil test that can identify those soils that contain concentrations of Al in the subsoil that restrict wheat yields.


The grain yield of four varieties of wheat (Triticum aestivum cv. Millewa, Gutha, Aroona and Wilgoyne) was measured and related to the concentration of aluminium [Al] in the soil solution. In 1987, nine sites were selected to provide a range of potential grain yields (less than 500 to over 1500 kg/ha) for the wodgil soil type [Norpa series(1), Um5.22 (2). In 1988, the original nine sites and five additional sites were resown. The experimental sites were located within 150 km of Merredin (31S, 118E) which has a Mediterranean climate and an average annual rainfall of 310 mm. Basal fertilizers (N, P, Cu, Zn and Mo) were applied at rates sufficient to ensure yields were not limited by nutrients. Before crop establishment, soil samples were collected from seven depths (0-5, 5-10, 10-15, 15-25, 25-50, 50-75 and 75-100 cm). The Al concentration [Al] of the soil solution (extracted at field capacity by centrifugation) was measured and related to grain yield.

Results and discussion

The [Al] in soil solution from the 15-25 cm layer was found to be well related to the grain yield of wheat (Table 1). The difference in variation explained by [Al] between 1987 and 1988 is not fully understood, but is thought to be a seasonal effect (the rainfall during spring of 1988 was much greater than 1987).

On the basis of work so far, a critical concentration would be between 20 and 30 M. This concentration of A1 separates the extremely unproductive soils from those capable of producing an economically viable wheat crop.

Table 1. Values of parameters obtained from curvilinear regression and the variation (r2) in grain yield of wheat explained by [Al] in the soil solution from 15-25 cm.

1. Bettenay, E. and Hingston, F.J. (1961). The soils and land use of the Merredin area, Western Australia. CSIRO Aust. Div. Soils, Soils Land Use Ser. No. 41.

2. Northcote, K.H. (1979). A Factual Key for the Recognition of Australian Soils. Rellim Technical Publications, Adelaide, S.A.

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