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Two tall wheats equal or outyield two semi-dwarfs with late sowing

W. Anderson, W. Smith, M. Seymour and J. Barclay

Department of Agriculture, Baron-Hay Court South Perth W.A. 6151

Semi-dwarf wheats have outyielded tall wheats on average over most of the Australian wheatbelt and have displaced them in all states, albeit more slowly in Western Australia. However, there is some suggestion that the yield advantage of semi-dwarfs may not be evident under more stressful conditions (1) such as those created by late sowing.

Method

The tall cultivars (CV) Gamenya (mid-season) and Gutha (short season) and the semi-dwarfs Aroona (mid-season) and Kulin (short season) were sown in mid-May, early June and mid-June (TS) at ten sites in the central wheatbelt of Western Australia during 1986, 1987 and 1988.

Results and discussion

There was a significant TSx CV interaction (P < 0.05) at seven sites which indicated that the semi-dwarfs greatly outyielded the talls at the earlier sowings but not at the latest sowing (Figure 1). Regressions of CV yield on site mean yield showed that the talls outyielded the semi-dwarfs at yields below about 2 t/ha which equated to TS of mid-June or later.

The yield advantage for the semi-dwarfs at the early sowing was derived from more and larger kernels (22 and 10%). However, at later sowings the tails had more kernels (2%) which were only slightly smaller (6%). The yield advantage of these semi-dwarf wheats may thus be expressed principally in the cooler, wetter conditions created by early sowing.

(1) Evans, L.T. (1987). 'The future development of maize and wheat in the Third World' CIMMYT Mexico, D.F. p. 79-93.

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