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THE EFFECT OF PROMOTING EARLY VIGOUR ON WHEAT YIELDS
UNDER THREE ENVIRONMENTAL REGIMES

D.H.G. Sloane1, T.G. Reeves1, G.K. McDonald2 and G.K. Hollamby1

1Dept. of Agronomy and Farming Systems, University of Adelaide, Roseworthy, SA 5371
2
Dept. of Plant Science, University of Adelaide, Glen Osmond, SA 5064

Early vigour has the potential to increase water use efficiency and yield of wheat in Mediterranean-type climates (1). Greater early ground cover increases light interception and reduces soil evaporation, increasing transpiration at a time of greater effective rainfall.

METHODS

The effect of promoting early vigour on wheat yield was investigated in a replicated split plot experiment located at Roseworthy, SA on a duplex alkaline soil. Treatments consisted of 2 vigour packages: (i) low, (125 plants/m and 20 kg/ha N); and (ii) high, (200 plants/m and 70 kg/ha N), and 2 cultivars, (Machete and Trident); and 3 simulated post anthesis moisture regimes (stressed, rain fed and irrigated). Phosphorous, 22 kg/ha and nitrogen, 20 kg/ha was applied at seeding as di-ammonium phosphate. A further 50 kg/ha N, as urea, was applied to the high vigour package at early tillering. The growing season rainfall was equivalent to 207 mm (stressed), 285 mm (rainfed), 424 mm (irrigated).

RESULTS AND DISCUSSION

Early dry matter production was significantly increased (P<0.05) under the high vigour package in the period 0-8 weeks after seeding. Leaf area index was 45% greater for the high vigour package at the 2.5 leaf stage. There was a vigour package environment interaction on grain yield and grain protein (Fig. 1). Grain protein was significantly reduced (P<0.05) as yield increased for the high vigour package. Increased water use efficiency was achieved under the high vigour package. Importantly there was no yield penalty associated with high sowing and nitrogen rates with a shortened growing season.

REFERENCES

1. Turner, N.C. and Nicolas, M.E. 1987. In: Drought Tolerance in Winter Cereals. (Eds. J.P. Srivastava, E. Porceddu, E. Acevedo and S. Varma) (John Wiley & Sons). pp. 203-215.

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