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Flowering time and yield of wheat in the Victorian Wimmera using a simulation model

G.J. O'Leary1 and D.J. Connor2

1 Animal Research Institute, Department of Agriculture Victoria, Werribee, vic. 3030

2 School of Agriculture and Forestry. University of Melbourne, Parkville. Vic. 3052

A simulation model of the wheat crop was used to evaluate the effect of flowering time on the yield of wheat in the Wimmera region of Victoria. The model comprises three submodels; water balance; accumulation and allocation of biomass and phonological development (1). The timing of emergence, stem extension. booting, anthesis and maturity is determined by the accumulation of thermal and photothermal units. The soil water submodel determines transpiration from which growth is determined as the product of transpiration and transpiration efficiency (TE). TE is determined by the daily evaporative demand. Growth is partitioned to above-ground biomass, roots and grain with senescence starting at the commencement of stem extension. Potential yield is determined from biomass at anthesis. Actual grain yield depends upon growth after anthesis with an allowance for translocation of assimilate present at anthesis.

Methods

A validation of the model against cv. Olympic showed that it is generally robust and can be applied in the Wimmera. The growth of three cultivar types (early. mid and late) were simulated over a range of seasons experienced at Horsham and the resultant yields compared with the date of anthesis for each cultivar type.

Results and Discussion

The optimal flowering time in the Wimmera was shown to be around the end of October and that yields were very sensitive to the date of anthesis in most years. Some advantage was shown for late- or mid-season cultivars if sown early. but early season cultivars can produce high yields although their optimum anthesis date is earlier than the later types. If it is possible, early sowing with late- or mid-season cultivars is likely to yield better than the later sowings of earlier types in good or average seasons. The incorporation of vernalization response to lengthen the vegetative phase may enable higher yields to be achieved, not only in the wetter and colder areas of southern Victoria, but also in the Wimmera.

1. O'Leary, G.J. et al. 1985. Agric. Systems (in press).

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