Key Messages

• Data collected in 2003 and 2004 have been used to update the ' Flowering Calculator ' to predict the flowering time of current wheat varieties grown in a range of locations and sowing times.
• Predictions for key locations and over 16 varieties are available to assist in determining sowing sequences for varieties to maximise yield and minimise frost risk.

Background

The choice of sowing date and variety is the key to maximising yield potential. Earlier sowing should mean better water use efficiencies and higher yields. Successful adoption of this strategy hinges on matching variety to sowing time to maximise growth and minimise the likelihood of frost damage after flowering, yet avoid the incidence of high temperature events and terminal drought during grain fill. The Flowering Calculator is a tool that enables the user to compare flowering dates relative to risks of frost and high temperature events and the likelihood of experiencing optimum conditions during grain development.

The Flowering Calculator provides a procedure to calculate flowering date using average daily temperature and day length.

• The user can interrogate daily temperature data records to provide information on incidence of frost and critical mean temperature events after flowering, high temperature events towards the end of grain filling and variation in flowering time.
• Outcomes for a range of varieties can be assessed relative to user-defined flowering windows and end of season dates, for any date of sowing.
• The user can define frost, critical high temperature events in terms of severity and duration.
• The user can select one or more years of temperature record to calculate year specific flowering times and identify occurrence of frost, critical temperature, and high temperature events in those years.

Parameter data are supplied to enable flowering time to be calculated for a selection of varieties for each of several crop species using a range of phenological models. The models were selected on the basis of : (i) enabling easy generation of parameters as new varieties come to hand using sowing date, flowering date, and daily temperature and site latitude data ; , and (ii) accessing existing and developing parameter data bases.

The model used is as follows :

1/D = a + b(Temp mean) + c(Day length mean)

where : D = the duration from sowing to flowering in days ;

a, b & and c = are coefficients related to basic vegetative period (BVP), temperature
response and photo-period response respectively.

Aims

Flowering data collected by the project "Variety specific agronomy for wheat yield and grain quality in the Western Region - DAW0012" will be used to generate parameters for 'Flowering Calculator' to predict the flowering times for the current wheat varieties grown in a range of locations and sowing times in WA.

Method

Flowering dates (50% anthesis) were observed for twenty current and potential new varieties sown at three sowing dates at Mullewa, Mingenew, Nungarin, Quairading and Katanning in 2003, and Mullewa, Eradu, Northam and Katanning in 2004.

The sum of the mean daily temperature was calculated from sowing to flowering from the closest weather station located near each of the sites. The latitude of the location was used to calculate the mean day length. These values where then used to calculate the regression parameters for each variety.

Results and Conclusion

Table 1: Predicted flowering dates in three regions using the Flowering Calculator

Shaded areas represent the estimated ' flowering window' for the three regions.

From the mid May sowings, the predicted flowering dates closely correspond to actual flowering dates observed in the field. Early May predictions tend to be under estimating the flowering time. Additional information on varieties and regions will be available at the crop updates.

Acknowledgments

We would like to thank Melaine Kupsch, Glenda Smith, Steve Penny and Judith Devenish for their dedication in observing the flowering dates. The financial support of the GRDC, and the support of the Geraldton, Merredin, Avon and Katanning Research Support Units is gratefully acknowledged. Thank you also to Ian Foster and Peter Hansen for providing the weather data

Source: http://www.grdc.com.au/growers/res_upd/west/05/shackley.htm