Why optimal flowering periods? • Autumn rainfall decline (Cai et al. 2012) • At least partly attributable to anthropogenic climate change (Cai et al. 2013) and results in the systems which bring the ‘autumn break’ to SE Australia being less frequent (Pook et al. 2006, 2009) • Sowing dates required for current cultivars to achieve optimal flowering periods coincide with marked rainfall decline which has regionally reduced yield • In addition, > farm size and > extreme spring weather • Farmers need new cultivar x management strategies to stabilise flowering time

1. Optimal flowering periods
Bonnie Flohr| Mallee Sustainable Farming updates, Manangatang
17 February 2016
AGRICULTURE

2. Acknowledgements
CSIRO Agriculture
• James Hunt, John Kirkegaard, Brad Rheinheimer, Tony Swan
ANU
• John Evans
Funding
• GRDC and ANU
2 | Optimal flowering periods| Bonnie Flohr

3. Why optimal flowering periods?
• Autumn rainfall decline (Cai et al. 2012)
• At least partly attributable to anthropogenic climate change (Cai et al.
2013) and results in the systems which bring the ‘autumn break’ to SE
Australia being less frequent (Pook et al. 2006, 2009)
• Sowing dates required for current cultivars to achieve optimal flowering
periods coincide with marked rainfall decline which has regionally
reduced yield
• In addition, > farm size and > extreme spring weather
• Farmers need new cultivar x management strategies to stabilise
flowering time
3 | Optimal flowering periods| Bonnie Flohr

4. Wheat’s optimal flowering period (OFP)
4 |
• Water stress
• Heat stress
• Frost
• Disease
• Inadequate
growth
OFP
• Critical for yield
• A compromise of all
factors
• Highest yields come
with ~5‐10% frost
damage
Optimal flowering periods| Bonnie Flohr

5. • Previously optimal flowering periods have been defined by last
spring frost and first heat event
• Impact of seasonal water supply on optimal flowering period has
been overlooked
• Using APSIM to model yield combines historic weather records
(including water availability), biomass accumulation and
temperature to identify optimal flowering period = novel
approach
Things to consider in optimal flowering periods
5 | Optimal flowering periods| Bonnie Flohr

6. Method
• Key inputs for model
– Year duration (1963‐2013)
– MET file for site (SILO)
– Soil file for site
– Management: TOS (April 1‐ July 15)
– Fertiliser
– Irrigation
– Variety (mid‐fast)
6 | Optimal flowering periods| Bonnie Flohr

7. 7 |
APSIM sites‐ SE Australian wheat belt
Optimal flowering periods| Bonnie Flohr

8. 8 |
Optimal flowering
period =19 August
to 13 September
Optimal flowering periods: Manangatang
Optimal flowering periods| Bonnie Flohr
Optimal flowering
period (95% of
achievable yield) +ve standard deviation
(variation)
‐ve standard deviation
(variation)
15 day rolling mean

9. Optimal flowering period
9 |
9 ‐29 September
Lameroo
Optimal flowering periods| Bonnie Flohr
Waikerie
23‐ 29 August

10. 10 |
OFP is independent of cultivar maturity type
Mid‐ fast spring
Winter
very slow spring
Optimal flowering periods| Bonnie Flohr

11. A trade off… drought, frost and heat
11 |
Flowering
date
Yield
(kg/ha)
Mean peak APSIM 9-Aug 2456
Mean peak frost and
heat reduced 25-Aug 1819
Frost and heat index
interception 8-Sep N/A
Waikerie
Optimal flowering periods| Bonnie Flohr

12. OFP and declining rainfall: Lameroo
12 |
1998‐2013 vs. 1963‐1997
Optimal flowering periods| Bonnie Flohr
25 Aug‐ 8 Sept 4 Sept ‐ 19 Sept

13. • 1. Sowing date
Ways to hit the optimal flowering period
13 |
Reference: NVT, Victorian Winter Crop Summary 2015
Optimal flowering periods| Bonnie Flohr
APSIM sowing date range for peak average yield (OFP)‐
mid‐fast maturity wheat
Location April May
Waikerie > x <
Lameroo > x x <
Manangatang > x <
= problematic is large sowing programs

14. Ways to hit the flowering window
• 2. Genetics x Management
14 |
Early sowing with slow developing cultivars will
not be adopted in the majority of the Australian
wheat belt (WA, SA, Vic) until there is a winter
wheat that is as high yielding as current elite fast
developing spring wheat cultivars e.g. Mace,
Corack
Optimal flowering periods| Bonnie Flohr

15. SA, WA & NW Vic need a fast maturing winter
wheat
15 |
Mace
Vrn‐A1 Vrn‐B1 Vrn‐D1
v a v
Krichauff
Vrn‐A1 Vrn‐B1 Vrn‐D1
b v v
Peake
Vrn‐A1 Vrn‐B1 Vrn‐D1
a v v
X Or
Fast winter wheat
Vrn‐A1 Vrn‐B1 Vrn‐D1
v v v
25% of F2 progeny
Optimal flowering periods| Bonnie Flohr

16. Fast winter wheat: RAC2341
• RAC2341‐ AGT Roseworthy breeding program
– vav x avv
• 70% Mace
• Responds to vernalisation
– Requires cold temperature accumulation to initiate flowering, fast‐spring
wheats have a low requirement
• Fast to develop once vernalised
• 4 x experimental sites in GRDC early sowing project‐ James Hunt
16 | Optimal flowering periods| Bonnie Flohr

17. Flowering time vs. yield ‐ Minnipa
22‐August – 8 September
Optimal flowering periods| Bonnie Flohr

18. Minnipa SA results 2015‐ James Hunt
18 |
Yield (t/ha) Time of sowing
Cultivar 13‐Apr‐15 29‐Apr‐15 13‐May‐15
Wedgetail 2.8 2.5 1.9
Eaglehawk 2.9 2.3 1.8
RAC2341 3.4 3.6 2.7
Cutlass 3.5 3.6 2.9
Trojan 3.3 3.9 3.0
Mace 2.9 3.8 3.2
Very slow spring 2.2 1.7 0.9
Mid winter 2.4 2.0 1.7
Fast winter 2.7 2.6 2.0
Fast spring 2.0 3.0 2.5
P‐value <0.001
LSD (p=0.05) 0.3
Optimal flowering periods| Bonnie Flohr

19. 19
|
RAC2341 sown 13 April @ Minnipa SA
(photo taken 1 Sep 2015‐ James Hunt)
Flowered 26 July
2.9 t/ha
Flowered 3 September
3.4 t/ha
Optimal flowering periods| Bonnie Flohr

20. Temora results 2015
20 |
Grain yield (t/ha) Time of sowing
Cultivar 17‐Apr 27‐Apr 7‐May 15‐May
Wedgetail 4.3 4.1 3.7 3.2
RAC2341 5.5 4.9 4.4 4.3
Gregory 4.7 4.8 3.9 3.8
Condo 4.7 5.8 4.9 4.4
P‐value <0.001
LSD (p=0.05) 0.4
Optimal flowering periods| Bonnie Flohr

21. Temora 2015
21 |
RAC2341 (fast winter), a broad sowing window (17 April‐ 15 May) same flowering date
Optimal flowering periods| Bonnie Flohr
Optimal flowering
period

22. Key points
• Consider spring drought (seasonal water supply) as an important
determinate of the optimal flowering period, along side frost and
heat
• There is less flexibility in time of sowing with fast maturing wheats
to achieve the optimal flowering period than thought, timely
sowing cultivars to your environment is key to achieving optimal
flowering periods and yield
• Varieties that can respond to the environment (e.g. RAC2341) can
hit the optimal flowering period across multiple sowing dates
(=flowering date stability), increasing yield and system flexibility in
a variable climate
22 | Optimal flowering periods| Bonnie Flohr