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 SEAustralia 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| MSF updates, Renmark
18 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. PART 1:
Defining optimal
flowering periods
Optimal flowering periods| Bonnie Flohr3 |

4. 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
4 | Optimal flowering periods| Bonnie Flohr

5. Wheat’s optimal flowering period (OFP)
5 |
• 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

6. • 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 availablity), biomass accumulation and
temperature to identify optimal flowering period = novel
approach
Things to consider in optimal flowering periods
6 | Optimal flowering periods| Bonnie Flohr

7. 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)
7 | Optimal flowering periods| Bonnie Flohr

8. Method
8 |
Applied frost and heat reducing rules;
Frost yield reduction
Minimum temperature between 0 and 2°C during Zadoks stage 60‐69 = 10%
yield loss
Minimum temperature between ‐2 and 0°C during Zadoks stage 60‐75 = 20%
yield loss
Minimum temperature less than ‐2°C during Zadoks stage 60‐79 = 90% yield
loss
Heat yield reduction
Maximum temperature between 32 and 34°C during Zadoks stage 60‐79 = 10%
yield loss
Maximum temperature between 34 and 36°C during Zadoks stage 60‐79 = 20%
yield loss
Maximum temperature more than 36°C during Zadoks stage 60‐79 = 30% yield
loss
Optimal flowering periods| Bonnie Flohr
(Bell et al., 2015)

9. 9 |
APSIM sites‐ SE Australian wheat belt
Optimal flowering periods| Bonnie Flohr

10. 10 |
Optimal flowering
period =25 August
to 3 September
Optimal flowering periods
15 day rolling mean
+ve standard deviation
(variation)
‐ve standard deviation
(variation)
Optimal flowering
period (95% of
achievable yield)
Optimal flowering periods| Bonnie Flohr

11. Optimal flowering periods
11 |
9 ‐29 September
Lameroo
Optimal flowering periods| Bonnie Flohr
Waikerie
23‐ 29 August

12. A trade off… drought, frost and heat
12 |
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

13. PART 2:
Ways to hit the
optimal flowering
period
13 |

14. • Trial in Temora, NSW
• 4 times of sowing x 20 cultivars of varying maturity
Ways to hit the flowering window
14 | Optimal flowering periods| Bonnie Flohr

15. • 1. Sowing date
Ways to hit the optimal flowering period
15 |
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
Paruna > x <
Lameroo > x x <
Waikerie > x <
= problematic is large sowing programs

16. Ways to hit the flowering window
• 2. Genetics x Management
16 |
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

17. SA, WA & NW Vic need a fast maturing winter
wheat
17 |
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

18. 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 very low requirement
• Fast to develop once vernalised
• 4 x experimental sites in GRDC early sowing project‐ James Hunt
• Temora
18 | Optimal flowering periods| Bonnie Flohr

19. Temora results 2015
19 |
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

20. Temora 2015
20 |
RAC2341 (fast winter), a broad sowing window (17 April‐ 15 May) same flowering date
Optimal flowering periods| Bonnie Flohr
Optimal flowering
period

21. 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
21 | Optimal flowering periods| Bonnie Flohr

22. 22 |
OFP is independent of cultivar maturity type
Mid‐ fast spring
Winter
very slow spring
Optimal flowering periods| Bonnie Flohr