Optimal flowering periods (Renmark MRU) - Bonnie Flohr (CSIRO)

Optimal flowering periodsBonnie Flohr| MSF updates, Renmark 18 February 2016

AGRICULTURE

Acknowledgements

CSIRO Agriculture• James Hunt, John Kirkegaard, Brad Rheinheimer, Tony Swan

ANU• John Evans

Funding• GRDC and ANU

2 | Optimal flowering periods| Bonnie Flohr

PART 1:Defining optimal flowering periods

Optimal flowering periods| Bonnie Flohr3 |

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


Wheat’s optimal flowering period (OFP)

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• 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

• 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


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)


Method

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Applied frost and heat reducing rules;

Frost yield reductionMinimum temperature between 0 and 2°C during Zadoks stage 60‐69 = 10% yield lossMinimum temperature between ‐2 and 0°C during Zadoks stage 60‐75 = 20% yield lossMinimum temperature less than ‐2°C during Zadoks stage 60‐79 = 90% yield loss

Heat yield reductionMaximum temperature between 32 and 34°C during Zadoks stage 60‐79 = 10% yield lossMaximum temperature between 34 and 36°C during Zadoks stage 60‐79 = 20% yield lossMaximum temperature more than 36°C during Zadoks stage 60‐79 = 30% yield loss


(Bell et al., 2015)

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APSIM sites‐ SE Australian wheat belt


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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

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9 ‐29 September

Lameroo


Waikerie

23‐ 29 August

A trade off… drought, frost and heat

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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


PART 2: Ways to hit the

optimal flowering period

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• Trial in Temora, NSW• 4 times of sowing x 20 cultivars of varying maturity

Ways to hit the flowering window


• 1. Sowing date

Ways to hit the optimal flowering period

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Reference: NVT, Victorian Winter Crop Summary 2015


APSIM sowing date range for peak average yield (OFP)‐mid‐fast maturity wheat

Location April MayParuna > x <Lameroo > x x <Waikerie > x <

= problematic is large sowing programs

Ways to hit the flowering window

• 2. Genetics x Management

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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


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

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Mace

Vrn‐A1 Vrn‐B1 Vrn‐D1

v a v

Krichauff


b v v

Peake


a v v

X Or

Fast winter wheat


v v v

25% of F2 progeny


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


Temora results 2015

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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


Temora 2015

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RAC2341 (fast winter), a broad sowing window (17 April‐ 15 May) same flowering date


Optimal flowering period

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


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OFP is independent of cultivar maturity type

Mid‐ fast spring

Wintervery slow spring


Optimal flowering periods (Renmark MRU) - Bonnie Flohr (CSIRO)

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