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Applying the GYGA spatial framework and protocols to yield gap assessment of Australian
wheat: what did we learn? Zvi Hochman, David Gobbett, Heidi Horan, Javier Navarro Garcia
CSIRO AGRICULTURE
23 September 2015 - 4th Global Yield Gap Atlas Workshop – Addis Ababa, Ethiopia
Why estimate Australia’s wheat yield gaps ?
• Australia produces 12% of the worlds’ exported wheat (2005-2012) (ABARES, 2012)
• National yields (t/ha) have not increased since 1990 (ABARES, 2014)
• GRDC invests over $100 million annually into R&D targeting improvements in farm production
Understanding yield gaps will contribute to prioritising efforts to increase yields
The Australian grain zone is data rich: yield gap can be assessed at high resolution
In the grain zone we have: Land use mapped at 1km2
resolution 259 SLAs with yield data
3,913 weather stations (average distance 17 km) Detailed soils map 434 geo-referenced soils
with ASC identified
Method scaled up from:
Z. Hochman, et al. 2012. Field Crops Research 136: 85-96.
Visualizing yield gaps | David Gobbett
Wheat growing areas
Visualizing yield gaps | David Gobbett
Weather station 20 km buffers
Visualizing yield gaps | David Gobbett
Weather station 20 km buffers
Visualizing yield gaps | David Gobbett
3 major soils per weather station
Station 76025 (Managatang)
Soil order Cropped area
(‘000 ha)
Soil weight for station
Yw Vertosol 48.4 60.5% Calcarosol 26.1 32.6%
Tenosol 5.5 6.9% Sodosol 0.8
100%
Australian wheat yield gap – high resolution results
National average (1996-2012)
Ya (t/ha) 1.73
Yw (t/ha) 3.45
Yg (t/ha) 1.72
Y% (=100*Ya/Yw) 50.3
Exploitable Yield (Ye) (t/ha) 1.03
Average wheat production 1996-2012 (Mt) 21.5
Additional production if Ye achieved (Mt) 12.7
Annual Value @ AUD 250/t (AUD million) 3,184
van Wart et al. 2013
0 5,0002,500
Kilometers
±Wet
High Temp.Seasonality
Low Temp.Seasonality
AridShort crop
Season
Long cropSeason
Implementing the GYGA protocols: Select Agro-Climatic Zones (DCZs)
• we selected six agro-climatic zones (DCZs; van Wart et al., 2013)
DCZ % of Cereals Area
5102 16
5202 6
6002 27
6102 18
6202 5
7102 8
Total 79
Implementing the GYGA protocols: Weather data and reference weather stations (RWS)
• The Australian Bureau of Meteorology (BoM) manages a network of weather stations with daily data
• 22 RWS were selected within the 6 DCZs.
• Buffer Zone Coverage = 50% of winter grain area
• All RWSs had > 20 years daily rainfall data
• Most also had daily temperature and evaporation data
• Radiation was interpolated from BoM reference stations
Implementing the GYGA protocols: Calculations for Ouyen RWS – cereal & SLA areas
Implementing the GYGA protocols: Calculations for Ouyen RWS – soil, cereal & SLA areas
Implementing the GYGA protocols: Calculations for Ouyen RWS – soil characterisation data
Ya, Yw, Yg and Y% per DCZ
Dotted lines indicate state boundaries
Summary of results at DCZs - aggregated to national level
GYGA-ED CZ
Ya (t/ha)
Yw (t/ha)
Yg (t/ha)
Y% Exploitable wheat yield
(Mt)
5102 2.0 4.3 2.3 46% 2.7 5202 2.3 5.0 2.7 47% 1.1 6002 1.5 3.0 1.5 49% 2.9 6102 1.8 4.0 2.2 45% 3.0 6202 2.0 4.7 2.7 43% 1.4 7102 1.5 3.0 1.5 50% 0.9
National 1.7 (22%) 3.7 (25%) 2.0 (32%) 47% (15%) 15.3
A comparison of results of GYGA protocols with the high resolution data rich analysis
GYGA Protocol (mean)
Data Rich Protocol (mean)
Ya (t/ha) 1.73 1.74
Yw (t/ha) 3.72 3.35
Yg (t/ha) 1.99 1.61
Y% (=100*Ya/Yw) 46.6 50.3
The data were uploaded into the Global Yield Gap Atlas (GYGA)
Australian wheat yield gaps in a global context: The Global Yield Gap Atlas (GYGA) Project
Argentina Australia
Ya 2.2 2.0
Yw 5.8 4.5
Yg 3.6 2.5
Y% 38% 44%
To
tal ra
infa
ll (
mm
)
0
50
100
150
200
250
300
Crop season
X Data
0
10
20
30
40
0
50
100
150
200
250
300
J F M A M J J A S O N D
Tm
ax a
nd
Tm
in (º
C)
To
tal E
TC (m
m)
General Pico, Argentina
(35.7º S; 63.8º E)
So
lar r
ad
iati
on
(M
J m
-2 d
-1)
0
10
20
30
40
J F M A M J J A S O N D
Gunnedah, Australia
(31.03º S; 150.3º W)
Tmax
Tmin
Radiation
ETo
Rain
Crop season
Weather comparison between analogous climate zones in Australia and Argentina
Can Australia emulate Argentina in CZ 6202?
1. Continuous wheat 2. Continuous maize 3. Opportunity wheat –maize double cropping (60 mm PAW for each crop) 4. Opportunity wheat –maize double cropping (90 mm PAW for each crop) 5. Wheat-mungbean double cropping 6. Opportunity wheat-mungbean double cropping (60 mm PAW for mungbean)
Candidate Systems:
System Wheat yield and StDev
(t/ha)
Maize yield and StDev
(t/ha)
Mungbean yield and StDev
(t/ha)
Annual average income (AUD)
Income CV
(%)
Gross Margin
(AUD/ha/yr)
1 4.82 (0.65) - - 1204 14 404 2 - 4.76 (2.34) - 1572 49 692 3 4.03 (1.11) 3.76 (2.71) - 2125 39 369 4 4.24 (1.27) 4.58 (2.60) - 2556 37 739 5 4.55 (0.72) - 1.49 (0.47) 2008 20 833 6 4.57 (0.76) - 1.62 (0.29) 2133 14 799
Surprisingly strong correlation between Ya and Yw for 15 year averages of 22 RWSs
Yield Gap is significantly correlated with available rainfall (15 year means of 22 RWSs)
y = 0.0092x - 0.9414R² = 0.6779
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0 100 200 300 400 500
Yie
ld G
ap (M
g/h
a)
Available rainfall
Available rainfall = Growing Season Rainfall + (0.25 X Fallow rainfall)
The yield gap reduced from 1996 to 2010 but Y% was stable and Ya did not increase!
Yw has declined by 41 kg/ha/yr over 50 highest quality weather stations in the wheat zone
Visualizing yield gaps | David Gobbett
0
1000
2000
3000
4000
5000
6000
7000
8000
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
20
14
Yw
(kg/
ha)
ALL STATIONS y = -41.149x + 86263R² = 0.0185
p=0.00003
Negative trend is significant at 0.05 in 13/50 stations. Nil positive trends. Trend is well explained by fall in rainfall and rise in temperature at these stations
Comparison of the impact of soil type (ASC) on Yw in contrasting agro-ecological zones
NSW NorthEast QLD SouthEast
SA Midnorth Lower Yorke Eyre
SA Vic Mallee
WA Eastern
Conclusions 1. Yield Gap assessment using the Global
Yield Gap Atlas protocols is consistent with results calculated from far more detailed data
2. There is much to be learned from data generated in calculating yield gaps
• In country:
– Gaining insights into drivers of yield gaps
– Impact of climate on yield gaps
– Impact of soil type and soil constraints
• Between countries:
– insights into intensification pathways
Visualizing yield gaps | David Gobbett
Visualizing yield gaps | David Gobbett
Visualizing yield gaps | David Gobbett
Visualizing yield gaps | David Gobbett
Visualizing yield gaps | David Gobbett
Visualizing yield gaps | David Gobbett
Weather comparison between analogous climate zones in Australia and Argentina
Month Solar radiation (MJ/m2/day)
Tmax (ºC) Tmin (ºC) Rain (mm) ETo (mm)
AUS ARG AUS ARG AUS ARG AUS ARG AUS ARG
Jan 24.6 26.1 32.3 30.7 19.2 17.0 75.2 114.5 219.8 217.6
Feb 22.4 23.5 31.5 29.7 19.0 15.8 62.5 101.0 186.4 179.7
Mar 20.0 18.0 29.3 27.1 16.7 14.4 39.3 143.7 178.4 164.0
Apr 15.8 13.6 25.1 23.0 13.1 10.1 45.2 67.0 137.0 124.7
May 12.3 9.7 20.8 18.6 9.3 6.4 45.2 32.0 112.5 102.4
June 10.5 7.9 17.2 15.3 6.3 3.6 39.4 16.1 93.0 87.1
July 11.3 8.9 16.2 14.8 5.3 2.5 53.8 22.6 95.7 88.8
Aug 15.0 12.2 18.3 17.6 6.2 4.0 35.0 25.9 113.5 105.9
Sep 19.2 16.6 21.8 20.3 9.0 6.5 43.6 55.9 140.4 128.5
Oct 22.1 20.5 25.5 23.4 12.4 10.2 51.6 89.3 177.6 165.0
Nov 23.4 24.6 28.2 27.0 15.5 13.4 78.3 100.6 193.9 190.6
Dec 24.7 26.4 30.6 29.6 17.5 15.8 89.0 123.0 215.6 215.9
Annual 18.4 17.3 24.7 23.1 12.5 10.0 658 892 1864 1770
Australia can serve as a “laboratory” for testing hypotheses on yield gap assessment
The GYGA protocols are designed to achieve locally credible assessments of yield gaps at a national to sub national scale.
The GYGA protocols are also designed to make the most of limited data typical of developing regions such as sub-Saharan Africa (SSA) and South Asia (SA).
Accommodating both these goals may necessitate compromise. What then is the cost in detail and accuracy?
In this presentation I will outline the methods used, results and lessons learned from our experience with two levels of yield gap assessment for wheat in Australia:
1. Following the GYGA protocols (6 CZs, 22 RWSs x 3 soil types)
2. High resolution analysis (3,913 weather stations in 258 SLAs x 3 soil types)
Results: Annual Actual Yields Aggregated to DCZs
Results: Water Limited Yields simulated with APSIM and aggregated to DCZs
Schematic framework of yield gap assessment @ SLA resolution
Data layer
Weather, Soil
Farmer Grain Production data
(ABS)
Area Cropped (ABS)
Land use Map 1.1 km grid
Simulation
Yw Yield Map (Local Kriging to SLA
scale)
Yield Gap (Yw-Ya) map at SLA resolution
On-ground credibility testing and process improvement
Multiple Site-specific comparisons against
Ya and Yw estimates
Calculation layer
Ground testing layer
Survey, Census, Remote Sensing
NDVI
Farmer Yields (Ya) (t/ha) at SLA scale
Water Limited Yield Geo referenced points Weather stations and
Soil types
Farmer Data
Actual yields: 15 year average values (1996-2010) at SLA resolution
CZ based comparison of results of GYGA protocols with the high resolution data rich analysis
0.00
1.00
2.00
3.00
4.00
5.00
6.00
5102 5202 6002 6102 6202 7102 National
Yie
ld (t
/ha)
Climate Zone
Ya GYGA
Ya DR
Yw GYGA
Yw DR
Yg GYGA
Yg DR
Yg not significantly correlated with variability in available rainfall (15 yr means of 22 RWSs)
y = -0.6589x + 2.1782R² = 0.0021
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0.00 0.10 0.20 0.30 0.40
Yie
ld G
ap (M
g/h
a)
Rainfall CV
Available rainfall = Growing Season Rainfall + (0.25 X Fallow rainfall)
Ground truthing yield gaps using consultant data from 3835 wheat fields
0
10
20
30
40
50
60
70
80
90
100
0 1 2 3 4 5 6 7 8
Pro
bab
ility
of
Exce
eden
ce (
%)
Grain Yield (t/ha)
Ya Yw Yf
Median Yield (t/ha)
Ya 2.3
Yfield 3.0
Yw 4.0
Key points
• The website is being used and enhanced • Wheat analysis recently extended to include 2012
• Canola recently added, potential to include additional crops
• Compare my farm tool provides a focus for consultants and their clients to discuss yield gaps
Visualizing yield gaps | David Gobbett
• The exploitable wheat yield gap in Australia is considerable • Estimated value over $3 billion annually
• Closing the yield gap will enable Australia to contribute to future global food security
