Paul Bullock - Agricultural Drought

Agricultural Drought
Paul Bullock
Department of Soil Science
University of Manitoba
DRI
Theme 1 Workshop

Common Drought Indices in Use
Water Supply Indices
• % Normal Precipitation
• SPI
• Deciles
• Surface Water Supply
Index
Soil Moisture Indices
• Palmer Drought
Severity Index
• Crop Moisture Index
Vegetation Indices
• NDVI and others
DRI
Theme 1 Workshop

Agricultural Drought
• How accurately are
agricultural outcomes
(e.g. grain yield, quality
characteristics)
reflected by drought
indices
DRI
Theme 1 Workshop

Agricultural Drought
Correlation of drought indices with winter wheat yield -
Concho County, Colorado River basin
(Narasimhan and Srinivasan 2005 Ag & For Met 133:69)
Month PDSI SPI-1 SPI-3 SPI-6 SPI-9
1 0.61 0.21 0.79 0.42 0.47
2 0.61 0.46 0.65 0.43 0.42
3 0.66 0.66 0.55 0.63 0.47
4 0.65 0.47 0.60 0.78 0.53
5 0.62 0.16 0.53 0.66 0.51
DRI
Theme 1 Workshop

Air temperature
Humidity
Wind speed
Solar radiation
Precipitation
Soil moisture content
2003 - 2006
DRI Evaporation Workshop
Saskatoon 17 May 2007

Drought Indices Calculated
Water Supply Indices
Accumulated Precipitation
Percentage of Normal Precipitation
Standardized Precipitation Index
Water Demand Indices
Reference evapotranspiration as per Hargreaves et al. (1985)
Reference evapotranspiration as per Allen et al. (1998)
Standard evapotranspiration as per Hargreaves et al. (1985)
Standard evapotranspiration as per Allen et al. (1998)
Potential evapotranspiraion as per Raddatz (1993)
Actual evapotranspiration as per Raddatz (1993)
Water Balance Indices
Moisture deficit (Soil moisture at planting + Precip – HarETc)
Moisture deficit (Soil moisture at planting + Precip – PMETc)
Modeled crop water use (using HarETc)
Modeled crop water use (using PMETc)
Moisture deficit (Soil moisture at planting + Precip – PamETp)
Abbreviation
Precip
%Norm
SPI
HarETo
PMETo
HarETc
PMETc
PamETp
PamETa
HarDef
PMDef
HarWU
PMWU
PamDef

Time Periods Considered
• Monthly Periods of Index Accumulation
• May May
• June Jun
• July Jul
• August Aug
• May through June MayJun
• June through July JunJul
• July through August JulAug
• May through July MayJul
• June through August JunAug
• May through August MayAug
• Growing Season Periods of Index Accumulation (for all but %Norm and SPI)
• Vegetative Period (from date of planting to date of anthesis) PlAnth
• Reproductive Period (from date of anthesis to date of maturity) AnthMat
• Growing season PlMat

Drought indices with the highest r for wheat yield and quality (AC Barrie)
Grain Parameter Index Time Period r
Grain Yield PamETa AnthMat 0.87*
PamETp Jul -0.77*
Grain Protein PMETo PlMat 0.89**
Concentration PMETo PlAnth 0.87*
1000 kernel weight PamETa May 0.78*
PamETa AnthMat 0.78*
Flour Protein PMETc JulAug 0.92**
Concentration PMETo PlMat 0.91**
Flour Pentosan PamETa Jun 0.91**
Content PamETa MayJun 0.80*
Farinograph PMETc MayJun 0.89**
Absorption PMWU MayJun 0.89**
Farinograph Dough PMETc PlAnth 0.95**
Development Time HarETc JunAug 0.90**
Farinograph Stability PamETp PlAnth 0.88**
PamETp JunJul 0.87*
Loaf Volume HarETo PlAnth 0.93**
HarETc JulAug 0.89**
* , ** - significant at 5% and 1%, respectively

18
16
Barrie Flour Protein = 0.030 (Jul-Aug PMETc) + 6.74
r 2 = 0.84**
Flour Protein (%)
14
12
10
8
Superb Flour Protein = 0.033 (Jul-Aug PMETc) + 5.62
r 2 = 0.89**
100 150 200 250 300 350 400
Jul-Aug Penman-Monteith Potential ETc (mm)
Jul-Aug PMETc

Drought Index Performance
AC Barrie Superb
• Water Supply Indices 0 1
• Accumulated Precipitation - -
• Percentage of Normal Precipitation - -
• Standardized Precipitation Index - 1
• Water Demand Indices 25 21
• Reference evapotranspiration as per Hargreaves et al. (1985) 1 3
• Reference evapotranspiration as per Allen et al. (1998) 4 2
• Standard evapotranspiration as per Hargreaves et al. (1985) 2 2
• Standard evapotranspiration as per Allen et al. (1998) 8 8
• Potential evapotranspiraion as per Raddatz (1993) 4 2
• Actual evapotranspiration as per Raddatz (1993) 6 4
• Water Balance Indices 2 5
• Moisture deficit (Soil moisture at planting + Precip – HarETc) - -
• Moisture deficit (Soil moisture at planting + Precip – PMETc) - -
• Modeled crop water use (using HarETc) 1 1
• Modeled crop water use (using PMETc) 1 4
• Moisture deficit (Soil moisture at planting + Precip – PamETp) - -

Time Periods Considered
• AC Barrie Superb
• Monthly Periods of Index Accumulation 16 16
• May 2 5
• June 2 -
• July 1 2
• August - 1
• May through June 4 3
• June through July 1 -
• July through August 3 3
• May through July 1 -
• June through August 1 2
• May through August 1 -
• Growing Season Periods of Index Accumulation (for all but %Norm and SPI) 11 11
• Vegetative Period (from date of planting to date of anthesis) 7 4
• Reproductive Period (from date of anthesis to date of maturity) 2 5
• Growing season 2 2

Agricultural Drought
• In the later stages of grain filling,
there is extensive remobilisation
of carbohydrate from storage in
stems and leaves to grains
through the phloem pathway
(Porter and Hay 2006 The
Physiology of Crop Yield).
• Atmospheric moisture demand
dictates water potential in the
plant heads and this may control
the amount of assimilate flow
through the plant at this stage.
photosynthesis
grain growth
Stoy 1980 Physiol. Aspects of Crop Productivity
DRI
Theme 1 Workshop

Agricultural Drought
• Would drought indices
based on ET through key
growth stages quantify
agricultural effects of
drought better than other
indices currently in use
DRI
Theme 1 Workshop

Next Steps
1. Add the 2005 and 2006 results to the drought index
correlation analysis.
3. Estimate 1999-2003 spring wheat yield and grain protein
concentration at each weather station in western Canada
using various indices including ET-based.
5. Assess the yield estimates with small area crop statistics
from Statistics Canada.
7. Assess the grain protein concentration estimates with
Canadian Grain Commission harvest survey data.
DRI
Theme 1 Workshop

Other Potential Information for
the Paper
1. Maps of Statistics Canada crop yield by crop division or
census district across western Canada for 1999-2003.
3. CCAP maps and statistics by census division of NDVI
during peak growth periods for 1999-2003.
DRI
Theme 1 Workshop