POTENTIAL FOR HEAT STRESS
DAMAGE FOLLOWING THE
COOL SPRING OF 2003
Paul Brown
Extension Biometeorologist
University of Arizona
TOPICS
•
•
•
•
Spring Weather Review
Heat Stress
History Lesson
Forecast
SPRING TEMPERATURES
(3rd Coolest Since 1987)
Relative To Normal, Deg. F
Yuma Spring Temperatures
Feb. 1 - Jun. 13
3
2
1
0
-1
-2
-3
-4
87
89
88
91
90
93
92
95
94
97
96
Year
99
98
01
00
03
02
VARIABLE
TEMPERATURES
Spring Heat Unit Accumulation
Yuma
Heat Units/Week
120
100
80
Accept.
60
40
20
Feb
Mar
Apr
MONTHLY PATTERNS
(4 Coolest Springs)
Recent Cool Springs
Departure From Normal, Deg. F
Yuma Valley
3
2
1
0
-1
-2
-3
-4
1995
Feb
1998
Mar
1999
Apr
May
2003
Jun
• For Given Planting Date…
– 5 – 7 Days Weeks Late…
• Two Week Planting Delay…
– 10 – 12 Days Behind
DAYS TO PEAK BLOOM
Monsoon
Planting Date
2/1
2/15
3/1
3/15
4/1
0
10
20
Days To Peak Bloom
30
HEAT STRESS
REVIEW
COTTON HEAT STRESS
• Begins When Crop Temperatures Rise
Above 82.4°F (28°C) For Day
– Level 1
• Crop Temperatures 82.4°F – 86°F
– Level 2
• Crop Temperatures > 86°F
CROP TEMPERATURE, DEG. F
TEMPERATURE & HUMIDITY
CREATE HEAT STRESS
92
88
LEVEL 2
84
LEVEL 1
80
76
30
40
50
60
70
DEW POINT TEMPERATURE, DEG. F
104/73F
109/79F
115/84F
QUANTIFYING HEAT
STRESS
• Canopy Temperature Model
– AZMET
• Air Temperature
• Humidity
• Heat Stress Units (HSU)
– Compute Mean Canopy Temperature
– Subtract 82.4°F From Value
– If Negative, HSU=0
HEAT STRESS HISTORY
(During Primary Bloom)
Yuma Valley
Heat Stress Units
1987-2002
160
140
120
100
80
60
40
20
0
87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02
Year, 19xx or 20xx
HEAT STRESS & YIELD
Yield vs Heat Stress
Yuma Co.
1500
Yield, lb/a
1400
1300
1200
1100
1000
900
0
20
40
60 80 100 120 140 160
Heat Stress Units
PROBABILITY OF HEAT
STRESS
Heat Stress Probability
Yuma Co.
% Probability
100
80
60
40
20
0
Jun
Jul
Any Stress
Aug
Level 2
Sep
HEAT STRESS
SEASONAL ACCUMULATION
Heat Stress Accumulation
Yuma Co.
Stress Units
200
150
100
50
0
Jun
Jul
Any Stress
Aug
Level 2
Sep
HEAT STRESS DURING
FLOWERING
HEAT STRESS & FLOWERING
March 1st Planting Date
1000
1400
1800
2200
2600
HEAT UNITS AFTER PLANTING
Heat Stress
Bloom Curve
3000
HEAT STRESS & PLANTING
DATE
PLANTING DATE
Yuma Valley
3/15
1000
1400
1800
2/15
2200
2600
HEAT UNITS AFTER PLANTING
Bloom Curve
3000
COTTON HEAT STRESS
• No Stress
• Crop Temperatures Below 82.4OF
• NO STRESS
• Level 1
• Crop Temperature: 82.4OF - 86OF
• Level 2
• Crop Temperatures: > 86OF
LEVEL 1 STRESS
• REDUCED FRUIT
RETENTION
• Low – Moderate Fruit Loss
• Small Bolls (3-5 Days Post
Bloom)
• SMALLER BOLLS
• Fewer Seeds/Boll
• Increased Number of Motes
• Shorter Boll Fill Period
LEVEL 2 STRESS
• REDUCED FRUIT
RETENTION
– Heavy Fruit Loss
• Starts Within 1-3 Days
• 2nd Drop: 14 days Later
– Malformed Flowers
• REDUCED BOLL SIZE
– Smaller Bolls
– Hooked Beak Bolls
HEAT STRESSED
FLOWERS...
• Don’t Fully Open
– Smaller
• Little/No Pollen Shed
• “Elongated” Stigma
• Poor Pollen & Ovule
Viability
DELAYED REACTION
BOLLS RETAINED/PLANT
(7 Days Of Level 2 Stress)
2
1.5
1
0.5
0
-10
0
10
20
30
DAYS RELATIVE TO TREATMENT INITIATION
CONTROL
7 DAYS
HISTORY
LOOKING BACK AT PAST
COOL SPRINGS
SPRING TEMPERATURES
& YIELDS (1987-Present)
YUMA COUNTY
Lint Yield, lb/a
1400
1350
1300
1250
1200
1150
1100
COOL
WARM
Spring Temperatures
SPRING & SUMMER
ANALYSIS
• Warm Springs…
– Below Normal Heat Stress
– Above Normal Heat Stress
• Cool Springs…
– Below Normal Heat Stress
– Above Normal Heat Stress
SPRING + SUMMER
Spring-Summer Combinations
Occurrences
Yuma County (1987- Present)
8
7
6
5
4
3
2
1
0
Cool/Low
Cool/High Warm/Low Warm/High
Spring Temperatures/Summer Heat Stress
SPRING/SUMMER ANALYSIS
YUMA COUNTY
Lint Yield, lb/a
1400
1350
1300
1250
1200
1150
1100
Cool/High
Warm/Low
Spring Temp./Summer Heat Stress
FORECASTS
SUMMER FORECAST
(Temperature)
Below (14 )
Above (53 )
Normal (33 )
SUMMER FORECAST
(Precipitation)
Below (33.3 )
Above (33.3 )
Normal (33.3 )
HEAT STRESS REPORTS
(http://ag.arizona.edu/azmet)
THE END