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