DROUGHT Example of Flash Drought Identified by Smartirrigation Corn app for rainfed corn in Tifton, Georgia, in 2021 Smartirrigation Corn User:
Jasia.Jannat@uga.edu
Field: Nespal | Planting date: Mar-28-2021 | Lat: 31.47651, Lon: -83.528869 | Weather data source: AEMN – Tifton Crop
Days after
Date
May-20-2021 May-21-2021 May-22-2021 May-23-2021 May-24-2021 May-25-2021 May-26-2021 May-27-2021 May-28-2021 May-29-2021 May-30-2021 May-31-2021 Jun-01-2021 Jun-02-2021 Jun-03-2021 Jun-04-2021 Jun-05-2021 Jun-06-2021 Jun-07-2021 Jun-08-2021
Figure 1
planting (DAP)
53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72
Acc. heat units
(GDD) (50F)
875 896 922 945 970 999
1028 1058 1087 1116 1141 1163 1186 1210 1237 1264 1291 1319 1346 1373
Phenological stage
V9 V9 V9 V9 V9 V9 V9 V9 V9 V9 V9 V9 V9 V9 V9
Tasseling Tasseling Tasseling R1 R1
Evapotran- spiration (ETo) (in.)
0.2143 0.2329 0.2274 0.1954 0.2196 0.2227 0.2242 0.2246 0.2386 0.2488 0.2296 0.2294 0.2441 0.2308 0.2251 0.1454 0.1844 0.179 0.158
0.1601 Crop
coefficient (KC)
1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05 1.05
Evapotran- spiration (ET × Kc) (in.)
0.22502 0.24455 0.23877 0.20517 0.23058 0.23384 0.23541 0.23583 0.25053 0.26124 0.24108 0.24087 0.25631 0.24234 0.23636 0.15267 0.19362 0.18795 0.1659 0.16811
Effective rain (in.)
0 0 0 0 0 0 0 0 0
0.0088 0 0 0 0
0.4412 0.315 0
0.2431 1.5212 0.5488
Water deficit (in.)
1.88
2.1245 2.3633 2.5685 2.7991 3.0329 3.12 3.12 3.12 3.12 3.12 3.12 3.12 3.12 3.12
2.8315 2.7101 2.8981 2.8209 1.4678
Water deficit (%)
60 68 76 82 90 97
100 100 100 100 100 100 100 100 100 91 87 93 90 47
Percentage of
plant available water used
rapidly used by crops, especially in sandy soils, and result in crop water stress. This level is also referred to as a 70% soil water deficit.
DROUGHT EFFECTS
Based on evaluations with a sophisticated crop growth model described below, we defined flash drought as seven or more days during which plant-available soil water, as determined by the apps, is continuously less than 30%. We ran the corn, cotton and forages apps for virtual rainfed fields of each crop at the 42 UF and 88 UGA weather station locations for the past five years and identified periods of flash drought based on our definition.
Figure 1 shows a period of flash drought identified by the corn app for the Tifton, Georgia, weather station virtual field between May 23 and June 7, 2021. During this period, the soil water deficit exceeded 80% for 16 days and reached 100% (no plant-available soil water) for 10 days. Although this condition does not occur every year, it does occur occasionally.
U.S. Drought Monitor 25 May 2021
Drought Conditions (Percentage Area) None D0-D4 D1-D4 D2-D4 D3-D4
D4 Current 01 June 2021
Last Week 05-25-2021
3 Months Ago 03-02-2021
Start of
Calendar Year 12-29-2020
Start of
Water Year 09-29-2020
One Year Ago 06-02-2020
93.23 97.86
99.43 65.78 97.20 97.58 Intensity: None
D0 Abnormally Dry D1 Moderate Drought
D2 Severe Drought D3 Extreme Drought D4 Exceptional Drought
The Drought Monitor focuses on broad-scale conditions. Local conditions may vary. For more information on the Drought Monitor, go to
https://droughtmonitor.unl.edu/About.aspx
Author: Brian Fuchs National Drought Mitigation Center
6.77 2.14
0.57 34.22 2.80 2.42
0.00 0.00
0.00 0.00 0.00 0.00
0.00 0.00
0.00 0.00 0.00 0.00
0.00 0.00
0.00 0.00 0.00 0.00
0.00 0.00
0.00 0.00 0.00 0.00
droughtmonitor.unl.edu Figure 2
ARMED WITH THIS INFORMATION, GROWERS MAY BE ABLE TO SEEK FEDERAL ASSISTANCE FOR RAINFED CROP DAMAGE RESULTING FROM FLASH DROUGHT.
12 Irrigation TODAY | Winter 2023
To assess the effect of this duration of flash drought on crop yield, we used the Decision Support System for Agrotechnology Transfer Ceres-Maize corn simulation model. This is a widely used model that can quantify the crop’s physiological stress as well as predict yields under a variety of growing conditions. In our case, we calibrated the model using experimental data from Tifton and then simulated the growth of a rainfed corn crop for each of the 30 years for which we had data from the Tifton UGA weather station. The predicted average rainfed yield for the 30 years of simulation was 83 bushels per acre.
To simulate the effect of flash drought on yield, we artificially suppressed rain for two-week periods in each of the simulation years. For example, we did not allow any rain for the period of May 1 to May 15 for
irrigationtoday.org
Figure 2 shows that the U.S. Drought Monitor did not recognize the occurrence of drought in Tift County (where Tifton is located) during this period, primarily because the drought monitor is not designed to take into account the crop water use of specific crops.
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