DROUGHT


each of the simulated 30 years. Then we ran the model again and did not allow any rain from May 16 to May 30, and so on. Crops are generally most sensitive to water stress during the reproductive phase because water stress during this phase can negatively affect yield potential. In southern Georgia, corn is typically planted in late March, and it is in its reproductive phase from mid-May through the end of June.


Figure 3 shows the percent reduction in yield compared to the 30-year rainfed average if flash drought occurs for the given two-week periods during corn’s reproductive phase. For Tifton, Georgia, the most sensitive two-week period is between June 1 and June 15, during which flash drought in rainfed corn results in yield reductions as high as 60%. This is the predicted average reduction for the 30-year simulation period. Consequently, the timing of flash drought is as important as its duration in determining yield losses.


Figure 4 shows the simulation results for Quincy, Florida, where the 30-year rainfed average corn yield is 125 bushels per acre. Again, the most sensitive period is between June 1 to June 15, during which flash drought in rainfed corn results in yield reductions larger than 40%.


The deliverable of this project is to develop a database showing the expected yield losses from flash drought for corn, cotton and forages in southern Alabama, southern Georgia and northern Florida. Another goal is to use the SmartIrrigation apps as sentinels to warn growers that their crops are experiencing yield-damaging periods of flash drought.


Armed with this information, growers may be able to seek federal assistance for rainfed crop damage resulting from flash drought. The information is also useful for irrigated crop growers to reference flash drought impact. The SmartIrrigation apps are available to all growers at no cost.


Jasia Jannat, PhD, is a graduate research assistant in the department of crop and soil sciences at the University of Georgia.


George Vellidis, PhD, is a professor of crop and soil sciences in the department of crop and soil sciences at the University of Georgia.


irrigationtoday.org Winter 2023 | Irrigation TODAY 13


THE TIMING OF FLASH DROUGHT IS AS IMPORTANT AS ITS DURATION IN DETERMINING YIELD LOSSES.


Yield Response to Simulated Flash Drought 0


–10 –20 –30 –40 –50 –60 –70


No rainfall (05/01-05/15) Figure 3 No rainfall (05/15-06/01) No rainfall (06/01-06/15) Treatments No rainfall (06/15-06/30) Tifton, Georgia


Simulations using precipitation record from 1992-2021


Planting date = 28th March


Mean rainfed yield = 5161 kg/ha


Yield Response to Simulated Flash Drought 0


–10 –20 –30 –40 –50


No rainfall (05/01-05/15) Figure 4 No rainfall (05/15-06/01) No rainfall (06/01-06/15) Treatments No rainfall (06/15-06/30) Quincy, Florida


Simulations using precipitation record from 2003-2021


Planting date = 15th April


Mean rainfed yield = 7854.58 kg/ha


Yield change (%)


Yield change (%)


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