DROUGHT
» By Jasia Jannat, PhD, and George Vellidis, PhD
Together, these changes increase evapotranspiration and rapidly lower soil moisture. In sandy soils with low water-holding capacity, flash drought may quickly result in crop water stress and, depending on crop growth stage, significant yield losses to rainfed crops. The U.S. Drought Monitor (
droughtmonitor.unl.edu), which is often used to justify federal assistance for crop damage resulting from drought, may not always identify localized flash droughts.
F
An ongoing study funded by the National Oceanic and Atmospheric Administration that is being conducted by the University of Alabama-Huntsville, the University of Florida and the University of Georgia is developing methods for identifying and quantifying the effect of flash drought with each university focusing on different strategies. UGA is focusing on using a mathematical modeling approach to address this problem.
lash drought is generally understood to be the rapid onset or intensification of relatively short-term agricultural drought. It occurs because of lower- than-normal rates of precipitation accompanied by abnormally high temperatures, winds and solar radiation.
BUILDING A MODEL
Over the past few years, UGA and UF have worked together to develop a suite of smartphone-based irrigation scheduling apps called the SmartIrrigation apps (
smartirrigationapps.org). Among other crops, these apps are available for corn, cotton and soybeans. Apps for peanuts and forages are under development. The apps use weather data to estimate daily crop water use and utilize this information to calculate the amount of plant available water available in the soil profile. They have been extensively tested in southern Georgia and northern Florida and perform as well as soil moisture sensors in scheduling irrigation.
For this project, the cotton, corn and forages SmartIrrigation apps are being used to identify periods when soil moisture becomes dangerously low under rainfed conditions.
In most situations, we irrigate crops when plant available soil moisture drops below 50%. We trigger irrigation at this level to ensure that we have a time buffer in which to apply water before the crops begin to experience water stress. When plant-available soil water drops below 30%, the remaining soil water can be
irrigationtoday.org
Winter 2023 | Irrigation TODAY 11
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