Cover Story
Fine-Tuning PGR Applications Using Growing Degree Days and Base Temperatures By Barry Stewart, Ph.D., Associate Professor, Mississippi State University, and Ethan Flournoy, Assistant Superintendent, Deerfield Golf Club
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very year in my plant science course, we start by talking about some of the factors needed to grow a plant. Sunlight and water are the two at the top of the list. Next someone will mention soil, and it never fails that hydroponics are brought up. The plants can grow in soil or hydroponics as long as the right nutrients are provided along with support so that the plants can present their leaves to the
10 • Mississippi Turfgrass • Summer 2017
sun. Eventually a student thinks of air being needed for CO2 and O2. We then begin to look for that final factor. The one that does not immediately come to mind is the correct temperature. Outside of the winter months, we tend to forget about the profound effect temperature has on plants and their physiology. In the past two years, we have undertaken several experiments at Mississippi
State University to examine the effects of temperature on warm-season grasses, as well as the effect of temperature on plant growth regulator (PGR) response. One of the ways agronomists quantify temperature is by modeling heat accumulation, often termed “growing degree days” or GDDs. The GDD unit is one of the most frequently modeled indicator of heat accumulation. GDDs are used by agriculturalists