Heat Unit Use and Refinement in U.S. Cotton

October 2024 | 29 min., 13 sec.
by Tyson Raper
University of Tennessee

Summary

Thermal time, or growing degree days, have been used for years in agriculture to predict crop growth stages and guide management decisions. This presentation briefly covers the history of degree days in cotton, describes some of the issues in relying on heat units to predict growth stage and guide management decisions, and explains a Beltwide effort to re-evaluate the use of heat units in U.S. cotton production. The base of 60F (which has been used in cotton production since the 1980s) still appears to be one of the simplest approaches for calculating heat units, but the number of heat units required to reach each key growth stage has changed. While it generally takes more heat units to reach emergence, squaring, flowering, cutout, and cracked boll now than previously published, the crop generally moves more quickly from cracked boll to 60% open than previously published. (Additional information is available in this open access Agronomy Journal article).

About the Presenter

Tyson Raper Tyson Raper is the Pettigrew Cotton Specialist for the University of Tennessee, with a 75% Extension and 25% research appointment in the Department of Plant Sciences. Dr. Raper is stationed at the West Tennessee Research and Education Center and leads the cotton and small grains programs. His research and Extension program is focused on variety testing, fertility, and a variety of precision ag projects. Additionally, Dr. Raper manages the University of Tennessee Cotton MicroGin. Dr. Raper received his BS from Auburn University, his MS from Mississippi State University, and his PhD from the University of Arkansas.

Contact Information:
Email: traper@utk.edu

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