Upper Threshold Required for Heat Unit Calculations for Cotton Growth in the Far West

T.A. Kerby, L.T. Wilson, and S. Johnson


 
ABSTRACT

Maximum temperatures during much of the growing season in the Far West are above the temperatures resulting in maximum growth under controlled environments. The use of heat unit cotton growth models without upper temperature thresholds results in an overestimation of the favorableness of the growing season and the time required to complete various physiological events. In some cases, temperatures in excess of 38 C may not only not be adding to growth potential, they may also be reducing net energy for growth. Identification and use of an upper temperature threshold would improve prediction of cotton development from standard weather data and would allow for selection of cultural practices that would optimize yields for any given production season. An accurate description of an upper threshold requires data collection over years and must represent a wide range of temperatures. Utilizing a process of calculating an array of upper and lower thresholds then selecting that combination which minimizes the standard error of the mean divided by the mean, indicates the upper temperature threshold may be well below normal ambient air temperatures during the summer and lower temperature thresholds somewhat below that used in several cotton growth models.



Reprinted from 1985 Proceedings: Beltwide Cotton Production Research Conferences pp. 366 - 368
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998