Calculation of the Length of Day¹

Abstract

Abstract With the advent of sophisticated computing capability many tables and curves that were standard methods of obtaining values in the past can be computed directly with the appropriate formulas. The photosensitivity of many agronomic crops makes knowing the length of hours that the light intensity is above a certain critical level useful. A formula for calculating daylength is presented and methods indicated for obtaining the desired beginning and ending light intensity at any location. The only information necessary to utilize the formula is the latitude of the location and the critical light intensity of interest for the particular crop being used.