EFFECTIVENESS OF THE DARK GREEN COLOR INDEX IN DETERMINING COTTON NITROGEN STATUS FROM MULTIPLE CAMERA ANGLES
Tyson B. Raper, Derrick M. Oosterhuis, Upton Siddons, Larry C. Purcell, Morteza Mozaffari

Abstract
Timely in-season N determination in cotton (Gossypium hirsutum L.) can help producers combat the negative effects of inadequate or excessive applications of fertilizer N; however, current methods are often time consuming and/or expensive. More instantaneous, accurate methods of determining N status which utilize equipment already in the possession of the producer are needed. The objectives of this research were to examine the effectiveness of dark green color index (DGCI) measurements derived from standard digital photographs taken by an inexpensive digital camera and analyzed with commercially available image-analysis software to determine cotton N status and to compare sensitivities of calculated DGCI from laboratory, field nadir, and field off-nadir photographs to changes in leaf N and chlorophyll meter measurements. Results suggest DGCI measurements calculated from field off-nadir photographs are a practical and inexpensive method of cotton N determination which could possibly replace measurements using chlorophyll meters.

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