Determination of Cotton Nitrogen Status Utilizing a Digital Camera and Imaging Software.

Inadequate or excessive applications of fertilizer N in cotton (Gossypium hirsutum L.) are financially and environmentally costly.  Timely in-season determination of the N nutritional status of cotton can help producers combat these negative effects; however, current methods of N determination 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.  Recent work utilizing an inexpensive digital camera and image processing software to calculate the dark green color index (DGCI) has resulted in successful determination of corn and turf N status (Karcher et al., 2003; Rorie et al., 2011).  The objective of this research was to examine the effectiveness of the DGCI derived from standard digital photographs and image-analysis software to determine the N status of cotton and to compare sensitivities of calculated DGCI from laboratory, field nadir, and field off-nadir photographs to measurements of leaf N concentrations from laboratory and chlorophyll meter determinations.