In-Season Assessment of Cotton N Status from an Inexpensive Digital Camera.

Nitrogen (N) continues to be one of the most expensive inputs in cotton production but temporal and spatial variability in availability of the nutrient continues to result in over and under-applications from standard ‘blanket’ applications.  Several tools have been introduced in the recent past to fine-tune fertilizer N applications.  Unfortunately, many of these devices are expensive and difficult to integrate into a production system.  An alternative in-season N assessment approach which has shown promise is digital image analysis utilizing inexpensive digital cameras which are included in many mobile communication devices (Raper et al., 2012).  Although these devices are passive (rely on sunlight), they have been able to successfully differentiate between a range of fertilizer N-induced N statuses when used in conjunction with a reference board.  Preliminary results indicate, after further validation, this approach could be integrated almost immediately to assess the need for additional N fertilizer.  This approach could increase the sustainability of cotton production by properly matching fertilizer N with crop demand in space and time.  Furthermore, it appears that a similar device could be integrated onto a sprayer or implement to generate a spatial map of N statuses at a density not practical from a handheld device.