Submitted to: American Society of Agronomy
Publication Type: Abstract Only
Publication Acceptance Date: September 20, 2008
Publication Date: October 15, 2008
Citation: Russ, A.L., Daughtry, C.S., Meisinger, J.J., Gish, T.J. 2008. Assessing spectral reflectance sensors for detecting N stress corn [abstract]. American Society of Agronomy. 2008 CDROM.
The use of remotely sensed data to direct the variable application of fertilizer for the improvement of nitrogen (N) use efficiency is a subject of great interest to the agronomic community. A new generation of active, multi-spectral remote sensing instruments permits more frequent sampling of crop conditions because they are able to collect reflectance data under a variety of sky conditions. Data collected at this higher temporal frequency allows for issues such as the interaction between plant growth stage and the instruments ability to detect N stress to be more fully investigated. In addition, many field radiometers now have additional spectral bands which allow for the development of new vegetation indices that offer an improvement in the detection of N stress. A multi-year evaluation on the use of remotely sensed data to discern N stress in corn has been conducted at two diverse locations in the state of Maryland between 2004 and 2008. Biophysical data including plant height, leaf area index (LAI), leaf chlorophyll content, development stage, and reflectance were acquired weekly from growth stages V6 to R1. The temporal expression of N stress varied from year-to-year due to residual soil N and prevailing meteorological conditions. The correlation coefficients of the vegetation indices were strongest when the indices were compared with percent cover and LAI at early growth stages. Vegetation indices that incorporated spectral bands within the red edge (720 nm) were found to have higher correlations with leaf chlorophyll than was obtained with indices that did not use the “red edge” bands. The correlations between remotely sensed vegetation indices and leaf chlorophyll content typically increased as the corn matured and N-stress became more pronounced. The most statistically significant correlations between vegetation indices and leaf chlorophyll content were found when the crop reached a growth stage of V8 or beyond.