Theses and Dissertations

Issuing Body

Mississippi State University


Varco, Jac J.

Committee Member

Cox, Michael S.

Committee Member

Reddy, K. Raja

Committee Member

Roberts, Darrin F.

Committee Member

Lawrence, Gary W.

Date of Degree


Document Type

Graduate Thesis - Open Access



Degree Name

Master of Science (M.S.)


College of Agriculture and Life Sciences


Department of Plant and Soil Sciences


Cotton (Gossypium hirsutum L.) reflectance has potential to drive variable rate N (VRN) applications, but more precise definitions of relationships between sensor-observed reflectance, plant height, and N status are necessary. The objectives of this study were to define effectiveness and relationships between three commercially available sensors, and examine relationships of wavelengths and indices obtained by a spectrometer to plant height and N status. Field trials were conducted during 2008-2010 growing seasons at Mississippi State, MS. Fertilizer N rates ranged from 0-135 kg N ha-1 to establish growth differences. Sensor effects were significant, but sensors monitoring Normalized Difference Vegetation Index (NDVI) failed to correlate well with early-season N status. Wavelengths and indices utilizing the red-edge correlated most strongly with N status. Both Guyot’s Red Edge Index (REI) and Canopy Chlorophyll Content Index (I) correlated consistently with N status independent of biomass status early enough in the growing season to drive VRN.