Tuesday, November 14, 2006 - 8:30 AM

Biophysical Basis for the Use of Aerial Color Infrared Photography in Determining Nitrogen Requirements in Corn.

Ravi Sripada1, Ronnie Heiniger2, Jeffrey White3, Randy Weisz2, Carl Crozier4, and Alan Meijer5. (1) Building 3702 Curtin Road, North Carolina State Univ Crop Scie, Building 3702, Curtin Road, University Park, NC 16802-3702, (2) North Carolina State Univ, 200 Lakeside Dr, Edenton, NC 27932-2060, (3) Box 7619, North Carolina State University, North Carolina State University, Department of Soil Science, Raleigh, NC 27695-7619, (4) 207 Research Station Road, North Carolina State University, North Carolina State University, Vernon James Research & Extension Ctr., Plymouth, NC 27962, (5) Vernon James Center, 207 Research Station Rd, Plymouth, NC 27962

Very few studies have attempted to understand the bio-physical basis for the use of aerial color infrared (CIR) photography to quantify in-season corn (Zea mays L.) nitrogen (N) requirements. The objectives of this research were to: i) examine the response of corn agronomic parameters (biomass, plant N concentration, and total N uptake) and spectral parameters (near-infrared [NIR], red [R] and green [G]) from CIR measured at the V7 and VT growth stages to changing environments (year), irrigation, and N applications at planting (NPL); and ii) determine the relationships between corn agronomic parameters and spectral parameters that influence the prediction of optimum N rates at growth stages V7 and VT. Research was conducted during the 2000-2003 corn growing seasons in North Carolina under irrigated and non-irrigated conditions with different NPL rates as the main plot factor. Corn agronomic parameters were measured and aerial CIR photographs were obtained at each site at V7 or at VT. Results indicate that NPL significantly influenced corn agronomic parameters measured at V7 and VT. Corn spectral parameters measured at V7 and VT varied with year and NPL. Green and NIR were significantly correlated with biomass and total N uptake. Relative indices using G and NIR were related to plant N concentration. Among the different indices, relative green difference vegetation index (RGDVI) was the best predictor of corn N status (plant N concentration) at V7 and VT. RGDVI showed consistently significant relationships with corn agronomic parameters measured at VT when analyzed across irrigated and non-irrigated experiments.