Determination of Differences in Corn Biomass and Nitrogen Uptake At Various Growth Stages Using Spectral Vegetation Indices.

Application of canopy sensors for nitrogen (N) fertilizer management for corn grain production in the Southeast US requires first the identification of the relationship between field-measured crop status  and sensor-measured canopy spectral reflectance.  A nitrogen test was conducted between 2009 and 2011 at three research stations in Alabama to identify the best vegetation index and corn growth stage to assess differences in biomass and nitrogen uptake from corn receiving various N application rates. Nitrogen treatments included five N rates at 0, 56, 112, 168, 224, 280 kg ha^-1 applied at planting. At each location, data of SPAD, LAI, leaf N tissue, and canopy spectral reflectance were collected at V6, V8, V10 corn growth stages.  A canonical correlation analysis was conducted to identify the vegetation indices best correlating with field-measured crop status variables and the type of relations existing between both groups of variables. Results from this study will be utilized in developing an algorithm for variable rate application of nitrogen in the Alabama.