Improving Early Season Detection of Corn Nitrogen Stress Using NDVI.

Reducing nitrogen (N) losses while increasing N use efficiency (NUE) has become the goal of corn (Zea mays) N fertilization (Robertson and Vitousek, 2009). Active remote sensing with the GreenSeeker® sensor has been proven effective at determining N rate prescriptions at the V7 to V9 growth stage (Teal et al., 2006). However different background types can influence NDVI values (Huete et al., 1985). Delaying N application until the V7 stage can result in yield loss to early season deficiencies.  Our objective was to evaluate the effect of sensor orientation, field of view and soil type and soil cover on corn NDVI readings from the V2 to V6 stage.  Five field studies were conducted in 2011 and 2012 in Virginia. Along with GreenSeeker® NDVI readings, destructive tissue analysis, SPAD chlorophyll meter readings and yield data were collected at the V2 to V6 stages. In addition, one experiment was performed to quantify NDVI variation due to background soil color, residue cover, and different sensor orientations.