Submitted to: Agronomy Abstracts
Publication Type: Abstract only
Publication Acceptance Date: 8/1/2004
Publication Date: 11/1/2004
Citation: Hodgen, P.J., Solari, F., Schepers, J.S., Shanahan, J.F., Francis, D.D. 2004. Effects of active sensor position on maize biomass and nitrogen status estimates. Agronomy Abstracts #6108. Interpretive Summary:
Technical Abstract: The use of active sensors (self illuminating) to estimate maize canopy nitrogen status has the potential to generate real-time information for guiding variable rate application of nitrogen fertilizer. The orientation of the sensor to the crop canopy may affect information generated from the sensor. The purpose of the study was to evaluate two different sensor orientations relative to the canopy row (Nadir and 45 degrees off Nadir of row). Experimental treatments consisted of two maize hybrids, four nitrogen rates (0, 50, 140, and 200 kg N ha-1) and two seeding densities (4 and 8 plants m2). Variation in canopy nitrogen status was measured with two different sensors, that measured canopy reflectance in the near infrared (NIR) and red, or NIR and green around the V9 growth stage. Sensor output was represented as either the normalized difference vegetative index (NDVI) or the green normalized difference vegetative index (GNDVI). Sensor readings, total dry matter, leaf chlorophyll content (with chlorophyll meter) were collected from two meter of row within each plot. In order to collect readings from two orientations, sensors were mounted on a cart that allowed the distance from the target (center of canopy of the row) to remain the same. The ability to predict total dry matter and estimates of N uptake were used as a means of determining the best orientation for acquiring sensor readings.