| Current methods of applying nitrogen (N) fertilizer do not treat small scale variability that is known to exist. Variations in corn grain yield can be found from one plant to the next. With knowledge that yield potential can be predicted by-plant, this in turn can be used to adjust fertilizer N rates for individual plants. This study was conducted in 2010 and 2011 to evaluate by-plant sidedress N using plant height and normalized difference vegetation index (NDVI) sensor readings. Treatments included preplant N rates of 0, 45, 90, and 180 kg N ha-1 with 180 kg N ha-1 as a reference strip. Sidedress N was applied as a variable rate on a by-plant basis, uniform rate on a by-plant basis, and uniform rate on the entire row with a non-fertilized check included. By-plant sidedress N applications increased yields when the preplant N rate was optimized. When preplant N rates exceeded the optimum needed for maximum grain yields, no benefits of by-plant N fertilization were observed. |
