Aerial photography to detect nitrogen stress in corn

Economic and environmental benefits can result from improved nitrogen (N) management in corn (Zea mays L.) production. This research project was conducted to determine the utility of aerial photographs to detect N deficiency in a crop canopy caused by natural soil variability and variable fertilizer N application rates. Chlorophyll meter readings and digitized aerial photograph data were compared to corn grain yield and stalk nitrate concentrations from a 60-ha field in Central Nebraska. In addition to natural field variability, 30.4-m long treatments were imposed through the center of the field by applying fertilizer at: rates of 0, 56, 112, 168, and 224 kg N ha(-1). Grain yield, chlorophyll meter readings,;photographic brightness and stalk nitrate samples were collected. Despite a significant effect from fertilizer treatments, chlorophyll meter readings did not correlate well with grain yields. The brightness of the red component in a digitized color photograph showed a significant inverse relationship (r(2) = 0.42) with grain yield. Stalk nitrate concentrations at harvest, when compared to red brightness from the digitized photograph, provided a better confirmation of N status than grain yield. Aerial photographs appear to be capable of detecting management induced variability as well as reduced yield portions of a field that result from natural variability.