Analysis of aerial photography for nitrogen stress within corn fields

Spatial variability of soil parameters within fields complicates N fertilizer recommendations for corn (Zea mays L.) production. Thus, the ability to identify differences in crop N status within corn fields could lead to efficiencies in N fertilizer application and decreased ground water pollution. In this study, we digitized aerial color photographic transparencies using an eight-bit scheme to generate digital counts for the red, green, and blue primary colors in the photographs at the R5 growth stage and related them to grain yield. Digital count responses were relative to the N treatment in which grain yield plateaued. Experiments were conducted in 1992 and 1993 for four irrigated corn hybrids with five N Fates on a 6-ha held near Shelton, NE. Red and green digital counts relative to those for the high N treatment provided better prediction of yield response than relative blue counts in both years. In 1993, black-and-white photographs taken with a filter centered around 536 mm also predicted yield response to N well (r(2) = 0.93), These findings permit the use of low cost aerial photographs to characterize variability in crop N status throughout entire fields.