STRATEGIC NITROGEN STATUS DETECTION WITH CANOPY SENSORS IN EARLY CORN A.A.A. Fox and J. J. Varco Real-time optical sensing systems may assist farmers and researchers in defining appropriate fertilizer N application strategies, and will be of most benefit when attuned to early crop development. Due to market competition and variation in global demand, declining per capita acreage necessitates increases in productivity, profitability, and sustainability through a reduction in fertilizer N inputs and increases in N use efficiency. A study was conducted to develop site-specific nutrient management tools for optical assessment of N status in early corn. The effects of widely varying N availability on crop parameters, such as chlorophyll, leaf N concentration, and yield were correlated to selected vegetation indices. Grown under fertilizer treatments of 0, 80, 160, and 240 lb N/acre, applied in a 50/50 split at planting and V6, early corn was monitored with a tractor-mounted and a hand-held spectroradiometer. The field-sensing outputs were compared and correlated to crop parameters, and used to develop a non-destructive algorithm for predicting plant N status and optimal fertilizer N recommendations.