Early Detection of Nitrogen Variability in Maize Using Fluorescence

Early detection of N deficiency is essential for in‐season site‐specific N management for practical and physiological reasons. With current proximal sensing techniques based primarily on reflectance, the detection of N variability before V8 maize growth stage (Zea mays L.) is not reliable, mainly due to a low signal‐to‐noise ratio. The objectives of this study were to assess the possibility of detecting N variability in maize before the V8 maize growth stage using fluorescence and to measure the effect of soil background on fluorescence readings. This experiment was conducted in a greenhouse on potted maize plants that were subjected to four nitrogen rates (i.e., 0, 75, 150, and 225 kg ha−1 N equivalent). The Multiplex3 fluorescence sensor was used to measure the N balance index (far‐red fluorescence induced by UV divided by red fluorescence induced by either red, green, or blue light) at every growth stage starting at V4 and ending at V8 maize growth stage. The results obtained in this study indicate that fluorescence sensing detects maize N variability as early as at V5. Fluorescence, as read by active sensor Multiplex3, is not influenced by soil background at the manufacturer's recommended height of measurement. Portable induced fluorescence sensors have great potential for early detection of maize N variability at early growth stages.