The objective of this work was to evaluate the potential of using reflectance and fluorescence sensors to assess the levels of N‑NO3‑ in the petiole, plant biomass production and yield of cotton. A randomized complete block design was used in a 3x4 factorial arrangement, with four replicates. Treatments consisted of three cotton varieties (ST‑4288‑B2RF, ST‑4498‑B2RF and DP-164‑B2RF) and of four N rates (0, 45, 90 and 135 kg ha‑1). At 120 days after sowing, readings were done with optical sensors for canopy fluorescence and reflectance. There were no significant correlations for N‑NO3‑ in the petiole with the reflectance sensor indices; however, there was correlation to biomass production (0.39) and yield (0.32 to 0.41). The fluorescence sensor indices were significantly correlated to N‑NO3‑ in the petiole (0.34 to 0.61), biomass production (0.30 to 0.53) and yield (0.34). Compared to the reflectance indices, the fluorescence ones have a greater ability to assess the levels of N‑NO3‑ in the petiole, a similar ability to detect variation of plant biomass, and a lower ability to detect the variation in cotton yield when increasing rates of nitrogen are applied.
Gossypium; precision agriculture; nutritional status; vegetation indices; NDVI; remote sensing
