Capacity of optical fluorescence and reflectance sensors to detect nitrogen, biomass and yield of cotton

Abstract

The objective of this study 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. It was used a randomized block design 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 four N rates (0, 45, 90 and 135 kg ha^‑1). Sensor readings with optical sensors for canopy fluorescence and reflectance were taken 120 days after sowing. There were no significant correlations for N‑NO3 ‑ in the petiole with the reflectance sensor indices; however, they were correlated 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.