Sensores de reflectância e fluorescência na avaliação de teores de nitrogênio, produção de biomassa e produtividade do algodoeiro

Abstract

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 3×4 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.