In the last few years, the interest in low nicotine cultivars and agronomic practices that could reduce nicotine accumulation in tobacco leaf has increased with the aim to reduce nicotine content in cigarettes and consequently overall smoking addiction. This study aimed to apply a non-destructive photonic sensing method to the proximal detection of the plant nitrogen (N) status at the stage of maximal plant N assimilation, to find any correlation with leaf nicotine content (%) at harvest.

For two consecutive years a varietal test was carried out at the Fattoria Autonoma Tabacchi (FAT - Città di Castello [PG], Italy), comparing standard and new low-nicotine cultivars of Virginia Bright tobacco managed with local best practices (standard N fertilization and topping) and with low-nicotine agronomic practices (reduced N and no topping). The fluorescence sensor provided indices of leaf chlorophyll (CHL), flavonols (FLAV) and nitrogen (Nitrogen Balance Index, NBI = CHL/FLAV), allowing non-destructive comparisons among agronomic practices. The upper sun-exposed side of a single leaf for each plant was measured in the field by a portable fluorescence sensor at the stage of the maximal plant N assimilation, and before harvest.

Significant differences were found among the differently managed varieties for leaf CHL, FLAV and NBI. The in-field NBI index at maximal plant N assimilation was found to be correlated to the leaf nicotine content (%) destructively measured at harvest.

The study indicates the usefulness of integrating a photonic sensing technology in tobacco cultivation to provide additional information in the identification of new appreciable low-nicotine varieties and in the evaluation of the impact of agronomical practices on the resulting leaf nicotine content.