In the last few years both FDA and WHO have recommended the lowering of nicotine levels in cigarettes to reduce overall addiction. As a consequence, the interest in low nicotine cultivars and agronomic practices that can reduce nicotine accumulation in tobacco leaves has increased, but presently there are still open questions on the results for growers and industry, especially for quality and smoke flavour characteristics. This study aimed to apply a non-destructive photonic sensing method to the proximal detection of nitrogen (N) status at the stage of maximal plant N assimilation, to find any correlation with leaf nicotine content (%) at harvest.

A varietal test was carried out at Fattoria Autonoma Tabacchi (FAT - Città di Castello [PG], Italy), comparing standard and new low-nicotine cultivars of Virginia Bright tobacco (SLV, ITB697, MS K326 LA, K326) managed with local best practices (standard nitrogen fertilization [N] and topping) and with low-nicotine agronomic practices (reduced N [50 kg/ha] 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 the cultivars. 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. In the field, the NBI index at maximal plant N assimilation was shown to be correlated to leaf nicotine content (%) destructively measured at harvest.

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