A Survey of Fertility Program Responses of Kentucky Dark Fire-Cured Tobacco (Nicotiana tabacum L.) Yield and Quality for Cigars Manufacture in the Benevento Province (Southern Italy)

Abstract

Summary Nitrogen (N) fertilization of Kentucky dark fire-cured tobacco can be used to increase weight of high quality cured leaves for cigar manufacture. We conducted field experiments at 11 different locations in the province of Benevento (Southern Italy) where the following four N treatments were compared: 1) unfertilized control (N0); 2) a site-specific N rate, calculated by a N fertilization plan (NFP) based on physical and chemical soil characteristics, which ranged between 113 and 145 kg N ha−1; 3) 200 kg N ha−1 (rate commonly used by farmers, N200); 4) 100 kg N ha−1 (half of the rate commonly used by farmers, N100). Yields of the following five commercial quality categories of cured leaves were measured: i) wrappers, ii) heavy filler (Fh), iii) light filler (Fl), iv) heavy shredded (Sh) and v) light shredded (Sl). Fh cured products of B1, B4, B6 and B10 locations were analyzed for: total alkaloids, reducing sugars, chlorides, total N (Kjeldahl), ammonium-N (NH4-N), nitrate-N (NO3-N), and tobacco specific nitrosamines (TSNA). Color parameters: Lightness (L), Chroma (C) and Hue (H) were determined on five cured leaves / plot of both Fh and Fl types at B1, B2, B3, B6, B8 and B10. A blind evaluation of cured leaves collected across locations was conducted by a panel test who considered the main basic characteristics of cured leaves (stalk position, leaf structure, texture, etc.). The total yield of cured products increased with fertilization across locations, up to NFP treatment, without any statistically significant increase at N200 treatment. Fertilization increased yield of wrappers at B1 up to NFP treatment (113.5 kg N ha−1), without any significant increase at N200 treatment. Yield of light filler product was positively influenced by fertilization up to the maximum dose only in 5 out of 11 locations. Total alkaloids significantly increased with increasing fertilization up to 100 kg N ha−1 without any significant changes at higher N rate. Fertilization hardly increased L and C of Fl leaves, which appeared light-brown but brilliant-colored. There was a reduction in the H value of Fh products which indicated a darker tone of those leaves with respect to Fl. Increasing N rate affected production costs more than revenues. According to agronomic results, in most locations the best results in terms of net revenues were obtained by NFP treatment. Considering that N rates above the NFP would disqualify growers from the economic aids provided by EU agrienvironmental measures, by economic point of view the NFP treatment would be recommended over the current grower standard (N200).