Assessing residue effects of tobacco nicotine on the yields, nutrient concentrations and nicotine uptake of a subsequent maize crop

The residue effects of tobacco (Nicotiana tabacum L.) nicotine on the subsequent maize (Zea mays L.) crop cultivated in soils differing in texture has rarely been studied for over a decade. The present study was conducted on sandy soil of Tabora, and loamy sand soils of Urambo, and Sikonge sites in Tabora region of Tanzania, to assess the residue effects of tobacco nicotine on latter performance of a maize crop. The experiment was laid out in a complete randomized block design with three replications. During the first cropping season (2017-18), the treatments were composed of one unfertilized cultivated plot of tobacco as a control and a fertilized cultivated plot, where the seedlings of flue-cured tobacco variety K326 were transplanted. Two separate plots were kept fallow for planting sole maize (DKC-8053) under fertilized and unfertilized conditions without any nicotine residue during the succeeding second (2018-19) and third (2019-20) cropping seasons. Moreover, in the first cropping season, in one fertilized tobacco plot, tobacco stalks after reaping leaves were incorporated in soil for natural decomposition, while in the other fertilized tobacco plot, tobacco stalks were uprooted. In the second and third cropping seasons, the residue nicotine was measured in soils and found to range from 0.25 to 0.86 mg kg- 1 in both unfertilized and fertilized tobacco plots. The residue nicotine ranged from 0.92 to 1.05 mg kg- 1 in fertilized tobacco cultivated soils with tobacco stalks. Results showed that nicotine residue in soil decreased maize grain yield by 0.08 t ha- 1. The decrease of maize grain yield was also attributed to inadequate P and K levels in soils planted with tobacco. Therefore, this study recommends the supplemental application of the limiting P and K nutrients when planting maize after tobacco.