Abstract:

To clarify the decomposition characteristics of tobacco residues returning to field and the effect on the nicotine content in soil and rice plants, pot experiments were used to study the decomposition characteristics of tobacco stems and roots, and the dynamic changes of soil pH, organic matter and nutrients and nicotine. The results showed that: (1) the decomposing rate and nutrient release of tobacco roots and stems were both fast in the early stage and slow in the later stage, the cumulative release rate of each nutrient was nitrogen (N) > phosphorous (P)> potassium (K), the decomposing rate and nutrient release of tobacco roots were both slower than those of tobacco stems; after tobacco residues returning to field for 120 days, the cumulative decomposing rate of tobacco roots and stems was 45.02% and 53.82%, respectively; (2) returning tobacco stems and roots to field could increase the soil organic matter content by 9.35%-39.87%, the soil pH would decrease at the beginning, but increase after 90 days; (3) nicotine was released fast from tobacco residues, after tobacco residues returning to field for 5 days, about 50% of nicotine was released, and the nicotine in the tobacco residues was basically released after 40 days; nicotine from tobacco roots was released faster than that of tobacco stems, after 30 days, the cumulative nicotine release rate of tobacco roots and stems was 96.95% and 94.03%, respectively, and the nicotine content of each treatment soil was 0 μg/g after 90 days; rice plants absorbed trace amount of nicotine in the early stage, but the content of nicotine in the rice plants was 0 μg/g after 20 days. Overall, returning tobacco residues to field could improve soil nutrients, and there will be no nicotine residue in soil and rice plants in the later stage.

Key words: tobacco residues, decomposition rate, NPK nutrient release, paddy soil, soil nutrient, nicotine