烟草残茬还田腐解特征及对土壤养分与烟碱的影响

为明确烟草残茬还田的腐解特征及对土壤和水稻中烟碱含量的影响,采用模拟试验,研究了烟茎和烟根还田后的腐解特征,以及土壤pH、有机质、养分、烟碱的动态变化。结果表明：（1）烟根和烟茎的腐解速率及养分的释放均表现为前期快后期慢,各养分累积释放率依次为钾>磷>氮。烟根的腐解速率及养分释放慢于烟茎,还田120天,烟根累积腐解率为45.02%,烟茎为53.82%。（2）烟茎和烟根还田能提高土壤有机质含量9.35%~39.87%,前期会导致土壤pH降低,但90天后会提高土壤pH。（3）烟草残茬的烟碱释放快,还田后的前5天,烟碱释放约50%,40天后,烟草残茬中烟碱基本释放完毕。烟根的烟碱释放要快于烟茎,还田后30天,烟根的烟碱累计释放率为96.95%,烟茎的烟碱累计释放率为94.03%。至第90天各处理土壤的烟碱含量为0 μg/g。水稻植株在前期会吸收微量的烟碱,至还田20天后,水稻植株中烟碱含量为0 μg/g。综合而言,烟草残茬还田能提高土壤养分,且还田后期土壤与水稻中不会有烟碱残留。

Tobacco Residues Returning to Field: Decomposition Characteristics and Effects on Soil Nutrients and Nicotine

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.