[Nitrogen uptake and allocation characteristics of flue-cured tobacco in Nanxiong tobacco-planting area of Guangdong Province].

By the method of field in situ culture and 15N isotopic tracer technique, and taking flue-cured tobacco (Nicotiana tobacum) cultivar K326 as test material, a field experiment was conducted in the Nanxiong tobacco-planting area of Guangdong Province to study the characteristics of soil nitrogen (N) mineralization, the patterns of N accumulation and allocation in tobacco plants, and the allocation of plant-absorbed fertilizer N applied in current growth season. In the study area, the amount of soil mineralized N increased with tobacco growth, peaked at 75 days after transplanting, and decreased thereafter. The soil mineralized N at each tobacco growth stage was significantly higher in the control than in the N fertilization treatment. The N accumulation in tobacco plant organs was in the order of leaf > stalk > root. Tobacco plants mainly absorbed fertilizer N at rosette stage and topping stage, and mainly absorbed soil N at mature stage. The absorbed N in tobacco whole growth period was mainly derived from soil N, and the absorbed soil N and its proportion to the total absorbed N increased evidently with extending growth stage and ascending leaf position. The fertilizer N use efficiency per plant and the residual rate and loss rate of applied fertilizer N were 30. 8%, 32. 3% , and 36. 9% , respectively. In the study area, soil N mineralization rate was relatively high, and soil N had greater effects on the quality of upper tobacco leaves. Under the application rate of 150 kg N x hm(-2), the residual amount and loss amount of applied fertilizer N were relatively high.

[Effects of different planting patterns on the senescence characteristics of flue-cured tobacco roots and leaves].

With flue-cured tobacco (Nicotiana tabacum) cultivar K326 as test material, a field experiment was conducted at Nanxiong area of Guangdong Province in 2008 to study the effects of four planting patterns, i.e., single-row ridge + film mulching at early stage, single-row ridge + film mulching at early and late stages, double-row concave ridge + film mulching at early stage, and double-row concave ridge + film mulching at early and late stages, on the senescence characteristics of its roots and leaves, and the economic traits of its leaves. Comparing with other three planting patterns, double-row concave ridge + film Aulching at early and late stages promoted the root growth of test cultivar during its whole growth period, with the root vigor increased significantly. Meanwhile, the leaf chlorophyll content and protective enzymes (SOD and POD) activities were higher, and the MDA content was lower. The leaf yield, output value, average price, and the proportion of superior leaves were also higher. Double-row concave ridge + film mulching at early and late stages alleviated the senescence characteristics of roots and leaves, and improved the economic traits of flue-cured tobacco leaves, being the efficient planting pattern to product high-quality flue-cured tobacco leaves in Nanxiong tobacco-growing area of Guangdong Province.