Nitrogen accumulation, distribution and use efficiency of flue-cured tobacco under different soil texture

【Objectives】 Soil texture generally reflects inherent soil fertility, affectes soil nutrient supply, especially soil nitrogen supply and nitrogen fertilizer utilization in farmlands. In this study, the nitrogen absorption, accumulation and utilization of flue-cured tobacco in different soil texture in south Anhui were studied to provide a scientific basis for localrational fertilization in flue-cured tobacco. 【Methods】 A field experiment was established in loam, clay loam and sandy loam soils in the modern agricultural science park of south Anhui tobacco planting area. The15N field trials combined with laboratory analysis were conducted in this study. The biomass amounts of different parts of flue-cured tobacco were measured after blenching and drying of these samples, which were taken from the field trial with the similar growing trend at the rosette stage (38 days after the transplanting), budding stage (53 days after the transplanting), topping stage (64 days after the transplanting) and maturity stage (103 days after the transplanting) of flue-cured tobacco. The total nitrogen contents of different parts of flue-cured tobacco were measured by the kjeldahl nitrogen determination method, and the abundances of15N were measured by ZHT-O2 mass spectrometer. 【Results】 The total nitrogen contents and fertilizer nitrogen accumulation amounts of tobacco in loam soil and clay loam soil both exhibit a single peak pattern during the growing season, and reach their maximum values at the topping stage, with the total nitrogen 4.25 g/plant and 3.96 g/plant, and the fertilizer nitrogen 2.34 g/plant and 2.54 g/plant, respectively. The total nitrogen content and fertilizer nitrogen accumulation amount of tobacco in sandy loam soil reach their maximum values at the maturity stage, with the total nitrogen 5.64 g/plant and fertilizer nitrogen 2.73 g/plant which are significantly higher than those in loam soil and clay loam soil at the same stage. The ratios of fertilizer nitrogen to total nitrogen and the nitrogen distribution rates of tobacco in three soils are all highest in leaves, followed by stems, and lowest in roots. The change tendencies of nitrogen use efficiencies of tobacco at different developmental stages are similar to those of the fertilizer nitrogen accumulation in the three soils. The maximum values of nitrogen use efficiencies in loam soil and clay loam soil are observed at the topping stage and are 34.5% and 40.7% respectively. And then, the values decrease gradually in loam soil and rapidly in clay loam soil with the developmental stage. The nitrogen utilization efficiency of tobacco in sandy loam soil increases with the developmental stage and reaches the maximum value of 43.7% at the maturity stage. 【Conclusions】 The order of nitrogen absorption and utilization of tobacco in different soils is sandy loam loam clay loam. Due to its weak nitrogen supply capacity, nitrogen mineralization in clay loam soil should be promoted and more nitrogen fertilizer should be applied for growing tobacco. While, less nitrogen fertilizer should be used in sandy loam soil because of its higher nitrogen utilization efficiency.