湖南张家界典型植烟土壤地球化学特征研究

Geochemical characteristics of typical tobacco-planting soils inZhangjiajie mountainous area

  • 摘要: 为了研究张家界山地植烟区域土壤的成土环境及地球化学元素的丰缺状况和迁移富集规律, 为烟区优质特色烟叶的生产和布局提供科学依据, 本文采集23个长期耕种的典型植烟土壤剖面样品, 测定分析了25种地球化学元素(氧化物)的含量, 并对土壤的风化发育状况和元素(氧化物)的迁移富集特征进行了研究。结果表明, 张家界烟区主要成土母质如石灰岩、板页岩、紫色砂页岩风化物均受到了较强的风化作用, 化学风化指数(CIA)介于73.19~88.03之间, 总体上土壤具有Ca、Na贫乏而Fe、Al相对富集的化学组成特征。其中紫色砂页岩风化物发育形成的紫色土的风化作用较强, 土壤的淋溶作用较强; 石灰岩风化物发育形成的土壤富铝化程度较低。黄壤、水稻土、紫色土中地球化学元素多数表现出一定的富集特征, 大量有益营养元素的富集对于提高烟叶产量具有重要作用。土壤剖面淋溶层中元素(氧化物)P、B、Se、Mn、Zn、Cu、Ni、Y、Sc、La、Fe2O3、SiO2的含量均高于中国或世界土壤元素(氧化物)中值(均值), 而N、S、Cl、Mo、Co、Sr、Br、I、CaO、MgO、K2O、Na2O、Al2O3的含量偏低, 其中元素(氧化物)N、P、S、Mo、Se、Mn、Zn、Br、I、CaO、MgO在土壤剖面中的含量变化较大。通过对元素(氧化物)富集系数的聚类分析, 将元素(氧化物)分为3类: 呈较强富集特征的元素N、P、S、Se; 呈较强迁移特征的元素(氧化物)Br、I、Mn、CaO; 变化较稳定的其他元素。微量元素B、Zn、Cu和稀土元素Y、Sc、La含量较丰富且变化相对稳定, 表明除了常量元素N、P、S以外, 微量元素Se、B、Zn、Cu和稀土元素Y、Sc、La可能是影响张家界烟区烤烟品质的重要特征元素。

     

    Abstract: Tobacco-planting mountain region have ecological effects on tobacco quality in central south China. The climate, topography, geomorphology, soil parent materials and soil nutrient status are highly heterogeneous factors in the area. Different parent materials and soil types have different degrees of weathering which result in diverse composition and content of soil geochemical elements. The interconnected factors consequently influence the growth and quality of tobacco in mountain regions. Zhangjiajie is a typical mountain tobacco-planting region in Hunan Province of central south China where high quality tobacco is produced. To lay the scientific basis for high quality tobacco cultivation and production, the effects of soil weathering, the abundance or deficiency of nutrients and the migration or enrichment of geochemical elements on Zhangjiajie mountain tobacco cultivation region were investigated. A total of 23 typical soil profiles were sampled and analyzed for 25 types of geochemical elements (or their oxides). The results showed that limestone, plate-shale and purple-sandstone efflorescence of soil parent materials in the region were strongly weathered. The chemical weathering index (CIA) of the soil parent materials were in the range of 73.19~88.03. The soils were characterized by both the depletion of Ca and Na and enrichment of Fe and Al elements. Purple soils developed from purple-sandstone efflorescence showed strongly weathering and eluviation properties. Some of soil types developed from limestone efflorescence exhibited a lower degree of allitization. Most of the geochemical elements of yellow soil, paddy soil and purple soil were highly enriched which was critical for tobacco yield. There were higher contents of P, B, Se, Mn, Zn, Cu, Ni, Y, Sc, La, Fe2O3 and SiO2 in the eluvial soil horizon, higher than the median of these soil elements in China or in the world. However, the contents of N, S, Cl, Mo, Co, Sr, Br, I, CaO, MgO, K2O, Na2O and Al2O3 in the eluvial soil horizon were low. Both the macro elements of N, P, S, CaO and MgO and the trace elements of Mo, Se, Mn, Zn, Br and I significantly changed along the soil profile. The hierarchical cluster analysis method was used to classify the enrichment coefficient of geochemical elements into three groups. The groups consisted of N, P, S and Se with strong enrichment characteristics; Br, I, Mn and CaO with strong migration characteristics; and then the relatively stable elements. B, Zn and Cu trace elements and Y, Sc and La rare earth elements were both abundant and relatively stable along the soil profile. The geochemical elements of N, P, S, Se, B, Zn, Cu, Y, Sc and La were the possible characteristic elements with vital influence on tobacco quality in Zhangjiajie mountain tobacco cultivation region.

     

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