Abundance And Deficiency Index Of Soil Zinc And Diagnosis Of Zinc Nutrition In Flue-cured Tobacco

Zinc is an important microelement in flue-cured tobacco, and it plays an important part in the flue-cured tobacco growth, development, and nutrition metabolism, and besides, it increases the yield and promotes the quality of the tobacco leaves profoundly. There are about63%of soils which the Zinc content is below1.00mg/kg in tobacco growth area of Enshi, Hubei province, indicating that the soil zinc deficiency is very serious in tobacca production. Thus, soil Zinc fertility has become an important factor that limits the high yield and quality of flue-cured tobacco, and applying zinc fertilizer is an important measure to improve the yield and quality of the flue-cured tobacco. However, in practical production, for lack of nutrition diagnosis index to guide the rational fertilization in flue-cured tobacco, the effects of zinc fertilizer are greatly influenced. Based on this, a series of soil pot and field experiments were carried out in2011-2013to study the effects of different soil fertility of zinc and applying zinc fertilizer on flue-cured tobacco growth, yield value, and absorption of mineral nutrition elements in order to achieve the abundance index of soil zinc fertility and the zinc nutrition diagnosis index of flue-cured tobacco. The study was to provide scientific theoretical basis for reasonable application of zinc fertilizer in production of flue-cured tobacco. The results of the study are summarized as follows:1. Flue-cured tobacco soil pot and field experiments were employed to study the effects of different soil available zinc and application of zinc fertilizer on the zinc content of flue-cured tobacco at different parts of the plant and at different growth stages. The results showed that the zinc content in each part of the flue-cured tobacco increased with soil available zinc content, but when soil available zinc content was above a threshold, the zinc content in each part of the flue-cured tobacco no longer increased. Based on3years of soil pot and field experiments, the threshold of soil available zinc content for Enshi tobacco growth soils were determined as1.70-1.90mg/kg, which suggested that, when the soil was below the critical value, applying zinc fertilizer increase zinc content, satisfy the zinc nutrition, and improve the yield and quality of flue-cured tobacco.2. The optimum zinc contents of flue-cured tobacco were86-100mg/kg in leaves at rosette stage, and83-95mg/kg in the upper leaves at topping period. The optimum content of zinc could be used as zinc nutritioni diagnosis index.3. The ratio of N/Zn also increased with the increasing contents of soil available zinc. Experimental results indicated that the critical areas of the ratio values corresponding soil available zinc content were1.57-1.90mg/kg. Below the values, applying zinc fertilizer made the N/Zn ratios of flue-cured tobacco at different growth stages drop significantly, The N/Zn ratios of536-580were suitable in the rosette stage, and for upper leaves, middle leaves, lower leaves and stem at topping stages, were516-593,390-422,422-208, and1897-191respectively.4. Similarly, the P/Zn ratios of each part of the flue-cured tobacco decreased significantly with the increase of soil available zinc content. The critical areas corresponded the soil available zinc content of1.60-1.90mg/kg. Below the critical areas, applying zinc fertilizer decreased P/Zn ratios significantly. The optimium P/Zn ratios were19-35in leaves at the rosette stage, and50-54,25-29,11-12in upper leaves, middle leaves and lower leaves at topping stages.5. In addition, soil available zinc content and application of zinc fertilizers affected the content of nitrogen, phosphorus, potassium, but with a quadratic curve relationship. The maximum content of these nutrients corresponded the soil content of available zinc in flue-cured tobacco soil were around1.70-1.90mg/kg.6. Different soil fertility of zinc had a significant influence on flue-cured tobacco growth as well as the yield and output value of tobacco, however, only the effects on the plant height of flue-cured tobacco was significantly positive.