Boron Nutrition Diagnosis Of Flue-cured Tobacco And The Abundance And Deficiency Index Of Soil Boron

Boron (B) is one of the most important trace nutrient elements of Flue-cured Tobacco; it plays an important role in metabolism and growth of Flue-cured Tobacco.In recent years, the deficiency of trace elements especially boron is more and more serious in EnShi District, where the deficient area is more than90%occupied by tobacco. B deficiency becomes one of the key limiting factors of flue-cured tobacco’s quality. In this study, Nicotiana tabacum Yunyan87was used in a series of pot and field experiments during2011to2012to study the abundance and deficiency index of soil B and B nutrition diagnosis of flue-cured tobacco. To provide the scientific guidance for the production of good quality of flue-cured tobacco, the main results were as follows:1. Soil available B contents significantly affect the absorption and distribution of flue-cured tobacco boron uptake, B contents in flue-cured tobacco leaves and stems in different periods were varied with the soil B content (0.02-1.29mg/kg), firstly it increased, and then decreased significantly with the increasing of soil available B content. The critical values in Enshi tobacco-growing soil available B content is0.46-0.75mg/kg. Experiments also show that, when the available boron content of soil is lower than the critical values, the fertilizer’s amount of B can improve the B contents of Flue-cured tobacco. Without fertilization treatment comparison, boron fertilizer increased7.1%-12.4%boron content of Flue-cured tobacco.2. The activity of SOD, POD enzyme reached maximum at value, when the soil available B content was0.75mg/kg. The average enzyme activity in rosette stage SOD, POD were65,600U mg"1protein min-1. At the same time, MDA contents decreased firstly and then increased significantly with the increase of soil available B content in the rosette stage. When the available B contents in soil were0.8mg/kg, the MDA decreased significantly in rosette stage.3. With the increasing of soil available B, the nitrogen contents in rosette stage and topping stage of leaf and stem increased firstly and then decreased. When the soil available B content was0.66-0.8mg/kg, the nitrogen contents in rosette stage and topping stage of leaf reached at the maximum value, respectively60.1,49.9g/kg in2011. Pot experiment showed that the soil available B contents0.66-0.8mg/kg was the turning point of the nitrogen absorption of flue-cured tobacco, soil boron content below or above this level will inhibit the absorption of nitrogen in Flue-cured tobacco.4. Soil available B content and B fertilizer application significantly affected the phosphorus content of flue-cured tobacco leaf, and the interaction of B fertilizer application and soil available B content was significant. With the increasing of soil available B content changes in the rosette stage, the phosphorus content of leaf and stem first increased and then decreased according to the B treatments, corresponding soil available B content was0.56-0.98mg/kg.5. With the increasing of soil available B content, the potassium content of leaf and stem in rosette stage increased firstly and then decreased significantly. Soil available boron and boron fertilizers significantly affected the potassium content in different parts of flue-cured tobacco in different period. When soil available B content was0.73mg/kg, the potassium content in flue-cured tobacco leaves reached the maximum value in the pot experiment2012. At the same time, the fertilizer of boron could significantly increased the content of potassium in Flue-cured tobacco.6. With the increasing of soil available B content, the Mg/B ratios of leaf and stem first increased and then decreased significantly. When soil available B content was0.75mg/kg, the Mg/B ratios at topping stage leaves and stems reached at maximum value,200.5and104.2respectively. At the same time, the fertilizer of boron could significantly reduce the Mg/B ratios in rosette stage and topping stage. Compared with no fertilizer, boron fertilizer makes the Mg/B ratio in rosette stage and topping stage smoke decreased average by19.7%,19.5%respectively. The Mg/B ratios in rosette and topping stages of smoke were reduced significantly under B fertilization by19.7%and19.5%respectively.7. The Mg/B ratios of leaf and stem first increased and then decreased significantly with the increasing of soil available B content. Soil available B content was0.75mg/kg; the Ca/B ratio in topping stage of middle leaf reached the lowest value. At the same time, the fertilizer of B significantly reduce the Ca/B ratio in flue-cured tobacco leaves, leaf and stem decreased12.1%and9.8%respectively.