Effects Of Combined Application Of Molybdenum And Nitrogen On Development,Formation Of Yield And Quality Of Flue-cured Tobacco

Flue-cured tobacco is an important cash crop in China.Nitrogen and Molybdenum have significant impacts on the yield and quality of flue-cured tobacco.However,the soil in most flue-cured tobacco-growing areas in China lacks Molybdenum,which has affected the growth and development of tobacco to some extent.At the same time,excessive application of Nitrogen fertilizers has also resulted in the decline of the quality of the tobacco leaves.Therefore,based on a summary of the research progress on the effects of Nitrogen and Molybdenum application on flue-cured tobacco in China and other countries,this study investigated the effects of Molybdenum and Nitrogen interaction on Nitrogen and Molybdenum absorption of flue-cured tobacco were studied systematically,based on both pot and field experiments.The effects on the growth,development,yield,and quality of flue-cured tobacco were also analyzed.The main results were as follows:1.Effects of combined application of Molybdenum and Nitrogen on root traits of flue-cured tobacco.The results were showed that Nitrogen concentration in rhizosphere was the main factor affecting the development of root system of flue-cured tobacco,the development of root system was affected by nitrogen application rate,the root activity was decreased at the N0 level on the 45th days,and the root activity was only 29.65%of the highest treatment at the N0 level on the 90th days,premature aging phenomenon of tobacco leaves was appeared at the same time.On the N0.3 level,nitrogen uptake could be promoted at the later stage and the maturity of tobacco plant could be delayed with root development.Molybdenum Application promoted root development,root volume and root activity were mainly affected by Molybdenum application.The Molybdenum and Nitrogen interaction regulated root development which adapt to the change of Nitrogen concentration in rhizosphere,and absorption and transformation of Nitrogen were promoted.2.Effects of combined application of Molybdenum and Nitrogen on dry matter accumulation volume and accumulation rate of flue-cured tobacco at different stages of growth.The results were showed that the dry matter accumulation volume and accumulation rate in flue-cured tobacco were improved significantly by both Nitrogen and Molybdenum application,and the combined application of Molybdenum and Nitrogen had a significant synergistic effect on the dry matter accumulation in the vigorous growing stage and the early maturing stage.Flue-cured tobacco was susceptible to thecombined application of Molybdenum and Nitrogen from the vigorous growing stage until the lower leaves were harvested.Nitrogen was the dominant factor affecting dry matter accumulation volume,while Molybdenum promoted dry matter accumulation.Thecombined application of Molybdenum and Nitrogen also had a significant synergistic effect on dry matter accumulation in flue-cured tobacco,and affected the growth and development process of flue-cured tobacco.Further,thecombined application of Molybdenum and Nitrogen significantly affected the distribution proportions of dry matter in the roots,stems and leaves of flue-cured tobacco,and Molybdenum application was conducive to improving the distribution proportion in the leaves.3.Effects of combined application of Molybdenum and Nitrogen on Nitrogen uptake and distribution in flue-cured tobacco.The results were showed that the Nitrogen content in roots,stems,and leaves were increased significantly by increasing the Nitrogen application level and was regulated by Molybdenum.The Nitrogen accumulation volume of flue-cured tobacco leaves and the whole plant increased significantly by increasing the application level of both Nitrogen and Molybdenum.The combined application of Molybdenum and Nitrogen had a synergistic effect on Nitrogen accumulation volume.The Nitrogen accumulation rate tended to decrease gradually with the development of growth period.With increasing Nitrogen level,Nitrogen distribution proportion in leaves was significantly increased and Nitrogen distribution proportions in roots and stems were reduced significantly.Molybdenum and the combined application of Molybdenum and Nitrogen had significant effects on Nitrogen distribution proportions in roots and stems at middle and late growth stages.At the same level of nitrogen application,Molybdenum application was beneficial to increase Nitrogen harvest index.Under the condition of nitrogen application,the Nitrogen use efficiency of N0.15Mo0.15 treatment was the highest in 2012,and the nitrogen use efficiency of N0.15Mo0.3 treatment was the highest in 2013.The production efficiency of Nitrogen fertilizer decreased significantly under high Nitrogen level.The application of Molybdenum was beneficial to increase Nitrogen use efficiency and Nitrogen production efficiency of flue-cured tobacco.At N0.15 level,he application of Molybdenum increased nitrogen fertilizer efficiency to 39.3 g.g-1 in 2012,and 37.45 g.g-1 in 2013.4.Effects of combined application of Molybdenum and Nitrogen on absorption and accumulation of Molybdenum and other major minerals during flue-cured tobacco development.The results were showed that during the growing period in the field,Molybdenum application level significantly affected the content of Molybdenum in tobacco leaves,whereas,Nitrogen application level and the combined application of Molybdenum and Nitrogen did not significantly affect the Molybdenum content in tobacco leaves.Molybdenum application,Nitrogen application,and thecombined application of Molybdenum and Nitrogen had an extremely significant effect on the accumulation volume of Molybdenum in flue-cured tobacco leaves.At the same level of Nitrogen application,the content and accumulation volume of Molybdenum in leaves tended to increase with the increase in Molybdenum application level.After curing,the Molybdenum content of different leaf positions was as follows:lower leaves>middle leaves>upper leaves.Molybdenum application significantly increased the content of Molybdenum,and the content of Molybdenum in the leaves of the three parts increased with the increase in Molybdenum application level.Nitrogen and Molybdenum interaction had an extremely significant effect on the content of Molybdenum in the upper leaves.5.Effects of combined application of Molybdenum and Nitrogen on plastid pigment content and carbon-nitrogen metabolism in flue-cured tobacco.The results were showed that an increase in Nitrogen application level increased the plastid pigment content of tobacco leaves,and Nitrogen was the main factor affecting this content.An increase in Molybdenum fertilizer application promoted the pigment accumulation in tobacco leaves at the early stage and accelerated the degradation at the maturing stage.Thecombined application of Molybdenum and Nitrogen had a significant synergistic effect on the pigment degradation in tobacco leaves at the maturing stage.The nitrate reductase activity of leaves was significantly improved,and the decline of nitrate reductase activity was delayed by increasing Nitrogen and Molybdenum fertilizer application levels.Increasing Nitrogen fertilizer application level and medium Molybdenum fertilizer application improved the activity of invertase,but high Molybdenum application had no significant effect on the activity of invertase.Increasing Nitrogen fertilizer application level was beneficial for increasing amylase activity and delaying its activity peak,while increasing Molybdenum fertilizer application level was conducive to the increase of amylase activity.Increasing Nitrogen fertilizer application level was beneficial for the increase of the soluble protein content at the vigorous growth stage.Increasing Molybdenum fertilizer application level was beneficial for the increase of soluble protein content at the medium level of Nitrogen application.Under an appropriate Nitrogen level,Molybdenum application improved the balance of carbon-nitrogen metabolism,promoted photosynthesis,and facilitated the synthesis and accumulation of carbon-and nitrogen-containing compounds.6.Effects of combined application of Molybdenum and Nitrogen on photosynthetic parameters of flue-cured tobacco.The results were showed that the application of Nitrogen could promote the process of photosynthetic carbon assimilation,and the application of Molybdenum could improve the stability of light system and the photosynthetic rate of tobacco leaves.The photosynthetic rate increased significantly and the non-photochemical quenching coefficient decreased significantly under the treatment of middle Nitrogen and middle Molybdenum,which alleviated the damage of photo-system caused by the surge of active oxygen during leaf Senescence,and was beneficial to the enhancement of photosynthetic carbon metabolism.Under medium Nitrogen level,the actual photochemical rate and the conversion rate of original light energy increased with the increase of Molybdenum fertilizer.Under high Nitrogen level,stomatal conductance,transpiration rate,photochemical quenching coefficient,electron transfer rate and intercellular carbon dioxide concentration of flue-cured tobacco increased with the increase of Molybdenum fertilizer.The interaction of Molybdenum and Nitrogen could make the light energy absorbed by the antenna pigment transfer to the photochemical pathway,and the effective utilization of light energy could be promoted finally.The interaction of Molybdenum and Nitrogen could improve the efficiency of light energy utilization and enhance the photosynthetic carbon assimilation of tobacco.Furthermore,the accumulation of dry matter of flue-cured tobacco was promoted and the yield formation was promoted.7.Effects of combined application of Molybdenum and Nitrogen on flue-cured tobacco yield,output value,and its constituent elements.The results were showed that the effects of Molybdenum and Nitrogen on the effective leaf number and dry matter weight per plant were extremely significant,and thecombined application of Molybdenum and Nitrogen had a synergistic effect.Nitrogen application volume contributed the most to the dry matter accumulation volume in flue-cured tobacco leaves.They are the basis for the influence of Molybdenum and Nitrogen interaction on the yield of flue-cured tobacco.Molybdenum and Nitrogen interaction significantly affected the yield of flue-cured tobacco products,which was another factor affecting the yield of flue-cured tobacco.The interaction increased the yield by increasing dry matter accumulation in leaves,which was evidenced by the significantly increased yield of upper leaves and middle leaves.The range of middle leaves yield among treatments reached 54.55 kg,and that of upper leaves yield reached 80.12 kg.The effect of Molybdenum and Nitrogen interaction had extremely significant effects on the position structure,grade structure,and output value of cured tobacco leaves.The combined application of N0.15 and Molybdenum was beneficial for the improvement of the grade structure of tobacco leaves and for the increase of the output value per 667 m2.The effect of Molybdenum and Nitrogen interaction was significant.N0.3 significantly increased the proportion of upper leaves and the yield of ungraded tobacco,and Molybdenum application improved the curing characteristics of tobacco leaves,thereby reducing the yield of ungraded tobacco.Nitrogen fertilizer application increased the output value mainly by increasing the yield of tobacco,while Molybdenum fertilizer application increased the output value mainly by increasing the yield as well as the proportion of high-and medium-grade tobacco.Molybdenum and Nitrogen interaction promoted the quality and yield of flue-cured tobacco and improved its grade structure.The yield per 667 m2 of high-grade tobacco treated with N0.15 Mo0.3 was 103.92 kg,with a proportion of 52.92%,and that of medium-grade tobacco was 83.76 kg,with a proportion of 42.68%.8.Effects of combined application of Molybdenum and Nitrogen on the yield,output value and its constituent elements of flue-cured tobacco.The results were showed that the application of Nitrogen and Molybdenum fertilizer significantly increased the total Nitrogen content of cured tobacco leaves,and the effect of Molybdenum and Nitrogen interaction was extremely significant.Both Molybdenum and Nitrogen application increased the nicotine content of upper leaves,but Molybdenum application reduced the nicotine content of the middle and lower leaves at the level of N0.3.The Nitrogen application level significantly affected the sugar content of cured tobacco leaves.The Molybdenum application as well as thecombined application of Molybdenum and Nitrogen had different effects on the sugar content of flue-cured tobacco under the pot and field conditions,and the interaction had greater effects on reducing sugar than on total sugar.Increasing the Nitrogen application level significantly increased the starch content of cured tobacco leaves,whereas increasing the Molybdenum application level significantly reduced the starch content.The effect of Molybdenum and Nitrogen interaction was significant.The content of petroleum ether extract in cured tobacco leaves was significantly increased by applying Molybdenum and Nitrogen.The effect of Molybdenum and Nitrogen interaction was significant in the lower leaves,but was not significant in the middle and upper leaves.The combined application of Molybdenum and Nitrogen was beneficial for improving the coordination of chemical components in tobacco leaves.9.Effects of Molybdenum application threshold and different molybdenum application methods on the yellowing characteristics of upper leaves of flue-cured tobacco.The results were showed that:The molybdenum concentration in rhizosphere soil could be adjusted to 0.15mg.kg-1,which could be used as the application threshold of Molybdenum.The application of molybdenum fertilizer was the best measures to improve the yield and quality of flue-cured tobacco at different times.the yellowing uniformity of single leaf could be improved and the mature yellowing of tobacco leaves were promoted through the application of molybdenum fertilizer in the early stage.The uniformity of yellowing of upper leaves was increased and the yellowing time was delayed by spraying Molybdenum fertilizer on upper leaves at the later stage.