The Effects Of Nitrogen And Leaves-remained Number On The Occurence Extent Of Tobacco Brown Spot And Output Value Of Tabacco

To determine the effects of nitrogen level and leaves-remained number on the occurence of tobacco brown spot and output value of tobacco, field experiment with split plot design was adopted. Yunyan87as tested variety, with nitrogen as the main plot, number of leaves as subplot,4nitrogen levels and5leaf number levels. The occurrence of disease incidence and disease index, and tobacco yield and output value were investigated. The effects of different nitrogen levers and number of leaves on brown spot index and yield and output value of flue-cured tobacco were analyzed. The main results were as follows:1. With the increasing of Nitrogen applied on tobacco, the infection rate of tobac co brown spot increased and the harmful degree increased significantly. The rate of plants infected brown spot was faster with N rate increasing. It was also found that, to apply Nitrogen in tobacco after topping, the infection of tobacco by Alternaria alte rnata increased significantly.2.Tobacco after topping, the relationship between the tobacco brown spot disease development and Leaves-remained Number was that red star disease incidence generally increased with the number of leaves increased and the disease tends to increase. Also with the growth of tobacco plants, the differences of treatment on different apparent leaf number increased gradually and reached the maximum rate till mid June before curing finished on the middle leaves,and it decreased gradually.3. In tabacco brown spot endemic area,the tobacco brown spot was easily explosed with the increased of N application and Leaves-remained Number. The result is:High nitrogen and high Leaves-remained Number with actual yield relative to the theoretical yield reduced more, relatively normal nitrogen and leaf number with no obvious increase. While tobacco benefits, value, and price with nagative increase with amount of nitrogen and increasing Leaves-remained Number4. From the benefit value of output, in tabacco brown spot endemic areas, the production ways of increasing the amount of Nitroen and incease the Leaves-remained Number with branching-after-topping after toppping to increase the unit yield output is irresonable. It can easily leads to tobacco brown spot disease exploses and negative production benefit.10.5kg pure nitrogen used on1200strains of tobacco,20leaves remained on each tabocco is more reasonable and safe. This level of nitrogen application amount and Leaves-remained Number is coordinated, while the occurrence of brown spot disease has been in some degree controll ed.the yield and quality were effected less and with higher production effeiciency.