Studies On The Absorption And The Distribution Of Nitrogen In Flue-cured Tobacco Based On¹⁵N

Nitrogen absorption and distribution law of flue-cured tobacco in full aroma stylecore-producing area （Jiaxian county）and edge-producing area （Fangcheng county） of Henanprovince was studied by using¹⁵N-labelled field experiment in2011.The results are as follows:1. Nitrogen distribution at different growth stages in flue-cured tobaccoNitrogen accumulation ability of tobacco plant was strongest during40-60days aftertransplanting, and then it was weaker gradually, as well as the loss of nitrogen in tobacco plant wasappeared in the later growth period. The amounts of total nitrogen in different tobacco organsthroughout all the growing period were in the order of leaves>stems>roots; Topping destroyed thegrowth center of the tobacco plant, the nitrogen accumulation in tobacco plant increasedsignificantly after topping; The tobacco plant in Jiaxian grew weakly stage and accumulated verylittle nitrogen during the early, but it absorbed soil nitrogen excessively during the later growingstage and lead to mature period postponed; Most nitrogen of flue-cured tobacco was derived fromsoil, and with growth period extending and leaf position ascending, the ratio of soil nitrogen to totalnitrogen increased evidently, and even in the later growth period tobacco plant still could absorbnitrogen from soil.2. Nitrogen absorption law of different forms in flue-cured tobaccoBased on the same amount of nitrogen application, the tobacco plant accumulated more nitratenitrogen than ammonium nitrogen and most of the nitrate nitrogen accumulated in leaves, theutilization of nitrate was significantly higher than ammonium nitrogen during all the growing stage;Tobacco plant absorbed much nitrate nitrogen before40days after transplanting in Fangcheng, thenitrate nitrogen in basic fertilizer was conducive to initial growth of the tobacco plant and thefertilizer efficiency of the ammonium was more durable than nitrate; with leaf position ascendingthe ratio of different nitrogen forms to total nitrogen reduced evidently especially during60-80daysafter transplanting.3. The absorption law of top dressing in flue-cured tobaccoMost of the nitrogen from top dressing accumulated in leaves during the early growing stage,and the accumulation of top dressing in stems also increased vigorous during the middle growingstage; The nitrogen of top dressing was important to meet nitrogen demand of the flue-cured tobacco during the vigorous growing period and nitrogen utilization improving; The ratio of the topdressing nitrogen to total nitrogen in lower leaves was highest, the middle leaves secondly and theupper leaves lowest.4. The absorption law of nitrogen in mature leavesThe ratio of fertilizer nitrogen to total nitrogen reduced evidently with leaf position ascendingin mature leaves in two pilot sites especially in Jiaxian（The proportion of fertilizer nitrogen to totalin upper leaves was only7.57%because of accumulating large amounts of soil nitrogen）; Themature leaves of flue-tobacco accumulated more nitrate nitrogen than ammonium nitrogen and therewas not significant difference between the different parts of the tobacco plant; With leaf positionascending the ratio of top dressing nitrogen to total nitrogen increased evidently in Fangcheng butnot the case in Jiaxian.5. The utilization of fertilizer nitrogenThe utilization of fertilizer nitrogen significantly increased during40-60days aftertransplanting in two pilot sites, it continuously reduced after reaching peak and the growth periodlasted longer the nitrogen utilization decreased more significantly; The nitrogen utilization of topdressing was lower than basic fertilizer before40days after transplanting, since then the utilizationof topdressing was significantly higher than the basal nitrogen; The utilization of ammoniumnitrogen was significantly lower than the nitrate nitrogen during entire growth period especiallyduring40days after transplanting in Fangcheng.