Effects of Nitrogen Application on Nitrogen Accumulation, Distribution and Soil Nitrogen Mineralization

A field experiment was carried out to investigate the effect of nitrogen application rates on flue-cured tobacco nitrogen accumulation, distribution and soil nitrogen mineralization on brown soil. The results indicated that the nitrogen accumulation of organs and whole shoot increased with higher nitrogen rates. Fast nitrogen accumulation stage of N0 treatment occurred from 9 to 11 weeks after transplanting (WAT), but for the treatments of nitrogen application, the fast accumulation stage occurred two weeks earlier, and the nitrogen accumulation amount still increased after the fast nitrogen accumulation stage, while it decreased in the untreated N0. The nitrogen distribution proportion (NDP) of different tobacco organs were in the decreasing order: leaf＞stem＞root, the NDP of middle leaves and lower leaves reduced, the NDP of stem increased, and the NDP of root changed gently along with the development process. The occurring time of the maximum distribution proportion of upper leaves of N0, treatment N1 and treatment N2 was 11 WAT, 13 WAT and 15 WAT, respectively, which implied that it was delayed by nitrogen application. The soil Nmin and nitrogen apparent mineralization amount improved with the increasing nitrogen application rates, apex value of soil Nmin and nitrogen apparent mineralization amount were delayed by applying nitrogen. The nitrogen apparent mineralization amount of different treatments was above zero from 0 to 5 WAT, and was blow zero after 6 WAT, irrespective of nitrogen application amount.