Effects of nitrogen sources on nitrogen utilization and growth of flue-cured tobacco in the floating-seeding system

The utilization of four different forms of nitrogen, NO3--N, NH4+-N, (NH2)2CO-N and NH4NO3, in the flue-cured tobacco floating-seeding system was studied. The results indicate that the highest N apparent utilization efficiency is in the NO3--N flue-cured tobacco floating-seeding system, and is followed by the (NH2)2CO-N, NH4NO3 and NH4+-N systems. The N actual utilization efficiency is in the order: NH4NO3(NH2)2CO-NNO3--N＞NH4+-N. Tobacco seedling indices, such as root activity, photosynthetic pigment content and degree of lignification in the NH4NO3 or (NH2)2CO-N systems are significantly higher than those in the NO3--N systems. Therefore, urea plus a small quantity of NO3--N could be an optimum selection of N source to improve the qualities of tobacco seedlings and economic fertilization in the floating-seedling system.