**Nitrogen Efficiency in Oilseed Rape and Its Physiological Mechanism**

Zhen-hua Zhang1,2,3,4, Hai-xing Song1,2,3,4 and Chunyun Guan5 *1Department of Plant Nutrition, College of Resources and Environment, Hunan Agricultural University, 2Hunan Provincial Key Laboratory of Plant Nutrition in Common University, Changsha, 3Hunan Provincial Key Laboratories of Farmland Pollution Control and Agricultural Resources Use, Changsha, 4National Engineering Laboratory of High Efficiency Utilization of Soil and Fertilizer Resoureces, Changsha, 5National Center of Oilseed Crops Improvement, Hunan Branch, Changsha, China* 
