Effects of nitrogen management on yield, quality, nitrogen accumulation and its transportation of watermelon in gravelmulched field. Effects of nitrogen fertilization on nitrogen use efficiency and yield of machine-transplanted long–age rice seedings Application of relative SPAD values for nitrogen fertilizer management of different cultivars of summer maize Response of winter wheat to different nitrogen managements in North Central China Effects of Different Paddy Field Drainage Degrees and Panicle Nitrogen Fertilizer Managements on Photosynthetic Productivity and Nitrogen Utilization of Rice under Triangle-Planted System of Rice Intensification