Abstract: This paper is part of The Nitrogen Nutritional Diagnosis and Recommendation as Top dressing Fertilizer N for Several Crops in North China. The rate of nitrogen application for four crops: spring wheat, winter wheat. spring corn and summer corn were studied in field plot experiment. The results showed that the optimum rate of nitrogen recommended for spring wheat, winter winter wheat and summer corn had a Significant difference at different sites.and were considered to be 158. 7～187. 8kghm-2,100. 0 ～ 155. 4 kghm-2 and 121. 0 ～ 228. 0 kghm-2. respectively. The optimum rate of phosphate recommendation had a unsignificant difference except for the spring wheat which varied from 71. 9 to 94. 4kghm-2. Based upon the research. the rate of nitrogen topdressing could be guided by the means of quick nitrate test in plant tissue.