NITROGEN NUTRITIONAL DIAGNOSIS AND RECOMMENDATION AS TOPDRESSING FERTXLIZER N FOR SEVERAL CROPS IN NORTH CHINA Ⅲ. Nitrogen nutritional diagnosis and recommendation as topdressing fertilizer N for spring wheat

Two quick test methods (diphenylamine method and nitrate test strip) for diagnosising nitrogen nutritional status in spring wheat were studled in field expriment.The results suggested that the optimum diagnosis parts of plants was the stem base just prior to jointing stage, and the critical values of nitrate was considered to be 2. 55 (diphenylamine method) and 2600mgkg-1NO3-(nitrate test stripe). Based upon the results from nitrogen nutritional diagnosis. a fertilizer N topdressing recommendation model was set up.