EFFECTS OF NITROGEN AND COPPER FERTILIZATION ON RICE YIELD AND FERTIL- IZER NITROGEN EFFICIENCY: A 15N TRACER STUDY. Pakistan Journal of Scientific & Industrial Research [Internet]. 2004 Feb. 23 [cited 2026 Mar. 18];47(1):50-5. Available from: http://www.v2.pjsir.org/index.php/biological-sciences/article/view/1457