This work was carried out to investigate uptake and utilization of nitrogen by different spilt dressings of nitrogen using heavy nitrogen in rice plants, and nitrogen mobilization into rice grain. Seedlings of two rice cultivars, cv. Ilpumbyeo, and cv. Saechucheongbyeo, were transplanted into a/2,000 pot. Nitrogen, phosphorus and potassium as fertilizer were applied to 16.5, 6.8, 8.6kg/10a, respectively. Heavy nitrogen (N15) included in applied nitrogen was 5 percent. As a result of analyzing soil chemical properties used in experiment, pH, total nitrogen, organic matter and silicate were 6.6, 0.1%, 1.0% and 110 g kg-1, respectively. Nitrogen mobilization into grain at ripening stage by split dressings of nitrogen was analyzed. Most of nitrogen applied as basal dressing transferred into grain, whereas nitrogen applied at tillering stage moved only 50%. Also, the mobilization into grain of nitrogen applied at tillering stage showed 1.5 fold higher than nitrogen applied at panicle initiation stage, therefore, it was confirmed that nitrogen applied at tillering stage was absorbed and utilized until panicle initiation stage. Nitrogen and amylose contents in grain were measured at ripening stage. A relation between nitrogen and amylose contents in grain showed negative correlation. Considering these results, split dressing of nitrogen by 50-20-20 or 50-20-30 was effective method not only to enrich nitrogen and amylose contents in grain, but also to reduce manpower. Table 1. Nitrogen, amylose and protein concentrations in rice grain at harvesting stage by different spilt dressings of nitrogen Cultivar Split dressings of nitrogen Nitrogen(%) Amylose(%) Protein(%) Ilpumbyeo 50-20-20-10 1.00 19.1 6.25 50-20-30- 0 0.91 19.3 5.74 50-20-20- 0 0.95 18.9 5.98 Saechucheongbyeo 50-20-20-10 0.92 20.5 5.89 50-20-30- 0 0.86 20.5 5.93 50-20-20- 0 0.94 20.4 5.83 Key words : nitrogen uptake, rice grain, spilt dressings, N15. Ju-Young Lee*, Byoung-Chun Jang, Jwa-Kyung Sung, Jae-Hong Park, So-Hyeon Park, Su-Yeon Lee, Ki-Sang Lee, Choong-Hoe Kim, Tae-Wan Kim1, and Young-Sang. Yoon2) Division of Plant Nutrition, NIAST, RDA, Suwon, Korea 1) Dept. of Plant Resources Science, Hankyong Nat. University, Ansung, Korea 2) Kongju National University, KongJu, Korea