The relationship among the changes of grass yield with the year after establishment, the uptake of fertilizer nitrogen, and soil nitrogen release in old meadows was studied from the viewpoint of decomposition of accumulated organic residues on the surface layer. Grass yield did not decline with the increase in the meadow age after the establishment under optimum fertilizer nitrogen application. However, when fertilizer nitrogen application was insufficient, grass yield of old meadows especially of those more than 9 years old decreased. The decrease resulted from the marked decrease in the first cutting yield of these old meadows. In such meadows, both the uptake of applied fertilizer nitrogen and release of soil nitrogen of the first cutting stage play an important role in maintaining the grass yield. These results were attributed to the large accumulation of organic residues on the surface layer and large C/N ratio. Immobilization of fertilizer nitrogen increased with the accumulation of organic residues, and the release of immobilized nitrogen decreased in the first growth period during which the soil temperature remained cool. Also, soil nitrogen mineralization potential (N01) of rapid release organic nitrogen decreased and apparent activation energy value (Ea1) increased with the increase of the meadow age. The sum of the second and the third cutting yields decreased due to the small amount of precipitation from July to August. This tendency was clearly observed in old meadows, due to the decrease in the decomposition of accumulated organic residues on the surface. There were no significant differences in the amount of total nitrogen in the 0 to 15 cm layer between a newly established meadow and a 15 years old meadow, although the distribution of nitrogen in the top 5 cm layer and 5 to 15 cm layer changed with the ageing of the meadow.