Tlis experiment was to study the effects of application rates of mineral N and cattle slurry on the dry matter yield and botanical compositions of Orchardgrass sward grown in 4 cuttings in a year. Annual rates of mineral N of O($N_0$), 120kg(($N_1$), 240kg(($N_2$) and 360kg/ha(($N_3$) were applied as urea, and cattle slurry applied at rates of O(($N_0=N_0$), $40m^3$($S_1$), $80m^3$(($S_2$) and $120m^3$($S_3$), suppling 120kg, 240kg and 360kgl ha, respectively. The results were summarized as follows; 1. The limiting annual application rates of mineral N and cattle slurry was estimated about 120kg/ ha. 2. The growth of Orchardgrass after the 3rd cut was decreased by summer depression. Consequently, the botanical compositions of Orchardgrass showed only 7.7% and 4.0% in 3rd and 4th cut, respectively. However, the 15 and 17 species of weeds originated in 3rd and 4th cut. 3. The botanical compositions of Amaranthus mangostanus in 3rd cut and Portulacea aleracea in 4th cut were greatly increased with application rates of cattle sluny. 4. Relative efficiency of cattle sluny for the dry matter production of Orchardgrass as compared to mineral N were 93.396, 99.5% and 113.6% in 120kg, 240kg and 360kglha at rates of cattle slurry, respectively.