임간초지 개발에 관한 연구 XI. 차광조건하에서 질소시비수준이 계절별 , 생육시기별 목초생육과 수량 및 초지식생에 미치는 영향

Studies on the Grassland Development In the Forest XI. Effect of nitrogen fertilization on grass growth , yield and botanical composition by growing season and growth stage in in pasture under shade condition

This experiment was carried out to determine the effects of nitrogen(N) fertilizer levels (0, 120, 240 and 360kg $ha^{-1}Y^{-1}$ Y-') on seasonal grass growth, dry matter (DM) yield and botanical composition in pasture under shade condition. Investigation date was on 7 , 14, 21, 28 and 35 days after harvesting in spring (May), summer (July) and autumn (Sept.), 1988, respectively. Shade degree was controlled artificially ca. 45-50%, and each annual level of N was distributed 5 times equally. Grass growth and DM productivity were most vigorous in spring. Higher DM yield was produced with N 240 kg spring, and Nl2Okg in summer and autumn. Higher significant relationships, in spring, were found between grass height and DM, and N level and DM yield. However, low relationships were observed between those in summer and autumn. In botanical composition, grass coverage was decreased in summer and autumn, and bareland was increased, especially in higher N plots. Based on the results, it is suggested that 200kg $ha^{-1}$ of N in this experiment is more effective for forage production and pasture persistence. Also a littie more amount of N (50-70kg $time^{-1}$) in spring, and low level of N (20-30kg $time^{-1}$) in summer and autumn may be desirable.