The experiment was conducted to determine the effects of nitrogen fertilizer levels on seed production of Italian ryegrass (Lolium multiflorum Lam.) in mountainous regions of Gangwon Province. The 'Green Call' variety of Italian ryegrass was sown in Pyeongchang, Gangwon in September 2021. The experiment consisted of three nitrogen application levels (100, 120, and 140 N kg/ha) and was arranged in a randomized complete block design with three replications. Harvest was carried out on June 28. The plant height was tallest in the 140 N kg/ha treatment, but the difference was not statistically significant. Lodging resistance, disease resistance and winter hardiness showed no significant differences among treatments, although severe lodging occurred in all plots. The average spike length was 54.77 cm, with no significant difference among treatments, while the number of seeds per spike was highest in the 100 N kg/ha treatment. Seed yield increased with higher nitrogen levels, with an average of 2,820 kg/ha (based on air-dry weight). The average dry matter content of seeds and straw was 56.70% and 38.80%, respectively, with no significant differences among treatments. The average dry matter yield of residual straw after seed harvest was 4,144 kg/ha, with the highest yield observed in the 120 N kg/ha treatment. Meanwhile, the feed value of the harvested straw did not differ significantly among treatments. The average contents of ADF, NDF, CP, IVDMD, and TDN were 43.04%, 70.63%, 8.65%, 52.77%, and 54.88%, respectively. In conclusion, the optimal nitrogen fertilization level for Italian ryegrass seed production through autumn sowing in the mountainous areas of Gangwon Province was found to be 120 N kg/ha.

ABSTRACT
Ⅰ. INTRODUCTION
Ⅱ. MATERIALS AND METHODS
    1. Cultivation of Italian ryegrass
    2. Harvesting of Italian ryegrass
    3. Evaluation of seed characteristics
    4. Forage value analysis
    5. Weather conditions
    6. Statistical analysis
Ⅲ. RESULTS AND DISCUSSION
    1. Growth characteristics
    2. Seed characteristics
    3. Productivity of seed and straw
    4. Forage value of straw
Ⅳ. CONCLUSIONS
Ⅴ. ACKNOWLEDGEMENTS
Ⅵ. REFERENCES

• Wu Li Zhuang(Graduate School of International Agricultural Technology, SNU, Pyeongchang 25354, Republic of Korea)
• Xaysana Panyavong(Graduate School of International Agricultural Technology, SNU, Pyeongchang 25354, Republic of Korea)
• Yan Fen Li(Graduate School of International Agricultural Technology, SNU, Pyeongchang 25354, Republic of Korea)
• Jong Geun Kim(Graduate School of International Agricultural Technology, SNU, Pyeongchang 25354, Republic of Korea, Research Institute of Eco-friendly Livestock Science, GBST, SNU, Pyeongchang 25354, Republic of Korea) Corresponding author
• Ki Jun Choi(Research Institute of Eco-friendly Livestock Science, GBST, SNU, Pyeongchang 25354, Republic of Korea)