Cutting management has been identified as a critical factor in the alfalfa production systems because it has a significant impact on maximizing yield and maintaining the forage quality. The objective of this experiment was to determine the proper cutting height according to harvesting time for optimizing nutrient yield and forage nutritive quality of alfalfa grown in alpine regions of Korea. Alfalfa was sown at a seeding rate of 30 kg/ha in August 2018 and harvested at four cuttings in 2019 (3 May, 2 July, 11 September, and 13 October). Cutting heights were adjusted at 5, 15, and 25 cm above the soil surface. Alfalfa plant was tallest at the third cutting (109 cm), which was on average 35 cm taller than the first or second cutting. Relative feed value (RFV) remained unaffected by cutting height at the first harvest, but increased consistently in subsequent harvests as cutting height increased. Alfalfa collected at the first and fourth cuttings had the highest RFV (mean 152), which was on average 8 and 67 units higher than the second and third harvests, respectively. At each harvest, in vitro dry matter digestibility was highest in alfalfa cut at a 25-cm height. Dry matter (DM) production at each cutting height was highest in the first cutting, accounting for on average 36-37% of total annual DM production, and lowest in the fourth harvest, accounting for about 11-13% of the total DM yield. The total dry matter production (in four harvests) was 4,218 kg/ha higher when alfalfa was subjected to a cutting height of 5 cm rather than 25 cm. Cutting height had no effect on total crude protein yield, but from the first to fourth cutting, the protein yield followed a decreasing trend. Finally, there were visible declines in forage nutritive quality when alfalfa was cut at a shorter height. However, the magnitude of difference in total forage yield may outweigh the slight decline in forage quality when alfalfa is cut at a lower height. The findings of this study could help the alfalfa growers make better harvest management decisions.

ABSTRACT
Ⅰ. INTRODUCTION
Ⅱ. MATERIALS AND METHODS
    1. Study location and alfalfa management
    2. Measurements
    3. Statistical analysis
Ⅲ. RESULTS
    1. Forage qualityEffects of cutting height
    2. Alfalfa forage yield
Ⅳ. DISCUSSION
Ⅴ. CONCLUSIONS
Ⅶ. REFERENCES

• Kim Hak Jin(Research Institute of Eco-Friendly Livestock Science, GBST, Seoul National University)
• Li Yan Fen(Graduate School of International Agriculture and Technology, Seoul National University)
• Jeong Eun Chan(Graduate School of International Agriculture and Technology, Seoul National University)
• Ahmadi Farhad(Research Institute of Eco-Friendly Livestock Science, GBST, Seoul National University)
• Kim Jong Geun(Graduate School of International Agriculture and Technology, Seoul National University/Research Institute of Eco-Friendly Livestock Science, GBST, Seoul National University) Corresponding author