Abstract: This study aimed to identify the optimal planting density for high yield and quality when growing alfalfa in central Inner Mongolia. In this study, alfalfa growth characteristics, forage yield and nutrient quality of the variety Caoyuan No. 3 were studied under four row spacing treatments (15, 30, 45 and 60 cm). The row spacing had a significant effect on the stem:leaf ratio (SLR), with SLR being lower under narrow raw spacing treatments (i.e. 15 and 30 cm row spacing treatments had significantly lower SLR than the 45 and 60 cm row spacings. The plant height and the fresh:dry ratio (FDR) increased with increased row spacing, while the forage yield decreased significantly with increased row spacing (i.e. yield was higher at 15 and 30 cm row spacings). The highest forage yields occurred in the second and third years and were 10813 kg drymatter (DM)·ha^-1 and 12574 kg DM·ha^-1, for the 30 and 15 cm row spacings, respectively. Planting density did not significantly affect crude fat and ash, but did significantly affect crude protein, acid detergent fiber, and neutral detergent fiber, as follows: crude protein was highest at 30 cm row spacing, neutral detergent fiber was lowest at the 15 cm row spacing, acid detergent fiber was lowest at the 45 cm row spacing, and the relative feed value was highest at the 15 cm row spacing. Considering all the forage yield and nutritional quality data, the recommended row spacing for alfalfa planting in the central region of Inner Mongolia is 15-30 cm.

Key words: alfalfa, density, yield, quality