Effects of plant density on alfalfa (Medicago sativa L.) seed yield in western Heilongjiang areas

Alfalfa (Medicago sativa L.) is known as the "king of forages". The aim of the current study is to determine the optimum planting density as the key cultivation technique for high yield of alfalfa seed. Alfalfa variety (Longmu 801) was planted in experimental fields from 2014 to 2017. In the planting density test, the row spacing was 65, 80, and 95 cm, and the plant spacing was 30, 45, 60, 75, and 90 cm. The seed yield and yield components in the row spacing and plant spacing tests were measured. On the basis of 3 years average of the experimental data, the highest seed yield of 225.49 kg ha(-1) was obtained with row spacing vs plant spacing of 65 and 60 cm, respectively. Correlation analysis showed a significant positive correlation between the racemes per stem, pods per raceme, pods per stem, seeds per pod, and the seed yield. These results suggested that Longmu 801 should be cultivated with 65 cm row spacing and 60 cm plant spacing to maximize seed yields in western Heilongjiang areas.