Abstract
1. Three varieties of alfalfa (Moapa, Rhizoma and Williamsburg-chosen because of differences in their characteristics) were grown at densities of 2500 plants/m2, 625 plants/m2 and 25 plants/m2, to clarify the relation between stand density and yield of alfalfa swards. 2. In dry matter yield per unit area for three year period, all varieties showed the ranking order: 2500 plants/m2 plot=625 plants/m2 plot > 25 plants/m2 plot. The difference in yield between 25 plants/m2 plot and the other two plots was attributed to difference in yield of the first harvest in the first harvesting year. There were no significant differences among densities in annual yield in the second harvesting year and in yield of the first harvest in the third harvesting year. 3. As for varieties, the yield for three year period approximately showed the ranking order: Williamsburg > Rhizoma > Moapa. Although very small in variance compared with that of main effect, the interactions between variety and density suggested the possibilities that the ranking order of varieties was altered according to densities. 4. Plant numbers per square meter at the final harvest of this experiment were 94, 79, 15 plants/m2 for Moapa, 103, 83, 18 plants/m2 for Rhizoma and 130, 99, 18 plants/m2 for Williamsburg, in the order of 2500, 625 and 25 plants/m2 plots. It was suggested from the decreasing trend of plant numbers of Rhizoma that the surviving rate of a variety was affected by cutting regime. 5. Individual stem weight was inclined to become heavier as density decreased. Although the differences in stem weight between 2500 plants/m2 plot and 625 plants/m2 plot gradually disappeared as cutting schedule proceeded, the differences between 25 plants/m2 plot and the other two plots were observed even at the final harvest of this experiment. 6. Yield of alfalfa swards was maintained satisfactorily even at the density of approximately 15 plants per square meter.
