Abstract
It was previously reported that the correlation coefficient of green yield between spaced planting and solid seeding stands in Italian ryegrass strains was not high, and this phenomenon was presumably caused by the difference of response to density among the genotypes. This experiment was carried out to investigate varietal difference of density response, using six varieties at five levels of density. 1. Plant hight increases in proportion to increase in density to a certain extent, beyond which, however, it reaches plateau. 2. Tiller weight increases according to the increase of density in varieties having small tiller size, however, this tendency is reversed in varieties having large tiller size. 3. The logarithm of tiller number per plant decreases linearly as the logarithm of density increases and, either in more tillering varieties or in prostrate type varieties which have more bent leaves, coefficients (absolute value) of linear regression are larger than in others. 4. In varietal difference of density response for fresh weight per plant, there is the same tendency as in tiller number per plant, however, H1 ryegrass, which has high density response for tiller number per plant, is less responsive to density than othevs because its density response for tiller weight is low. 5. Green yield increases generally as density increases, however, in varieties having sharp response to density it reaches the maximum at the second denser plot in this experiment. 6. It is presumed that, by investigating light intensity within canopies, a degree of light-receiving efficiency is one of the factors to bring about varietal difference of density response.
