Field experiments and pot trials were carried out to elucidate the performances of italian ryegrass 2n, 4n, perennial ryegrass 2n and 4n, seeded at the various date and grown under the various photoperiods.
1) Both italian ryegrass 2n, 4n and perennial ryegrass 2n, 4n reduced their fresh weights by delaying of seeding time during spring season. And, the influence of delaying of seeding on their growth had appeared more severely on italian ryegrass than perennial ryegrass.
2) When temperature was below about 10℃, the effects of photoperiodic treatments on italian ryegrass were recognized more apparently on their plant height and tillering number.
3) However, as growing temperature became higher, effects of photoperiodic treatments on their growth became more difficult to be recognized.
4) Under lower temperature and short daylengh, both of italian and perennial ryegrass were increasing their tillers but not their plant height.
However, these effects of temperature and daylength were more remarkable on italian than on perennial ryegrass.
5) Both of diploid 4n of italian and perennial ryegrass had higher tolerable ability to summer depression than their 2n.
6) Delaying of seeding in spring was resulted in reducing of crude protein contents and its production in both of italian and perennial ryegrass but increasing of their crude fiber contents.
7) Contents of soluble carbohydrate of italian and perennial ryegrass were reduced by delayling of seeding. Constituent percentages of starch and fructosan to soluble carbohydrate were also influenced by shifting of seeding time, that is, when both of grasses were grown under higher temperature, percentages of fructosan to soluble carbohydrate became lower.