Extending the use up to the fourth year after sowing limits the number and length of generative tillers, number of spikelets per ear and seeds per spikelet and the perennial ryegrass seed yield. Under spring rainfall deficit in the first year of seed harvest the maximum perennial ryegrass yielding is observed during the second year. Over the four-year use for seeds the perennial ryegrass yields higher if sown with spring barley, as compared with spring pure stand; an earlier harvest of barley used for green crop does not increase the perennial ryegrass seed yield. The yielding of perennial ryegrass sown in autumn in the first year of full use was, mostly, lower and in the third and fourth years greater than when sown in spring in pure stand and with barley. Perennial ryegrass showed a poor reaction to a varied row-spacing with a tendency to limit yielding when cultivated at wide and very wide row spacing.

101-112