The growth responses of Lolium perenne to the weather during winter and spring at various altitudes in mid-Wales.
The seasonal growth patterns of micro-swards of a single genotype of perennial ryegrass cv. S23 were studied at 4 sites at various alt. in mid-Wales over the period Oct. 1973-July 1974. Upland sites were 1.5-2.5 deg C cooler and received 2-16% less insolation than lowland sites. The seasonal patterns of leaf DM production by single vegetative tillers at the 4 sites appeared to be largely controlled by temp. Leaf extension at all sites was consistently related to soil temp. Leaf extension at a given temp. was faster in the spring than in the autumn. Leaf appearance rate at a given temp. was greater in the spring than in the autumn and was greater in upland than in lowland sites. Even in winter there was a considerable turnover of leaf material because as new leaves appeared old ones were lost. Tillering rates were generally greatest at lowland sites and were greatest during early April-early May. Tillering rate was low or negative in winter. If the final autumn cut was made in Oct. as opposed to Sept., leaf extension, leaf length and leaf wt. were reduced by about 20% over the following 6 months, and tillering in the autumn was reduced, though tillering in the following spring was increased.