Published online by Cambridge University Press: 27 March 2009
Ryegrass populations collected from intensively used swards, both leys and permanent pastures, were compared under spaced plant and sward conditions.
On average, the bred ryegrasses were higher yielding, more resistant to crown rust, and more persistent under intensive conditions than the permanent pasture populations, but there was no significant difference in cold-resistance between these two groups.
The potential yield of dry matter of the best of the permanent pasture populations was similar to that of the highest-yielding leys. Several of even the most intensively used pastures were, however, dominated by ryegrass that was not nearly as high yielding as the best of the bred varieties. In addition to differences in yield of dry matter, there was a wide range in persistency, resistance to low temperature and crown rust (Puccinia coronata), as well as in mean date and variance of inflorescence emergence and in yield of digestible organic matter in dry matter (DOMD). Thus, no one type of ryegrass could be associated with permanent pastures, even when the sample was restricted to a narrow range of managements associated with intensive use.
Some of the highest-yielding swards were based on complex mixtures of ryegrass cultivars; this might give rise to difficulty in relating management to stage of maturity and in predicting the composition of the sward established.
A comparison of survivor material derived from S·23 leys revealed no difference in yield of dry matter or DOMD under sward conditions. Other data, however, showed that the populations differed in yield as spaced plants, rust resistance, cold-hardiness, persistency and date and variance of inflorescence emergence.
There was no indication of ryegrass yield decreasing with the age of the ley from which the plants were derived.