Contribution of white clover varieties in high-productivity systems under grazing and cutting

Two medium leaf size varieties of white clover (Trifolium repens L.) were g rown in mixture with a range of grass species and varieties in a field expe riment conducted over 4 years. The clovers were grown singly or as a blend in swards with a tetraploid perennial ryegrass (Lolium perenne L.), a diplo id Italian ryegrass (Lolium multiflorum? L.) or tetraploid hybrids between these two species (Lolium x boucheanum Kunth). These grasses were also grow n in monoculture. Swards were managed in a regime involving two periods of sheep grazing, two periods of cattle grazing and a silage cut in the same y ear for 4 years. The objectives of this experiment were 3-fold: (1) to exam ine the yield and persistency of white clover in highly productive systems with modern perennial, hybrid and Italian ryegrasses; (2) to compare the pe rformance of white clover varieties grown singly in mixture with grasses wi th their performance together as a blend, and (3) to examine the persistenc y of new Italian ryegrass varieties, exemplified by AberComo. The clover co ntent of the sward remained high throughout the experiment, with a mean of 31 % overall. Differences in clover yield between plots were largely attrib utable to the effects of companion grasses. Total yields were very similar in plots containing different clover varieties and in plots where these var ieties had been grown singly or as a blend. Grass yields in mixture were gr eater than those in monoculture but showed similar relative rankings. The d iploid Italian ryegrass variety AberComo showed an unexpectedly high yield in the 4th year of the experiment. The implications of these results for st rategies for productive, sustainable agriculture using modern white clover and ryegrass varieties are discussed.