Evaluation of seven Italian and hybrid ryegrasses under sheep grazing in Southland, New Zealand

Abstract

Abstract Three Italian and four hybrid ryegrass cultivars (Lolium multiflorum and L. boucheanum Syn. L. hybridum) sown with the white clover cultivar Grasslands Huia (Trifolium repens), were evaluated under frequent/hard grazing or infrequent/ lax grazing. Dry matter (DM) yields and species composition were assessed for 5½ years. Ryegrass tiller and white clover growing point population densities were determined annually, and leafrstem ratios every spring and autumn. Ryegrass tillers were assessed for infection with an Acremonium‐like endophytic fungus and bacterial wilt disease (Xanthomonas campestris pv. graminis). The Italian ryegrass cultivars Moata and Concord had total yields 33% greater than the mean of the other cultivars (1800 kg DM/ha) over the first autumn and winter. The Italian cultivars persisted well for 3 years, except Concord which had a high incidence (34%) of bacterial wilt. Of the hybrid ryegrasses, cultivar Corvette had high ryegrass yields in the first year (9800 kg DM/ha), similar to those of the Italian cultivars, and continued to be high‐yielding and persistent throughout the experiment. However, its degree of aftermath heading was high and probably reduced ryegrass herbage quality in summer and autumn. An inverse relationship between ryegrass yield and white clover yield resulted in few significant differences in total yields between cultivars. Infrequent/lax grazing maximised total annual yields (+5%) but decreased white clover yields (‐13%). With the importance placed on achieving high white clover growth in the cool temperate environment of Southland, choice of ryegrass cultivar should consider factors such as pasture quality (primarily percentage composition of white clover), tolerance of the cultivar to a range of grazing managements, and seasonal herbage production. The presence or absence of endophyte was not considered a major factor influencing the long‐term persistence or productivity of the cultivars evaluated at this site.