Early season dry matter production of three hybrid ryegrass (Lolium boucheanum) and two perennial ryegrass (Lolium perenne) cultivars

Hybrid ryegrass (HRG) is purported to have high overwinter growth characteristics and may have a role in Irish grassland systems. In a 3-year small-plot study at Fermoy, Cork, Ireland, the dry matter (DM) production and herbage quality of HRG cultivars in early spring were compared with diploid and tetraploid perennial ryegrass (PRG) cultivars. Treatments comprised ryegrass cultivars × defoliation managements × defoliation heights in a 5 × 3 × 2 factorial arrangement. The cultivars were Navan (tetraploid PRG), Foxtrot (diploid PRG), Foyle (tetraploid HRG), Brutus (diploid HRG) and Belleek (tetraploid HRG). Defoliation dates were: (A) 2 February and 20 April; (B) 2 February, 3 March and 20 April; and (C): 2 February, 23 March and 20 April. Defoliation heights were 4 and 7 cm, applied across each management. The HRG cultivars yielded similarly to cv. Navan on 2 February. Cumulative spring DM production was higher in cvs. Brutus and Belleek than all other cultivars. During this period, the managements A and B had similar DM yields (2765 kg DM ha^-1) but were greater than management C. Defoliating swards to 4 cm height increased DM yield compared with 7 cm height. Organic matter digestibility of grass at the silage-harvest growth stage was greater for PRG cultivars. The study indicates that early spring growth of the three HRG cultivars evaluated here was not sufficiently greater than the tetraploid PRG cv. Navan to compensate for their poorer midseason sward quality.