Yields of perennial grasses growing in mixtures with annual species and the effect of perennials on total yields

Fifteen perennial grass cultivars were compared in cutting trials in the medium rainfall (about 700 mm/year) area of central New South Wales. The perennial grasses were shown to have different growth patterns. Siro 1146 phalaris (Phalaris aquatica x P. arundinacea), Brignoles cocksfoot (Dactylis glomerata) and Demeter fescue (Festuca arundinacea) had the highest dry matter yields in late spring and summer. The phalaris (Phalaris aquatica) cultivars Special Select, Sirosa, Sirocco and El Golea had the highest yields in autumn and winter, while Kangaroo Valley perennial ryegrass (Lolium perenne) and the cocksfoot cultivars, Berber, Brignoles and Currie, yielded well in spring. When the total yields of pastures containing perennial grasses and annual species were compared with the total yields of annual species alone, it was found that the perennials generally did not increase yields when present at relatively low plant densities (5-20 plants/m2) and growing with a vigorous annual species component. When present at higher plant densities (over 20 plants/ m2) perennial grasses only increased total yields in autumn and winter when soil moisture was low and annual species did not grow well. The probable effects on animal production of including perennial grasses in pasture mixes are discussed and it is concluded that the perennials are most likely to be beneficial in late spring and summer when annuals become less palatable and have lower digestibility.