Growth, persistence, and rust sensitivity of irrigated perennial temperate grasses in the Queensland subtropics

Abstract

The growth, persistence, and rust sensitivity of a range of temperate grasses were measured to assess their potential for irrigated pastures in the subtropics. Characteristics considered important for adaptation to the subtropics include a relatively even growth rate throughout the year, rust tolerance, and the ability to persist under humid conditions. Cultivars and experimental lines from Lolium perenne (perennial ryegrass), L. rnultiflorum (Italian ryegrass), Festuca arundiizacea (fescue), Festuca x Lolium (festulolium), Bromus spp. (prairie grass and bromes), Dactylis glomerata (cocksfoot), and Phalaris aquatica (phalaris) were sown at Gatton, south-eastern Queensland, in pure stands or mixtures of annual and perennial grasses, using high seeding rates, 50 kg N/ha.defoliation, and full irrigation throughout the year. As a group, the fescues were the highest yielding and most persistent over 2 years, with AU Triumph the highest yielding cultivar. Maru phalaris was the most persistent grass, increasing from a frequency of 85% at the end of the first year to 100% at the end of the second year. Perennial ryegrass yields were about two-thirds those of the fescues, with a frequency of around 70% after 2 years. Dobson was the best ryegrass, producing a greater proportion of its forage in summer and increasing its density over the 2 years compared with the other perennial ryegrasses. Mixtures of annual ryegrass and fescue cultivars produced yields equivalent to pure fescue swards, with production dominated by annual ryegrass in the first year and by fescue in the second. Matua prairie grass was high yielding, but under frequent cutting was not as persistent as the ryegrasses. Felopa festulolium was inferior to the perennial ryegrasses and fescues in yield, the distribution of that yield, and persistence. Weeds contributed 1-10% of total yield over 2 years. The experiment suggests that the fescue cultivars are the most productive temperate grasses for perennial irrigated pastures in the subtropics, although better animal performance would improve farmer acceptance. The addition of a ryegrass component to fescue swards increased yields during establishment but did not improve overall yields. Late-maturing cultivars are the highest yielding of the perennial ryegrasses. Rust sensitivity needs improvement as all the present lines are highly susceptible.