Performance of 7 Australian native grasses from the temperate zone under a range of cutting and fertiliser regimes

Abstract

This glasshouse study aimed to examine the performance of 7 Australian native grasses and their responses to different cutting and fertiliser regimes. The 7 native grasses comprised 2 wallaby grasses (Austrodanthonia bipartita cv. Bunderra and Austrodanthonia setacea, Woodhouse ecotype), 2 weeping grasses (Microlaena stipoides cv. Bremmer and ecotype Coleraine), 1 spear grass (Austrostipa mollis, ecotype Lexton), 1 red-leg grass (Bothriochlora macra, ecotype Hamilton), and 1 kangaroo grass (Themeda triandra, ecotype Yass). For each of the 7 grasses, 64 pots each containing 9 plants were arranged in a 4 cutting intensity × 4 fertiliser level factorial design with 4 replicates. The cutting intensity treatments involved (1) cutting to 2 cm at 3–5-week intervals; (2) cutting to 5 cm at 3–5-week intervals; (3) cutting to 10 cm at 3–5-week intervals; and (4) cutting to 2 cm based on leaf stage. The fertiliser regimes included low, medium, and high fertility treatments by applying various rates of phosphorus, and the treatment with addition of compost tea. Herbage accumulation, shoot and root growth, plant survival and tiller density, nutritive characteristics, and leaf stage were monitored. All grass lines produced the lowest herbage mass when cut to 2 cm above ground at 3–5-week intervals. Cutting to 5 cm or to 2 cm based on leaf stage favoured herbage accumulation of Lexton spear grass, Hamilton red grass, Yass kangaroo grass, and Coleraine weeping grass. Cutting to 10 cm favoured herbage accumulation of Bremmer weeping grass and wallaby grass. Cutting to 10 cm together with high fertiliser application considerably increased herbage accumulation in comparison with treatments with low fertiliser application or with compost tea. Shoot and root biomass were maximised when plants were cut to 10 cm above ground, except Lexton spear grass which had highest root biomass when plants were managed based on leaf stage. Plant survival was dramatically affected by defoliation intensity and varied among species. Plant survival declined when plants were cut to 2 cm above ground for most species. Overall, native grasses were considered to have good nutritive characteristics with crude protein ranging from 17 to 22% and neutral detergent fibre from 48 to 60%. Results from this study indicate that it may be possible to use leaf stage as a determinant for the commencement of grazing native species. Optimum leaf stages that could be used as a grazing management guide were on average 3.4 for wallaby grass, 4.2 for weeping grass, 3 for spear grass, 3.8 for red-leg grass, and 4.4 for kangaroo grass. However, further work is required to better define this for likely seasonal variation between C3 and C4 species.