| dc.description.abstract |
Four pasture treatments were compared with a perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) mixture, the commonly sown pasture type, at 3 sites in south-western Victoria, to determine the extent to which total annual herbage accumulation and seasonal growth pattern could be manipulated in non-irrigated dairy systems. The pasture treatments were: (1) short-term winter-active (STW), based on Italian ryegrass (Lolium multiflorum); (2) long-term winter-active (LTW), based on Mediterranean tall fescue (Festuca arundinaceae) or cool-season active perennial ryegrass; (3) long-term summer-active (LTS), based on Continental tall fescue; and (4) perennial ryegrass pasture receiving moderately high nitrogen (N) inputs in winter and spring (total of 210�kg�N/ha.year) to increase herbage accumulation during the ryegrass growing season (RHN). The perennial ryegrass and white clover mixture served as the control treatment. The 3 sites were Heytesbury (heavy clay soil), Terang (duplex soil), and Naringal (light soil). All pasture treatments were grazed by dairy cows. Herbage accumulation rate, botanical composition, and nutritive value of all pasture treatments were measured for 3 years. The winter-active pasture types had little effect on the overall seasonal distribution of forage supply or total annual yield compared with the control treatment. By contrast, the long-term summer-active pasture type significantly increased herbage accumulation during summer compared with all other pasture types (mean of an additional 1.3�t�DM/ha during summer compared with the control treatment across all sites and years). However, this came at the cost of lower winter production (mean 0.8�t�DM/ha). The LTS pasture also produced less dry matter than all other treatments in the first year after sowing at 2 of the 3 sites, reflecting the slower establishment of tall fescue. Ryegrass receiving high N inputs grew more total herbage on an annual basis than LTS. Mean total annual herbage accumulation (kg�DM/ha.year) over the 3 years and 3 sites was in the order: RHN (14400)�>�LTS (13760)�=�Control (13170)�>�STW (12450)�=�LTW (12170) (P�<�0.01). The results demonstrated that improvements over the industry ?standard' perennial ryegrass/white clover pasture management system in total herbage accumulation and the seasonal pattern of pasture growth are possible using existing pasture technology (mixtures of different species and cultivars, and N fertiliser inputs). However, significant interactions among sites, years and pasture treatments for several variables reinforced the need to understand limitations to plant growth on a site-by-site basis, to select plants that match the environmental conditions, and to then manage them appropriately to reach their growth potential. |
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