Herbage accumulation, soil seed reserve and nutritive value under different grazing and fertiliser regimes in a hill pasture in southern Australia
Developing sustainable grazing management systems for steep hill country is critical to protect the land from degrading due to soil and wind erosion, salinity and loss of biodiversity. Systems that increase the ground cover by perennial species can also improve pasture production, the seasonal distribution of feed supply and nutritive value of pastures. A field study was carried out in western Victoria, Australia from 2002 to 2006, to identify the impacts of deferred grazing, no defoliation of pastures for a period generally from spring to autumn, and fertiliser application on herbage accumulation, soil seed reserve and nutritive value in a hill pasture consisting of 23% of Australian native grasses, 10% of exotic perennial grass and 77% of other species (predominantly annual grasses). The soil was a sedimentary clay loam, with pHCaC12 5.2 and Olsen P 4 mg/kg. The long-term average rainfall (LTA) was 590 mm recorded since 1969; however, annual rainfall was considerably lower than the long-term average during the course of the experiment (<500 mm for most of the years). Three deferred grazing strategies -short-term deferred grazing (no defoliation between October and January each year), long-term deferred grazing (no defoliation from October to the autumn break each year) and optimised deferred grazing (withholding time from grazing depends on morphological development of the plants), and 2 fertiliser levels (no fertiliser applied and single superphosphate at 50 kg P/ha plus lime at 2000 kg/ha applied in 2002) were used to form 6 treatments in a factorial (2× 3) arrangement. These treatments were allocated with 2 additional treatments in a randomised block design with 3 replicates. The 2 additional treatments included one without grazing in year 1 and one grazed continuously (control). Deferred grazing increased (P < 0.05) herbage accumulation. On average, deferred grazing produced 4.5 t DM/ha/year (ranging from 3.8 to 4.91 DM/ha/year), 40% higher than the control (3.21 DM/ha/year). Among the deferred grazing treatments, the mean herbage accumulation for the short-term deferred grazing and optimised deferred grazing treatments were 4.61 DM/ha/year, 11% higher than the long-term deferred grazing. The treatment fallowed (no grazing) in year 1 produced 4.3 t DM/ha/year, 35% higher than the control. Application of fertiliser increased (P < 0.05) the herbage accumulation by 15% in comparison to the control. Averaged over 4 years, deferred grazing increased (P < 0.05) the soil seed reserve of perennial grasses by 200%, and annual grasses (except optimised deferred grazing) by 50% compared with the control (220 seeds/m2 for perennials and 1910 seeds/m2 for annuals). Optimised deferred grazing decreased the soil seed reserve of annual grasses by 50%. Averaged over 4 seasons, deferred grazing increased (P < 0.01) the dry matter digestibility of pastures by 8%, but did not affect (P>0.05) crude protein and neutral detergent fibre, compared with the control. Low-input management systems are often implemented in steep hill country, which imposes environmental risks due to overgrazing, and lack of weed and pest control. Deferred grazing, which can be applied in large scale at low cost, provides an effective tool in lifting pasture DM yield and nutritive value and enhancing environmental sustainability, through improvement in native species groundcover and reduction in annual weed population.
Z.N.Nie R.P.Zollinger
Department of Primary Industries, Private Bag 105, Hamilton, VIC 3300, Australia
国际会议
The Workshop of Sustainable Grassland Management in China and Australia(中国--澳大利亚可持续性草地管理研讨会)
乌鲁木齐
英文
75
2011-08-01（万方平台首次上网日期，不代表论文的发表时间）