Enhancing profits from poplar box country by tactical pasture management
Silcock, R.G. Dr; Ph: (07) 4631 4263; Fax: (07) 4634 7421; silcocr@dpi.qld.gov.au
Hall, T.J. Mr; Ph: (07) 4622 3930; Fax: (07) 4622 4824
Jordan, D.J. Mr; Ph: (07) 4622 1511; Fax: (07) 4622 3235
Research organisations: Queensland Department of Primary Industries, Sheep and Grazing Game Subprogram, PO Box 102, Toowoomba Qld 4350
Queensland Department of Primary Industries, Sheep and Grazing Game Subprogram, PO Box 308, Roma Qld 4455
Sponsors: AWRAPO: Australian Wool Research and Promotion Organisation
Objectives:
1. To quantify the economic cost to producers of a high proportion of undesirable grass species in native pasture, especially wiregrasses and Eragrostis species;
2. To understand life cycles and defoliation tolerance of the desirable and undesirable key species sufficiently to formulate decisive management principles for perennial grass pastures;
3. To formulate management strategies for future grazing experiments designed to develop practical ways of achieving better pasture composition and consequently better economic returns for wool growers.
Methodology:
1. Graze 20ha areas in adjacent paddocks with very different pasture condition at two sites to quantify production and wool quality differences in wool growth, fibre diameter, vegetable fault. Quantify the quality of these pastures at different times via sampling, sorting and in vitro analysis;
2. Study key species for their seedling regeneration capacity and persistence in pastures under moist and drought conditions. Impose management systems to encourage or weaken key grasses, eg by burning, crash grazing, spelling and blade ploughing;
3. Discuss with industry, extension officers and researchers in New South Wales and western Queensland the way to put this information into practical management tactics for manipulating pasture to a desirable composition.
Progress:
Most perennial grasses in south Queensland have a wide range of flowering times except black speargrass, rough speargrass and golden beardgrass. Wiregrasses germinate less at higher temperatures and temperature has a large effect on rate of emergence in the field. Ephemerals, forbs, sedges and grasses with small naked seeds, eg. lovegrasses and dropseed grasses, have large, persistent seedbanks which dominate seedling populations after a drought. In contrast, many valuable perennial grasses such as forest bluegrass, mulga mitchell grass and Queensland bluegrass have relatively short-lived seed banks.
Perennial grasses with transient seedbanks depend upon setting seed and then germinating within 18 months. They need two consecutive good summers to fully rejuvenate after a drought. Fortunately most wiregrasses also have short-lived seeds, and few are still viable at the end of a long drought. Shrubs and trees tend to have transient seedbanks, but herb legumes have small, very persistent banks.
Recruitment potential of over 20 native species is summarised. We also provide detailed data on the forage value of many native species at different growth stages.
Wool value from wiregrass-dominated buffel pastures on a red earth was reduced by 5-10% at Roma in 1994/95. Winters in those years were very dry and grass seed problems minimal. Wool from the wiregrass-dominated pastures was significantly finer but of weaker strength. However lighter fleeces and higher skirting rates usually counteracted this price advantage. Wool quality reductions were greater at high stocking rates and patch grazing was a management problem in all pastures.
Tall Jericho wiregrass ( A. jerichoensis var. subspinulifera ) must be defoliated to below 8cm to significantly reduce its seeding potential. Sheep normally avoid the plant, but fire may be an alternative when the plants are very dry. Opportunities to use fire are limited because wiregrass has little leaf and its stems stay quite green for much of winter and freshen up rapidly after spring rains. Wiregrass crowns are readily uprooted or damaged but crowns of desirable grass species such as buffel and Queensland bluegrass are relatively resistant. Thus a light ploughing or blade ploughing may suppress wiregrasses in a mixed pasture.
Period: starting date 1992-07; completion date 1996-04
Status: completed
Keywords: pastures; grazing; grasses; weed control; wool; Aristida; perennials; sheep
Publications:
Silcock, R.G. and Hall, T.J. (1996). Tactical Pasture Management: Enhancing profits from poplar box country. Queensland Department of Primary Industries Project Report QO96007, pp. 41.
Hall, T.J., Silcock, R.G., Sevil, J.J. and Van der Meulen, J.R. (1997). Improving pasture composition increases wool returns in eucalypt woodlands. Proceedings of the 18th International Grassland Congress, Canada. Vol. 3 (in press).
