Crop and Pasture Science Crop and Pasture Science Society
Plant sciences, sustainable farming systems and food quality
RESEARCH ARTICLE

Impacts of grazing management options on pasture and animal productivity in a Heteropogon contortus (black speargrass) pasture in central Queensland. 1. Pasture yield and composition

D. M. Orr A E , W. H. Burrows A D , R. E. Hendricksen A D , R. L. Clem B , P. V. Back A D , M. T. Rutherford A , D. J. Myles A D and M. J. Conway C
+ Author Affiliations
- Author Affiliations

A Department of Employment, Economic Development and Innovation, PO Box 6014, Rockhampton Mail Centre, Qld 4702, Australia.

B Department of Employment, Economic Development and Innovation, PO Box 395, Gympie, Qld 4625, Australia.

C Department of Employment, Economic Development and Innovation, Locked Mail Bag 6, Emerald, Qld 4720, Australia.

D Retired.

E Corresponding author. Email: david.orr@deedi.qld.gov.au

Crop and Pasture Science 61(2) 170-181 https://doi.org/10.1071/CP09193
Submitted: 3 July 2009  Accepted: 9 December 2009   Published: 8 February 2010

Abstract

An extensive grazing study was conducted between 1988 and 2001 in a Heteropogon contortus (black speargrass) pasture in central Queensland. The study was designed to measure the effects of stocking rate on native pasture, native pasture with legume oversown, and native pasture with animal diet supplement/spring burning on pasture and animal production. Summer rainfall throughout the study was below the long-term mean. Mean annual pasture utilisation ranged from 13% at 8 ha/steer up to 61% at 2 ha/steer. Increasing stocking rate treatments reduced total pasture yields while total yields in legume oversown treatments were similar to those in native pasture at the same stocking rate. When spring burning was possible, total yields were reduced in the subsequent autumn. Increasing stocking rate in native pasture tended to reduce H. contortus and Bothriochloa bladhii, increased the composition of intermediate species, such as B. decipiens and Chloris divaricata, and also changed the frequencies of a range of minor species. Oversowing legumes resulted in Stylosanthes scabra cv. Seca increasing from <1% of pasture composition in 1988 to 50% in 2000 and was associated with a reduction in H. contortus and changes in the frequencies of some minor species. Stocking rates heavier than 4 ha/steer resulted in annual pasture utilisation greater than 30% and were unsustainable because they reduced total yield and resulted in undesirable changes in species composition. It was concluded that pasture production was sustainable when stocking rates were maintained at 4 ha/steer, which equates to 30% annual pasture utilisation, and through the judicious use of spring burning.

Additional keywords: species composition, stocking rate, legume oversowing, burning, Heteropogon contortus pastures.


Acknowledgments

Special acknowledgment is made to the Neill-Ballantine family (Galloway Plains Pastoral Co.) for their ready co-operation and for the long-term use of land on which the study was based. Many people contributed to the overall conduct of this grazing study during its 13-year duration and it is impossible to comprehensively list all these people here. We especially thank the large number of Department of Primary Industries and Fisheries and Department of Natural Resources and Water staff who made major contributions to this study’s success. A Producer Advisory Group readily gave constructive advice throughout the study. Funding was provided by Meat and Livestock Australia.


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