Effects of stocking rate, legume augmentation, supplements and fire on animal production and stability of native pastures

Summary

Objective (1).

Assess the productivity and stability of native pastures grazed at a range of stocking rates, with or without the addition of legumes and fire. This objective was fully achieved. The grazing study clearly established that cattle production is sustainable when native pasture is grazed continuously at 4 ha/steer which equates to 30% pasture utilisation. Increasing stocking rate to 3 or 2 ha/steer increased pasture utilisation beyond 30% and became increasingly unsustainable. This was indicated by reduced total pasture yield, reduced occurrence of desirable perennial grasses, increased occurrence of intermediate grasses and changes in the occurrence of a range of minor species. Oversowing legumes into native pasture resulted in a substantial increase in the contribution of legume to total pasture yield, reduced the contribution of H. contortus and changed the occurrence of a range of minor species. Spring burning increased the occurrence of H. contortus but only at light stocking rates. Animal production per head was greatest at the lightest stocking rate but declined with increasing stocking rate. Animal production per hectare was highest at the heaviest stocking rate and decreased with increasingly light stocking rate. Oversowing legumes substantially increased animal liveweight gain over native pasture at the same stocking rate. Burning had a variable impact on animal production compared with native pasture. Animal diet studies using oesophageal fistulated steers indicated that cattle preferentially grazed H. contortus when it was available in the pasture. Cattle also selected Chrysopogon fallax, Seca stylo, forbs and sedge species when they were available in the pasture. Cattle seldom preferred Bothriochloa bladhii despite the fact that this species often comprised around 50% of the pasture yield.

Objective (2).

Use the results recorded between 1988 and 1996 to demonstrate to producer groups that lenient grazing together with other pasture technologies can be both ecological and economically viable. Throughout the duration of the grazing study, large numbers of individual producers and LandCare groups visited the site. Field days were conducted for a number of regional groups including Calliope, Miriam Vale, Marlborough and Mornish LandCare groups. The Mornish and Marlborough LandCare group visits were particularly successful as both groups travelled to and from the site by bus with lively discussion on the return trips following the results presented during their visits. A final Galloway Plains field day was held at Galloway Plains on 10 May 2001 with over 200 producers attending. A number of the producer present had attended earlier field days and discussion days and had returned to seek further information. A producer friendly booklet of the Galloway Plains grazing study entitled 'Sustainable cattle production from Black Speargrass pastures in central Queensland' is at an advanced stage of preparation. This booklet details the results from the grazing study and presents practical guidelines for the sustainable grazing management of H. contortus pastures in central Queensland. Results from Galloway Plains grazing study are being incorporated into the Grazing Land Management Education Package. The DPI&F staff who were responsible for the conduct of the Galloway Plains grazing study are actively assisting Grazing Land Management Education staff in central Queensland to tailor the package for the Fitzroy Basin.

Objective (3).

Promote basic pasture science and monitoring techniques so that producers can better recognise ecological processes. This objective was achieved through a series of field and discussion days conducted with local producers and LandCare groups. This objective was achieved through a Producer Advisory group which was selected to represent a range of producers, scientist and extension staff throughout central Queensland. This Producer Advisory Group met twice per year between 1998 and June 2001 and challenged the Galloway Plains research team in a wide range of sustainability and production issues. For example, the theme of what was the right balance of grass: stylo and how to maintain that balance was a recurring issue. This issue was the focus of further research including the Strathmuir Producer Demonstration Site (1997-2001) and subsequent Belmont stylo management study (2000-current). Results from Galloway Plains grazing study are being incorporated into the Grazing Land Management Education Package. The DPI&F staff who were responsible for the conduct of the Galloway Plains grazing study are actively assisting Grazing Land Management Education staff in central Queensland to tailor the package for the Fitzroy Basin.

Objective (4).

Conduct comprehensive economic analyses of animal production from all pasture treatments including the application of the results to commercial case studies. A designated economist will be appointed by 31-12-1997 pending the Beef Institute restructuring. This objective was not achieved. A designated economist was not appointed to conduct the comprehensive economic analyses of animal production. Nevertheless, a detailed economic analysis was conducted and this analysis reinforced the conclusions supporting a stocking rate of 4 ha/steer. Any economic advantage achieved by stocking at 3 or 2 ha/steer dissipated with time as the impact of this heavy grazing resulted in deleterious changes in the condition of the soil and pasture resources. In turn, this decline in soil and pasture condition resulted in reduced animal liveweight performance.

Objective (5).

Incorporate results from this study using GRASP to determine optimum stocking rate and economic performance for commercial beef enterprises in the black speargrass region. This objective has not been met within the current project. However, the Galloway Plains data is being incorporated in GRASP calibration and modelling research being undertaken as part of the MLA funded modelling project NBP.338 Improving grazing management using the GRASP model.

Objective (6).

Promote the results from this study and encourage adoption of optimum stock management strategies as outlined in the draft communication strategy. Staff involved with the Galloway Plains grazing study have actively promoted the results throughout the duration of the study and encouraged the adoption of sustainable grazing management practices. Major field days were conducted at approximately 3 year intervals and these days were well attended by regional producers from Marlborough / St Laurence in the north to Miriam Vale / Gin Gin in the south.