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Munn A.J.,University of Wollongong | Munn A.J.,University of South Australia | Munn A.J.,University of New South Wales | Alemseged Y.,Trangie Agricultural Research Center | And 6 more authors.
Rangeland Journal | Year: 2016

Details of the energy (food) requirements of domestic herbivores are essential for predicting grazing pressures and subsequent ecological impacts on rangelands. However, these details are lacking for some of the more recently introduced sheep breeds to Australia, such as the Dorper breed sheep, which are principally meat sheep, and it is uncertain how they compare with the traditional Merino, a wool-breed, sheep. We used the doubly labelled water method to compare the field metabolic rate and water turnover rate of Dorpers and Merinos grazing together in a small holding paddock in a typical rangeland environment. We found no significant differences in field metabolic rate (Dorpers 481 ± 125kJ and Merinos 500 ± 109 kJ kg-0.73 day-1) or water turnover rate (Dorpers 397 ± 57mL and Merinos 428 ± 50 mL kg-0.8 day-1). As such we conclude that under controlled conditions with limited movement and ready access to feed and water, dry sheep equivalent of 1 is appropriate for Dorpers (that is, one Dorper ewe had a grazing requirement equal to one standard, dry Merino wether). However, we also found that the field metabolic rate for Merinos under these conditions was only around half that measured in published studies for animals ranging freely in a large paddock system. This suggests that more work is needed to fully appreciate the energetic and grazing impacts of Dorpers versus Merinos under more realistic grazing conditions (e.g. large paddock systems) where feed and water are more spread. It also highlights limitations of the current dry sheep equivalent rating system, which has been derived from laboratory measures of sheep metabolic rates. © 2016 Australian Rangeland Society.


Melville G.,Trangie Agricultural Research Center | Stone C.,Australian Department of Primary Industries and Fisheries | Turner R.,Remote Census Pty Ltd
New Zealand Journal of Forestry Science | Year: 2015

Background: Precision in describing plantation attributes is a key requirement for forestry managers and inventory surveys aim to extract the most precise information possible using the smallest number of plots. This paper quantifies the potential efficiencies to be gained by using Light Detection and Ranging (LiDAR) data as an aid to estimation of standing timber volume in softwood plantations. A range of inventory design and estimation methods were investigated in terms of their overall predictive efficiency. Methods: Field measurements representing four different populations from two Pinus radiata D. Don plantations in New South Wales, Australia, were used to inform statistical models which were then employed to simulate populations of inventory plots. These plots were then “surveyed” using a variety of simulated sampling strategies to quantify the benefits from using LiDAR data as auxiliary information. Model-based and design-based methods were both investigated. Survey design options included stratification and plot selection strategies; estimation options included ratio estimation and regression modelling. Results were compared in terms of the relative bias and root mean squared error of the estimates. Results: The study suggests that relative efficiencies of two-fold or better, are possible with either model-based or model-assisted estimators compared to traditional inventory surveys which use grid samples and simple design-based estimators. This would enable a halving in the required sample size for the same precision for field inventories in these plantations. Conclusion: The use of LiDAR data as an aid to survey design produces marked efficiency gains compared to traditional inventory methods. © 2015, Melville et al.; licensee Springer.


Melville G.,Trangie Agricultural Research Center | Stone C.,Australian Department of Primary Industries and Fisheries | Rombouts J.,One FortyOne Plantations
Proceedings of Spatial Accuracy 2016 | Year: 2016

The use of airborne laser scanner (ALS) data to estimate forest resource inventory variables is now becoming widespread in Australia (Rombouts et al., 2010; Stone et al., 2011). ALS data is combined with survey plot data to construct model-based estimates of timber volume. In particular, volumes of timber products, sourced from plantations of Pinus radiata have successfully been estimated using nearest neighbor methods. One of the challenges in this approach is to construct samples which capture the full efficiency gains which are achievable using the multiplicity of variables which can be derived from the ALS data. Some of the sampling design approaches that have been investigated include random sampling, grid sampling, stratification, systematic selection and balanced sampling. Estimates have been examined from both a designbased and model-based perspective (Melville et al., 2015). This talk will present results based on several approaches including a novel method specifically designed for imputation which optimizes the survey design by using the distance properties of the sample in the space defined by the auxiliary variables.


Melville G.J.,Trangie Agricultural Research Center | Welsh A.H.,Australian National University | Stone C.,Australian Department of Primary Industries and Fisheries
Journal of Agricultural, Biological, and Environmental Statistics | Year: 2015

This paper explores and develops design-based and model-based methods which are suited to sampling strategies developed for LiDAR-assisted plantation inventories. Much of the model-based theory is either recent or adapted from other areas of sampling. The design-based theory extends and adapts previous work to the present situation. The methodology is developed around the increasing utility and precision of LiDAR as a sampling tool for operational forest inventory. Flexible-radius plots, as a means of optimizing the sampling effort, are examined from a sampling perspective. Mixed models are also employed to model the residual variance using specified correlation structures and this includes predictors which utilize local trend such as those employed in kriging. In the design-based setting, model-assisted estimators are used, including regression and ratio estimators. A plot-based survey of a young, single-aged stand located within a Pinus radiata plantation in the northern tablelands of New South Wales is used to illustrate the theory. Model covariates are obtained from airborne laser scanning (LiDAR) data. © 2015, International Biometric Society.


Khairo S.A.,NSW Trade and Investment | Hacker R.B.,Trangie Agricultural Research Center | Atkinson T.L.,Trangie Agricultural Research Center | Turnbull G.L.,Agriculture NSW
Rangeland Journal | Year: 2013

Feral goats (Capra hircus) are increasing in abundance and distribution in the semi-Arid and arid rangelands of New South Wales, and elsewhere in the southern rangelands. They present a conundrum for natural resource managers and policy-makers as they can be both an agricultural and environmental pest and an economic resource for landholders. This paper presents an economic analysis of a range of alternative approaches to feral goat management and assesses their implications for natural resource management policies. 'Opportunistic harvesting' and 'value-Added' strategies (the latter involving use of a paddock to increase the liveweight of feral goats before slaughter for meat) returned positive net benefits to landholders, whereas the strategy of 'no management' resulted in a negative net benefit if the overall stocking rate was held constant. The erection of goat-proof boundary fencing to enhance production from domestic livestock generated negative net benefits unless increases in stocking rates of domestic livestock could be achieved within the exclusion fencing through improved grazing management. The use of goat-proof fencing to establish an individual paddock for domestic livestock production returned positive net benefit for landholders but also required increases in domestic stocking rate to be competitive with the best feral goat harvesting strategy. The 'opportunistic harvesting' and 'value added' strategies are thus likely to be adopted by producers without financial incentive and could result in positive resource conservation outcomes if goat prices encourage harvesting. The 'no management' strategy will most likely promote resource degradation and should be discouraged. Strategies involving goat-proof fencing are likely to provide positive net benefits for landholders and achieve positive natural resource outcomes if associated with improved grazing management, and reduced density of feral goats outside the exclusion fencing. It is concluded that resource conservation benefits of feral goat control strategies may be positive, negative, or neutral depending on the management strategy adopted, the extent of goat-proof fencing, and the price of meat from feral goats. It is, therefore, difficult to rely on the commercial harvesting of feral goats to achieve resource conservation objectives. Public funds could be better used to support education and training in grazing management and provide incentives for achievement of measurable natural resource outcomes than to support infrastructure establishment for the harvesting of feral goats on private properties.


Neal J.S.,Elizabeth Macarthur Agricultural Institute | Neal J.S.,University of Sydney | Fulkerson W.J.,University of Sydney | Hacker R.B.,Trangie Agricultural Research Center
Agricultural Water Management | Year: 2011

The increasing cost and scarcity of water for irrigation is placing pressure on Australian dairy farmers to utilize water more efficiently, and as result, water use efficiency (WUE) of forages is becoming an important criterion for sustainable dairy production. This study was conducted to identify more water use efficient forage species than the dominant dairy forage, perennial ryegrass (Lolium perenne L.). Seventeen annual forage species were investigated under optimum irrigation (I1) and two deficit irrigation treatments (nominally 66 and 33% of irrigation water applied to the optimal level), over 3 years at Camden, NSW, on a brown Dermsol in a warm temperate climate. Forages with the highest yield generally had the highest WUEt (total yield/evapotranspiration). Under optimal irrigation, there was a three-fold difference in mean annual WUEt between forages, with maize (Zea mays L.) having the highest (42.9kgha-1mm-1) and cowpea (Vigna unguiculata (L.) Walp.) the lowest (13.5kgha-1mm-1), with 11 of the forage species having a greater WUEt than perennial ryegrass. The 'harvested' forages maize, wheat, triticale (Triticosecale rimpaui Wittm.) and maple pea (Pisum sativium L.) generally had higher mean WUEt (26.7-42.9kgha-1mm-1) than the remaining forages which were defoliated multiple times to simulate grazing (13.5-30.1kgha-1mm-1). The reduction in annual WUEt in response to deficit irrigation was greatest for the warm season forages with up to 30% reduction for maize, while most of the cool season annuals were not significantly affected by deficit irrigation at the levels imposed. In order to maximize WUEt of any forage, it is necessary to maximize yield, as there is a strong positive relationship between yield and WUEt. However, while WUEt is an important criterion for choosing dairy forages, it is only one factor in a complex system. Choice of forages must be considered on a whole farm basis and include consideration of yield, nutritive value, cost of production and risk. © 2010.


Hacker R.B.,Trangie Agricultural Research Center | Jessop P.J.,Dareton Research and Advisory Station | Smith W.J.,Trangie Agricultural Research Center | Melville G.J.,Trangie Agricultural Research Center
Rangeland Journal | Year: 2010

Inconsistencies can commonly be expected between the financial goals of rangeland grazing enterprises and public conservation goals such as maintenance of ground cover to reduce erosion. Where the State wishes to promote conservation outcomes, incentive schemes which reward these outcomes on privately managed grazing lands are an option. We describe one such scheme intended to achieve conservation outcomes and support the development of resilience in the complex adaptive (humanenvironmental) rangeland system through payments related to measured ground cover. A pilot program in western New South Wales has shown that the practical operation of such a program is uncomplicated and that while several theoretical issues could be further refined there is a rationale for extension of the program based on parameters and processes that are agreed by the participants. We suggest that development of such a scheme should be considered as part of the policy mix related to natural resource management and drought assistance. © 2010 Australian Rangeland Society.


Alemseged Y.,Trangie Agricultural Research Center | Hacker R.B.,Trangie Agricultural Research Center | Smith W.J.,Trangie Agricultural Research Center | Melville G.J.,Trangie Agricultural Research Center
Rangeland Journal | Year: 2011

Thickening of native shrubs is a major problem in many 'semi-arid woodlands' as significant increase in shrub density is often negatively correlated with herbaceous vegetation and leads to reduced pasture production and soil erosion. This project aimed to test the hypothesis that temporary cropping (up to three crops in 15 years) consistently increases the density of native perennial grasses following the removal of shrubs. A total of 30 paddocks that had been cropped during the last 20 years were randomly selected using a satellite-based database that documented annual clearing and cropping history from 1987 to 2003. Paddocks were classified into four types based on clearing and cropping history and grazing management not cleared (shrubs), regrowth (re-invaded by shrubs), set stocked (cropped and grazed), light/rotationally grazed (cropped and grazed). The responses of vegetation and soil (chemical and physical) properties to clearing and cropping were evaluated. Results indicated that ground cover, native perennial grass cover and standing dry matter were highest under light/rotationally grazed conditions. The shrub state represents a stable state within the Cobar pediplain brought about due to land-use change in the form of overgrazing and/or the removal of fire from the system. An alternative stable state was achieved as a result of disturbance in the form of clearing, cropping and grazing management thereby directly altering the shrub population. The resilience of this state is largely dependent on the grazing management system used and on the prevention of shrub from re-establishing while failure to control shrubs could lead to the re-emergence of the Shrub State. We conclude that native grasslands do regenerate following cropping after removal of shrubs. The importance of grazing management for restoring perennial ground cover following removal of shrubs and temporary cropping has been clearly demonstrated by the study. © 2011 Australian Rangeland Society.

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