Optimal management of annual ryegrass (Lolium rigidum Gaud.) in phase rotations in the Western Australian Wheatbelt*

Lucerne (Medicago sativa L.) helps to prevent soil salinisation in the Western Australian Wheatbelt by reducing recharge to saline water tables. There is broad consensus, though, that it is not sufficiently profitable to motivate producers to plant it at the intensity at which considerable off‐site benefits would be conferred. This paper employs a multiple‐phase optimal control model to explore the value of this perennial pasture for the management of herbicide‐resistant annual ryegrass (Lolium rigidum Gaud.) in a crop–pasture rotation, given the difficulty of observing this value in practice. The availability of selective herbicides for efficient weed control is found to determine whether or not it is profitable to adopt lucerne pasture under optimal management. Herbicide resistance requires producers to employ costly, non‐selective treatments for in‐crop weed control. Thus, it motivates the adoption of perennial pasture in which cost‐effective forms of control can be implemented. Moreover, this result is robust to feasible changes in the current economic environment.     

Economic contribution of French serradella (Ornithopus sativus Brot.) pasture to integrated weed management in Western Australian mixed‐farming systems: an application of compressed annealing*

Sowing phases of French serradella (Ornithopus sativus Brot.) pasture between extended cropping sequences in the Western Australian wheatbelt can sustain grain production through restoring soil fertility and reducing selective herbicide use. The objective of this article is to investigate the profitability of rotations involving this pasture under a variety of weed management scenarios to obtain greater insight into its value for mixed farming systems in this region. A stochastic search procedure, compressed annealing, is used to identify profitable sets of weed management strategies in a simulation model representing a large number of potential combinations of chemical and non‐chemical forms of weed control. In contrast to a continuous‐cropping sequence, the inclusion of a serradella phase in a rotation is profitable at high weed densities and with increasing levels of herbicide resistance. A single year of pasture in the rotation is optimal if resistance to Group A selective herbicides is present at the beginning of the planning horizon, but a three‐year phase is required if resistance to multiple herbicide groups is observed. Sowing a serradella pasture twice over a two‐year phase is also shown to be economically attractive given benefits of successive high weed kills.     

Potential of woody biomass production for motivating widespread natural resource management under climate change

In this study we assessed the potential of woody biomass (short-rotation Mallee Eucalypts) for renewable energy generation as an economically viable way of motivating widespread natural resource management under climate change in the 11.9 million ha Lower Murray agricultural region in southern Australia. The spatial distribution of productivity of agricultural crops and pasture, and biomass was modelled. Average annual economic returns were calculated under historical mean (baseline) climate and three climate change scenarios. Economically viable areas of biomass production were identified where the profitability of biomass is greater than the profitability of agriculture under each scenario for three factory gate biomass prices. The benefits of biomass production for dryland salinisation, wind erosion, and carbon emissions reduction through biomass-based renewable energy production were also modelled. Depending on climate scenario, at the median price assessed ($40/tonne) biomass production can generate $51.4–$88 M in annual net economic returns, address 41,226–165,577 ha at high risk of dryland salinisation and 228,000–1.4 million ha at high risk of wind erosion, and mitigate 10.4–12 million tonnes of carbon (CO₂^−e) emissions annually. Economically viable areas for biomass production expanded under climatic warming and drying especially in more marginal agricultural land. Under the baseline, the area at high risk of dryland salinisation was more than double that at high risk of wind erosion. However, under climatic warming and drying the relative importance of these two natural resource management objectives switched with the area at high risk of wind erosion becoming much larger. As biomass production can achieve multiple natural resource management objectives, it may provide a land use policy option that is adaptable to changing priorities and economically resilient given climatic uncertainties. For such a significant and enduring land use change policy it is prudent to assess both the economic and environmental potential under climate change.     

Is Australia on a sustainability path? Interpreting the clues*

Genuine savings is a conceptually valid one‐sided indicator as to whether Australia is on a weak sustainability path (negative GS would warn that current welfare is unsustainable). The World Bank's adjusted net savings (ANS) data summarise the available evidence, and by this indicator Australia is muddling along, at best. ANS misses some important pieces of the picture – net depletion of water, soil and biodiversity, and most kinds of pollution damage – and thus overstates Australia's genuine savings performance. Weak sustainability can be promoted by getting the prices right, and piecemeal efforts are underway via regulatory approaches and resource/environmental markets of various kinds. Nevertheless, particular resource problems – habitat conservation, biodiversity, climate change and dryland salinity – are likely to also require strong sustainability approaches. A sustainable future involves pushing weak sustainability as far as the body politic permits, invoking precautionary instruments for specific resource crises, and nurturing policy processes that encourage the consensus‐building that will be necessary to get it done.     

Climate Change and the Economics of Farm Management in the Face of Land Degradation: Dryland Salinity in Western Australia

Projected changes in climate would affect not only the profitability of agriculture, but also the way it is managed, including the way issues of land conservation are managed. This study provides a detailed analysis of these effects for an extensive dryland farming system in south-west Australia. Using a whole-farm linear programming model, with discrete stochastic programming to represent climate risk, we explore the consequences of several climate scenarios. Climate change may reduce farm profitability in the study region by 50% or more compared to historical climate. Results suggest a decline in the area of crop on farms, due to greater probability of poor seasons and lower probability of very good seasons. The reduced profitability of farms would likely affect the capacity of farmers to adopt some practices that have been recommended to farmers to prevent land degradation through dryland salinization. In particular, establishment of perennial pastures (lucerne or alfalfa, Medicago sativa ), woody perennials ("oil mallees", Eucalyptus spp.), and salt-tolerant shrubs for grazing ("saltland pastures", Atriplex spp.) may become slightly more attractive in the long run (i.e., relative to other enterprises) but harder to adopt due to their high establishment costs in the context of lower disposable income.     

From weed to wealth? Prospects for medic pastures in the Mediterranean farming system of north-west Syria

Medic (Medicago spp.) pastures are widely grown in rotation with dryland cereal crops in Mediterranean climate zones of Australia. Attempts since the 1960's to introduce this system to Mediterranean west Asia and north Africa (the native region of medic) have not lead to significant adoption; farmers in the region recognize medic, but as a weed and natural pasture plant. This first detailed economic evaluation of the rotational medic system was conducted using a whole-farm linear programming model based on the agricultural system of north-west Syria. The model represents in detail impacts of rotation on yields, labor requirements of alternative farm activities, availability of family and hired labor, subsistence income requirements, livestock feed sources and uses at different times and a choice of sheep stocking rates. Biological data for the analysis are based on a large six-year cropping and grazing experiment near Aleppo on terra-rossa soil with rainfall mainly in winter and averaging about 330 mm annually. The trial compared a dryland medic-wheat system and traditional two-year rotations of wheat with: fallow, watermelon, lentil and vetch. Results indicate that, given current prices and yields from the trial, medic is less profitable than traditional rotations. The model was used to investigate situations in which medic would be economically preferred. Selection of a medic rotation by the model was found to be particularly sensitive to the area of the farm and the price of labor. On small farms, labor availability per hectare is high, favouring the production of labor intensive crops such as lentil and watermelon. On larger farms, labor costs of these enterprises are substantial, increasing the relative profitability of medic, especially if labor prices increase. Interestingly, the relative desirability of medic is more sensitive to its impact on subsequent wheat crops than to the level of pasture production. We also found that modest increases in the prices of sheep products (especially milk) have a major impact on the economic performance of medic. These insights will allow improved focusing and targeting of future research and extension activities.     

Economic benefits of public investment in weed management: the case of vulpia in south-eastern Australia's temperate pasture areas

The present paper reports an economic evaluation of the long-term benefits to Australia of research by the Cooperative Research Centre for Weed Management Systems (CRC) into the improved management of vulpia , the major annual grass weed of temperate pastures in New South Wales and Victoria. Vulpia reduces livestock production by competition with more desirable pasture species, by the production of low quality feed at critical times of the grazing cycle, and by injury to animals. A 20-year stochastic benefit-cost analysis indicated that reducing the impacts of vulpia in these pastures produced a mean net present value of $A58.3 million and a mean benefit-cost ratio of 33:1. Temperate pasture zone wool producers would capture the largest shares of these benefits, Australian consumers would gain, but wool producers in the rest of Australia would suffer welfare losses from vulpia reductions in the temperate pasture zones.     

Assessing the returns to R&D on perennial crops: the costs and benefits of Pierce's disease research in the California winegrape industry

Several complicating issues arise in evaluating the returns to research into varietal improvements for perennial crops compared with annual crops. We elucidate and address these issues in the context of a case study of research aiming to develop varieties that are resistant to Pierce's disease (PD) of grapevines. PD imposes costs of over $100 million per year on the California grape industry, even with public PD control programs in place. Research projects to develop PD resistant varieties of grapevines are at various stages of completion. We describe the economic problems posed by PD, document the research programs undertaken to address the disease and present an economic assessment of the returns to the investment, which are conditional on other policies. Using a simulation model of the market for California winegrapes, we estimate the benefits from research, development and adoption of PD‐resistant vines as ranging from $4 million to $129 million annually over a 50‐year horizon, depending on the length of the R&D lag and the rate of adoption. In addition to these specific quantitative results the paper offers insight into the broader question of economic evaluation of damage‐mitigation technology for perennial crops.     

The external costs of pasture weed spread: an economic assessment of serrated tussock control

The external cost associated with the spread of pasture weeds such as serrated tussock (Nassella trichotoma) is an important economic problem. This problem is complicated in many parts of south‐eastern Australia where low rainfall and low soil fertility prevent the economic viability of control of this weed through pasture improvement. A consequence of serrated tussock spread in this region has been calls for increased public intervention in its control. However, because there have been no attempts to measure the external costs of serrated tussock spread, one of the major economic grounds on which this activity might be justified has not been quantified. The purpose of this paper is to provide this information. A stochastic simulation model is developed to determine the size of the external cost associated with the spread of serrated tussock and to evaluate the economic benefits of a range of control scenarios. It is concluded that on low rainfall‐low soil fertility country the socially optimal control option for serrated tussock is to retire land from agriculture and re‐vegetate it with trees.     

An assessment of the economic and environmental potential of biomass production in an agricultural region

The establishment of deep-rooted perennial species and their processing for biomass-based products such as renewable energy can have benefits for both local and global scale environmental objectives. In this study, we assess the potential economic viability of biomass production in the South Australian River Murray Corridor and quantify the resultant benefits for local and global scale environmental objectives. We model the spatial distribution of economically viable biomass production in a Geographic Information System and quantify the model sensitivity and uncertainty using Monte Carlo analysis. The total potentially viable area for biomass production under the Most Likely Scenario is 360,728 ha (57.7% of the dryland agricultural area), producing over 3 million tonnes of green biomass per annum, with a total Net Present Value over 100 years of A$ 88 million. The salinity in the River Murray could be reduced by 2.65 EC (μS/cm) over a 100-year timeframe, and over 96,000 ha of land with high wind erosion potential could be stabilised over a much shorter period. With sufficient generating capacity, our Most Likely Scenario suggests that economically viable biomass production could reduce carbon emissions by over 1.7 million tonnes per annum through the production of renewable energy and a reduced reliance on coal-based electricity generation. Our analyses suggest that biomass production is a potentially viable alternative agricultural system that can have substantial local scale environmental benefits with complimentary global scale benefits for climate change mitigation.     

Investing in Perennial Pasture Improvement: A Real Options Analysis

In investment analysis, uncertainty and irreversibility can undermine net present value (NPV) as a decision rule since the option to delay investment may have value. We apply the real option theory of investment to the pasture investment decision facing livestock producers in southwest Western Australia. In 2006, livestock producers thinned their herds as pasture availability dwindled due to extreme drought conditions. This left producers with a unique opportunity to either establish new perennial pastures for their cattle or utilize volunteer annual pasture and invest in more sheep breeders. In either case, large and irreversible investments fraught with multiple sources of uncertainty implies that one can gain useful insights by casting the investment problem in a real option context. The results suggest that required rates of return for each investment alternative are about 1% to 1.5% higher than standard NPV would suggest with sheep production having the lower required rate of return.     

Optimisation of a Large,Constrained Simulation Model using Compressed Annealing

Simulation models are valuable tools in the analysis of complex, highly constrained economic systems unsuitable for solution by mathematical programming. However, model size may hamper the efforts of practitioners to identify efficiently the most valuable management strategy. This paper investigates the efficacy of a new stochastic search procedure, compressed annealing, for the identification of profitable solutions in large, constrained systems. The algorithm is used to examine the value of incorporating a sown annual pasture, French serradella (Ornithopus sativus Brot. cv. Cadiz), between extended cropping sequences in the central wheatbelt of Western Australia. Compressed annealing is shown to be a reliable means of considering constraints in complex optimisation problems relative to the incorporation of fixed penalty factors in standard simulated annealing and genetic algorithms. French serradella is found to be an economic break pasture in the study region when weed populations are high or sheep production is lucrative.     

Piloting a systematic framework for public investment in regional natural resource management: Dryland salinity in Australia

The Salinity Investment Framework (SIF3) is designed to help environmental managers make better policy decisions about protecting key assets under threat of dryland salinity, a major degradation problem in Australia. This study reports results from applying SIF3 in partnership with two regional organizations (in the states of Victoria and Western Australia) with contrasting institutional powers and structures. We also engaged relevant policy makers with a view to influencing national policy. Available knowledge, science, and data were used to develop region-specific recommendations for public investment in salinity management. SIF3 proved easy to apply, requiring minimal changes from its original version. Establishing trust and credibility with stakeholders was extremely important. More time was required to be spent on communicating what SIF3 was and what it would mean for stakeholders than in applying it in the catchments. In both regions, recommendations included making a clear distinction between localized assets (such as a particular wetland) and dispersed assets (such as agricultural land as a whole); more targeted investment in spatially identified localized assets; using a broader range of policy tools; basing recommendations on the levels of public and private net benefits; anticipating the adoptability of sustainable land-management practices; and formally integrating relevant scientific, economic and social information with community values. The differences between current action and recommendations were significant in both regions, particularly in Victoria. As a result of our work both regions have decided to implementing a similar asset-based approach covering various environmental threats in addition to dryland salinity. The research indicates that it is feasible to use decision frameworks such as SIF3 to improve the rigour of decision making by community-based environmental management organizations. A broader range of policy tools are needed for dryland salinity, with less reliance on extension and small grants, and more emphasis on intervention around key assets and investment in technology development. We have influenced policy makers to some extent at state level and nationally through discussion of SIF3 in a national inquiry, preparation of a policy paper for peak multi-government policy committees, briefings and provision of advice on policy design. Despite this, achieving significant policy change at the state and national levels remains difficult for a number of reasons. Governments give limited signals to environmental managers to achieve environmental outcomes, being more concerned with community participation objectives and political considerations. We hope for significant policy change with increased scrutiny about sound decision making and public accountability.     

Managing complexity in modern farming*

Modern farming in Australia is no longer simple. Farms are large, multi‐enterprise businesses underpinned by expensive capital investments, changing production technologies, volatile markets and social challenges. The complexity of modern broadacre farming leads to the question: what is the nature of the relationship between farm business complexity and farm profitability? This study uses bioeconomic farm modelling and employs eight measures of complexity to examine the profitability and complexity of a wide range of broadacre farming systems in Australia. Rank order correlations between farm profitability and each measure of complexity show inconsistent relationships, although the most profitable farming systems are found to be reasonably complex on several criteria. Among the set of highly profitable systems are found some characterised by less complexity. A commonly acknowledged feature of farm business complexity is the annual workload of the farmer, yet the trade‐off between farm profit and this workload is found not to be large. A case is outlined where the farmer’s annual hours worked could be reduced by 9 per cent for a 3 per cent reduction in farm profit. If farmers’ workloads are proving problematic now, and in the future, then agricultural R&D, service delivery and policy development will need to focus more on being highly attractive to increasingly time‐poor farm managers.     

Testing the validity of responses to contingent valuation questioning

One way of assessing the validity of results generated through the application of the Contingent Valuation Method (CVM) is through the analysis of response sensitivity to factors expected to have an influence. Scope testing involves presenting at least two alternative impact scenarios to population sub-samples and testing for differences between the estimates generated. Most applications of the CVM in Australia have not involved scope testing and those that have yielded mixed results. These studies are reviewed. The results of scope sensitivity and other validity tests are presented for a study aimed at estimating the value of environmental damage caused by dryland salinity in the Upper South East of South Australia.     

The economic benefits of rabbit control in Australian temperate pastures by the introduction of rabbit haemorrhagic disease

The European rabbit is present in most Australian environments and causes economic loss in agricultural systems by reducing production and imposing control costs on producers and governments. Research into rabbit control has recognised the need for reliable benefit‐cost analysis to justify inputs into rabbit management. This paper provides estimates of the costs of rabbits in Australian temperate pasture systems and of the long‐term benefits of reducing rabbits by the introduction of rabbit haemorrhagic disease (RHD). Rabbits impose annual costs on wool producers in the temperate pasture areas of between 7.1 and 38.7 million Australian dollars (mA$) depending on their density. Controlling rabbits by RHD has the potential to generate substantial long‐term economic benefits by reducing grazing competition with sheep. Reducing rabbit costs by 25% generated 15‐year net present values (NPVs) between 18.4 and 97.3 mA$ at various pre‐RHD rabbit densities. A 50% reduction in rabbit costs increased the total NPVs between 36.9 and 202.4 mA$, virtually all of which was captured by temperate area wool producers. The corresponding benefit‐cost ratios were between 2.9:1 and 16.2:1 for a 25% rabbit reduction and 5.9:1 and32.4:l for a 50% reduction, where the total costs of the RHD program in the temperate pasture areas were incurred by the wool industry. The analysis provides guidelines for the economic evaluation of other pest problems in agricultural production systems.     

AN OPTIMAL CONTROL MODEL FOR INTEGRATED WEED MANAGEMENT UNDER HERBICIDE RESISTANCE*

The presence of weeds which have developed resistance to chemical herbicides is a problem of rapidly growing importance in Australian agriculture. We present an optimal control model of herbicide resistance development in ryegrass, the weed for which resistance is most commonly reported. The model is used to select the optimal combination of chemical and non-chemical control measures taking account of the trade off between short term profits and the long term level of herbicide resistance. Results indicate that given the threat of resistance there are benefits from integrating a combination of chemical and non-chemical control measures. The optimal strategy is found to include a declining herbicide dosage as resistance develops, with compensatory increases in the level of non-chemical control.     

The dynamics of phase farming in dryland salinity abatement

In Australia, soil salinisation has become a major concern. One way to deal with the problem is for farmers to plant trees or regenerate native bush. However, doing so raises several questions which involve optimal switching times, when switching involves a cost in the form of up-front investments. Optimality conditions are derived for the three-stage problem, and applied to dryland salinity control in Western Australia. Optimal management practices are found to be very sensitive to farmers' discount rates and to the speed at which the watertable rises or falls.     

Investigating improved pasture productivity change on the New South Wales tablelands

The productivity of improved pastures in Australia's southeastern grazing regions is now believed to be in a state of long-term decline. As yet, there is little economic evidence to support this perception. The analysis reported in this paper seeks to examine improved pasture Productivity change from an economic standpoint in a major Australian grazing area. The analysis rests on the central proposition that the Productivity of the livestock enterprises is a direct reflection of pasture productivity. Using both index number and econometric methods, the results indicate that while the annual growth in livestock and hence, improved pasture productivity has been positive over the period, there has been a significant decline in legume pasture productivity. Because these pastures comprise the bulk of improved pastures, the livestock Productivity of all improved pastures has declined in recent years. In contrast, the growth in livestock productivity from the perennial grass pastures continues to be high. The main reasons for legume pasture livestock productivity decline appear to be various important biological Problems and the long-term decline farmers' terms-of-trade.     

An economic analysis of sheep flock structures for mixed enterprise Australian farm businesses

A strategic question facing many mixed enterprise broadacre farm businesses in Australia is, ‘What sheep flock size and structure is most profitable to complement the farm’s cropping enterprises?' This study answers this question for a typical large mixed enterprise farm business in a key production region of Australia. Whole‐farm bioeconomic modelling, combined with broad‐ranging sensitivity analysis, is used to examine the profitability of different sheep flock structures and sizes. We find the most profitable flock structure is to run Merino ewes and turn off finished Merino or first‐cross lambs. The profitable selection of these flocks is robust to commodity price variation but does require the farmer to give more attention to sheep management. The correct choice of flock structure greatly adds to farm profit. A farm based on cropping and a self‐replacing Merino flock using surplus ewes for first‐cross, meat lamb production earns 33 per cent more profit than a similar farm that runs a traditional self‐replacing Merino flock that emphasises wool production. Of far less importance than flock structure, as a source of additional profit, is to increase flock size or adjust cropping intensity.