Wheatbelt Of Western Australia Research Articles

Breeding by Barn Owls Tyto alba in artificial nest hollows established for an endangered black cockatoo in the northern wheatbelt of Western Australia

ABSTRACT Barn Owls Tyto alba were recorded breeding in natural nest hollows in a Wandoo Eucalyptus wandoo woodland in the northern wheatbelt of Western Australia infrequently and at low densities during the period 1969-2022. During a record cropping season in 2022, Barn Owls were first recorded nesting successfully in natural hollows and in artificial nest hollows designed for use by Carnaby’s Cockatoos. The large clutch sizes (5-7) and complete fledging success observed in three artificial nest hollows was likely facilitated by a large House Mouse Mus musculus population associated with the record cropping season experienced at the study site.

The breeding biology of the Western Red-tailed Cockatoo Calyptorhynchus escondidus in the wheatbelt of Western Australia

ABSTRACT A breeding population of Western Red-tailed Cockatoos Calyptorhynchus escondidus was studied between July 1974 and December 1981 at Nereeno Hill, in the northern wheatbelt of Western Australia. Egg-laying occurred during two clearly defined periods each year; with peaks mid-March to mid-April (Autumn breeding) and early-August to mid-October (Spring breeding). Thirty-two percent of the 459 eggs laid during the study were laid in Autumn and 68% in Spring. Growth rates of nestling wings and body mass were similar between seasons and years. Nearly one third of breeding attempts failed during incubation and 40.7% successfully fledged a nestling. Fledgling survival in the first year was low (17.5%), however, annual survival was higher after the first year; 80.0% after four years. Birds were killed by Wedge-tailed Eagles Aquila audax, shot by farmers, and drowned in stock troughs. Based on evidence from one individually-marked pair, Western Red-tailed Cockatoos may form long lasting pair bonds. While females breed every 12 months, some have bred in both Autumn and Spring seasons. Young Red-tailed Cockatoos remain with their parents up to two years after fledging, and adults may have young from two breeding seasons accompanying them. The breeding biology of Red-tailed Cockatoos is compared with that of closely related species from the genera Calyptorhynchus and Zanda. Threats to the species are loss of mature hollow-bearing trees and almost complete dependence on the seeds of Double Gee Emex australis, an introduced agricultural weed, for food.

Identifying areas of high drought risk in southwest Western Australia

Drought is a significant natural hazard in Australia, associated with financial hardship and damage to soils and vegetation. With droughts expected to become more frequent and more severe as climate change progresses, it is increasingly important to identify drought risk and assess community-level drought resilience at the appropriate spatial, temporal and administrative scale for decision-making. Here, we have used spatial multi-criteria analysis (MCA) to identify regional priority areas for the implementation of drought resilience interventions or investment in southwest Western Australia (WA). The MCA method involves the systematic integration of spatial data of different magnitudes and units through standardisation and weighting, and the visualisation of aggregated data to a single parameter output map. The study region is home to the WA grains industry, the largest agricultural contributor to the economy and one of the regions most impacted by climate change in Australia to date, experiencing consistent reduction in rainfall and recurrent drought over the last several decades. We modelled drought exposure, sensitivity and adaptive capacity for the region, incorporating spatially explicit climate, environmental, social and economic data, and produced a suite of priority areas maps that were sense-checked against a participatory mapping process. The maps highlight the northern and eastern Wheatbelt of WA as areas at high risk from drought and have the potential to serve as a powerful tool for local-level drought resilience decision-making. Most of the data we used are publicly available, and the vulnerability framework applied allows for wide replication within and beyond southwest WA.

Clutch size, incubation and nestling periods, and age estimation of nestling Red-tailed Black Cockatoos Calyptorhynchus banksii escondidus in the Western Australian wheatbelt

ABSTRACT The breeding ecology of the Red-tailed Black Cockatoo Calyptorhynchus banksii escondidus was studied in the northern wheatbelt of Western Australia from the austral spring of 1974 to the end of 1981. The usual clutch was one egg, but 8 of 465 clutches were of two eggs, none of which produced two fledglings. The incubation period was 29 days, similar to that of other species of black cockatoo with similar body mass. The nestling period was 80-84 days, nearly 17% longer than the similarly-sized Carnaby's Cockatoo C. latirostris. The ages of nestling Red-tailed Black Cockatoos may be estimated by comparison with photographs taken of nestlings of known age or estimated more precisely from the length of the nestling's folded wing. Aging nestlings enables the calculation of laying and hatching dates.

Uneven crop residue distribution influences soil chemical composition and crop yield under long-term no-tillage

Conservation agriculture has three main components: crop residue retention; minimal soil disturbance; and diverse rotations. Whilst retaining crop residues on the soil surface is important to prevent erosion and conserve water, high residue amounts can also have negative effects. Residue spread behind harvesters is not always uniform, therefore, it is important to understand the impact of uneven residue spread on crop performance. These problems are likely to increase as more farmers windrow and burn residues for weed control, harvesters become larger and controlled traffic systems are implemented. The effect of residue distribution on soil properties and crop establishment and yield was studied under no-tillage and controlled traffic in cereal (wheat-wheat-barley) and diverse (wheat-legume-canola) rotations, over the final six years of a larger 12-year (2007–2018) rotation trial, in the Wheatbelt of Western Australia. Within each crop and rotation, residue management consisted of either spreading or windrow-burning and measurements were taken from three locations relative to the harvester wheel tracks: centre (between harvester wheel tracks), mid (2.25 m perpendicular) and outer (4.5 m perpendicular), representing the ~9 m working width of the machinery. In most years, the distribution of crop residue behind the harvester was uneven, with up to twice as much residue directly behind the harvester compared with mid and outer locations. Differences in residue amount had positive, negative or no effect on crop establishment and yield, depending on the crop and residue type and climatic conditions. Increasing residue amount had a positive effect on establishment and yield when conditions were dry around seeding and early crop growth stages, possibly associated with increased water availability with increased residue load. Conversely, there were negative effects when frost occurred at anthesis or under high rainfall conditions, the latter due to physical impairment, increased disease or lack of available nitrogen. Negative effects only occurred with cereal residue and could be minimised by growing more break crops, even under high residue loads. In the longer term, higher residue amounts resulted in increased soil nutrients behind the harvester, which increased yields in some years. Therefore, research to improve uniformity of residue spread behind harvesters is crucial. Otherwise, variation in crop performance will increase as harvesters get bigger and, in the long term, periodicities in soil chemistry under controlled traffic systems will occur.

Effects of dryland summer cover crops and a weedy fallow on soil water, disease levels, wheat growth and grain yield in a Mediterranean-type environment

Numerous studies have reported wide-ranging benefits of cultivating cover crops during the typical fallow period in temperate cropping systems. However, data on the impacts of summer cover crops in water-limited, Mediterranean-type climates, is lacking. A 3-year field experiment was conducted near the town of Northam in the wheat-belt of Western Australia to test the hypothesis that inclusion of summer cover crops would increase ground cover, water storage and grain yield in subsequent wheat crops. White French millet ( Panicum miliaceum ) and cowpea ( Vigna unguiculata ) cover crops and a weedy fallow were compared to a typical chemical fallow over the summer period. Autumn groundcover was 10–30% higher when summer weeds were left uncontrolled compared to the chemical fallow treatment. Dry-sown and late established (February) millet failed to increase groundcover, whereas cowpea demonstrated a small increase (~9–10%) in one season, when cowpea biomass approached 1 t ha −1 . Cover crops and weeds growing over summer had no significant effect on total plant available water (0–50 cm depth) prior to sowing wheat in any season. However, there was less readily available soil N in the cover crop (less 10–30 kg N ha −1 ) and weedy fallow (less 50 kg N ha −1 ) treatments prior to the second wheat crop. Despite some significant effects of weedy fallow and cowpeas on Gaeumannomyces graminis var tritici (take-all) and Didymella pinodes (causing black pea spot), disease levels were low and thought to pose little risk to following winter crops. Wheat grain yields were not significantly different between treatments, other than a low yield after cowpeas in 2015 due to a low wheat emergence count. Grain protein and screenings were not generally affected by summer fallow treatment in any year, except for higher screenings after the weedy fallow in one year. Given the limited impacts of cover crops and weeds on soil water and disease, it is possible that summer cover crops may be able to be integrated with cereal winter rotations in Western Australia without yield reductions in wheat crops. In light of current chemical usage, issues around herbicide residues in soil and herbicide-resistant weeds, it would be worthwhile revisiting the need for chemical fallow, particularly in the higher rainfall areas.

Irruptive dynamics of the brush-tailed bettong (

Context The fluctuating fortunes of the brush-tailed bettong have seen this species classified as ‘Rare or Likely to Become Extinct’ in the 1970s, delisted and hailed as a conservation success in the 1990s, and re-listed as ‘Critically Endangered’ in 2008. Key actions to recover this species, broad-scale fox control and reintroduction to fox-free habitat, have had variable success. Aims To monitor the reintroduction of bettong to fox-free habitat of Wadderin Sanctuary in the eastern wheatbelt of Western Australia. Methods Growth of the population was monitored over a 12-year period by regular trapping throughout the sanctuary. Key results The population increased monotonically to peak at 305 individuals (0.71 ha−1) at 7.5 years following release, before subsequent decline. Population growth was accompanied by a significant decline in mean condition and a reduction in the proportion of females with pouch young or lactating, presumably owing to resources per head gradually declining. The proportion of large pouch young relative to total young carried by females declined as woylie numbers increased, suggesting that, increasingly, pouch young did not go to full term. Declines in population number, condition and reproduction were exacerbated by dry seasons. Bettongs established successfully, despite a succession of single feral cats within the 427-ha sanctuary. The removal of the last cat, 8 years following the establishment of bettongs, had no obvious impact on bettong numbers, as, at this point, their population was stabilising because of declining body condition and reduced reproductive output. Conclusions The observed pattern of population growth of bettongs was consistent with an herbivore irruption consequent of a release of a species to new habitat. Decline following peak numbers appeared as a result of density-dependent resource limitation (declining resources per head with increased abundance) interacting with years of low rainfall. Implications The dynamics of irruption and decline of herbivores are relevant to management of reintroduced populations to fenced predator-free sites and, potentially, to unfenced populations following release from predation.

Crop rotation can be used to manipulate residue levels under no-tillage in a rainfed Mediterranean-type environment

Fields with low residue levels (<∼2 t ha−1) are prone to erosion and reduced water conservation in semi-arid environments, and high residue amounts (>∼4 t ha−1) can reduce crop establishment and herbicide efficacy. Furthermore, increasing herbicide resistance in southern Australia has resulted in an increase in non-herbicide control measures like ‘windrow burning’, which reduces residue levels. Therefore, it is important to understand crop residue dynamics in this Mediterranean-type environment and any management factors that can be used to regulate amounts of residue. This paper reports on the residue dynamics in a 12-year experiment (2007–2018) in the Wheatbelt of Western Australia, comparing rotations that included: cereal (cereal/cereal/cereal); diverse (wheat/legume/canola); farmer (wheat/barley/break – legume or fallow); and wheat monoculture. Crop residue was either spread behind the harvester (retain) or windrowed at harvest and burnt before seeding (windrow burn). Residue quantity was measured shortly after harvest (usually in December), prior to seeding (usually April), and around anthesis (September).Crop residue amounts were highest after harvest each year and then declined over the next 12 months, until the next harvest. Residue quantity was greatest following years of high rainfall and good crop growth. Within rotations, residue quantity was highest with retained residue in the cereal rotation and wheat monoculture, averaging 5.0 t ha−1 prior to seeding, which could present management problems at seeding time in some years. Residue amounts were lower in the diverse rotation, and levels declined after wheat (4.5 t ha−1) through to legume and canola residue at 3.8 t ha−1. Lowest residue occurred with windrow burning in the farmer rotation, which included one fallow every three years from 2013, with quantities averaging ∼1 t ha−1. Overall, windrow burning before seeding reduced residue amount by ∼50 % compared with retaining the residue.Retaining all residue in a cereal-dominant rotation produced highest residue quantities in this Mediterranean-type environment, but may lead to problems with crop establishment. Residue quantity was reduced to optimal levels by including legume crops or canola in the rotation, as these residues were more rapidly broken down than cereal residues, whilst maintaining residue retention practices.

Effectiveness of dogs for detecting feral cat scats in wheatbelt reserves of Western Australia

Abstract Context Dogs are increasingly being used in conservation work to collect information on species abundance, distribution, occupancy and other biological measures. Monitoring feral cats through the use of detection dogs could provide a useful technique to complement existing feral cat survey and control methods. Aim To demonstrate and quantify the ability of trained detection dogs to reliably and efficiently detect feral cat scats when present in woodland conservation reserves in the Wheatbelt of Western Australia. Methods Cat scats were randomly placed into 466 1.5 ha (150 m × 100 m) quadrats in Tutanning Nature Reserve, Western Australia, and the location of the scat was recorded. Quadrats were then independently searched by dogs walking a central transect line and the locations of all scats detected were recorded, with the distance from the scat to the transect subsequently being calculated. Data collected allowed the relationship between distance from the transect and detection probability to be used to assist modelling of detection probabilities. Key results Dogs detected scats in 213 (55%) of 384 quadrats that were searched using a single transect line method. All indications of a find by the detector dogs were associated with a cat scat (no false indications). Detection probabilities for scats declined with distance from the transect line and with an increasing age of the scat. Simulations to investigate management options for cat control programs quantified effort required to detect cat scats under varying densities. Conclusion Dogs were highly efficient at detecting scats within the woodland environment of the Western Australian wheatbelt. The effort required to detect a scat was considerably higher when cat density was low. Implications On the basis of the detection probabilities derived from the present study, trained scat-detection dogs can be expected to efficiently search woodlands and find cat scats by using an effective sweep width of 100 m (50 m either side of a transect) when scats are fresh. Sweep widths need to be reduced significantly if it is important to locate scats that have been exposed to the elements for greater periods of time, or to search habitats where terrain and vegetation cover are more challenging.

Planting configuration affects productivity, tree form and survival of mallee eucalypt in farm forestry plantings

Mallee eucalypts have been extensively planted in the Western Australia wheatbelt for salinity mitigation and as a short-rotation coppice crop for the production of cineole and bioenergy feedstocks. Mallee has been planted in wide-spaced narrow belts (2–6 rows) within annual crops and pasture, but optimal planting configurations have not been determined. Here, we assess the biomass yield responses of Eucalyptus loxophleba ssp. lissophloia and E. polybractea to; four row treatments (1, 2, 4 and 6 row belts) and five within-row spacing treatments (1, 1.5, 2, 3 and 4 m). Thirteen years after planting, the row effects on plot-level biomass productivity of E. loxophleba ranged from 4.3 to 21.2 Mg ha−1 year−1. For E. polybractea, both row number and within-row spacing affected yield, which ranged from 2.7 to 18.8 Mg ha−1 year−1. For both species, the highest growth rates were observed in the one-row belts with shorter (< 3 m) within-row spacing. Within the belts, reductions of growth rate were observed with additional rows, due to increased competition and significant suppression of internal rows; and with wider within-row spacing, due to lower initial planting density. However, when including the area between belts, wider belts generated more biomass. For both species, average tree size decreased with additional rows and shorter within-row spacing. For both species, the number of stems per tree increased with wider within-row spacing, and also for E. polybractea, with fewer rows. The substantial variation in productivity, tree size and form found in these results will affect harvestability and ultimately the economic viability of future mallee plantings.

Limits in complexity: the contextual boundaries of Peter Carstairs’ "September"

Peter Carstairs’ 2007 film September is a quiet, intimate contemplation of friendship, coming of age, and ‘the subtle side of racism’ in 1968 Australia (Carstairs in Robertson 2007, p. 16). In the Wheatbelt of Western Australia, Ed Anderson (Xavier Samuel) the son of a wool and wheat farmer, and Paddy Parker (Clearance John Ryan) the son of an Aboriginal labourer on the Andersons’ property, navigate the strains placed on their relationship by complex long-standing prejudices and the changing nature of the Australian political world.

Has historic climate change affected the spatial distribution of water-limited wheat yield across Western Australia?

Climate change has likely impacted crop yield potential in major rain-fed crop-growing regions. However, the impact on the spatial pattern across regions is unclear. Here, the wheat belt of Western Australia was used as a case study to investigate the effect of historical climate change on the spatial patterns of water-limited crop yield. We used 117 years (1900–2016) of observed daily climate data on ~ 5 km × ~ 5 km grids to map and quantify the spatial-temporal changes in water-limited wheat yield simulated by the APSIM model. The climate data were split into four periods based on distinct changes in rainfall (Period 1, 1900–1934; Period 2, 1935–1974; Period 3, 1975–1999; and Period 4, 2000–2016). The results showed that the observed decreases in rainfall shifted the regional wheat yield potential towards the southwest of the wheat belt by an average of 70 km between the first and last periods. Observed increases in CO2 counteracted this by about half of this movement. Actual wheat yields achieved by farmers have not decreased, thanks to improvements in crop genetics and management, but the simulated decrease in water-limited yields has meant that actual yields in this region are not as high as they might have been. Future climate change is likely to continue to impact on water-limited crop yield and its spatial pattern in Western Australia. Cropping systems will need to continually evolve to cope with a changing climate, and every aspect of agronomy and genetics needs to be considered. Without continuing improvements, there will likely be a decrease in wheat yield across this cropping region.

Co-infection of wheat by Pyrenophora tritici-repentis and Parastagonospora nodorum in the wheatbelt of Western Australia

The pathogenic fungal species Pyrenophora tritici-repentis (Ptr) and Parastagonospora nodorum (Pan) are common in many wheat-producing parts of the world. These two fungi cause tan spot and septoria nodorum blotch, respectively, frequently co-infecting wheat leaves. Empirical studies of this and other co-infections are rare because of the visual similarity of symptoms and the lack of robust methods for quantifying the abundance of pathogens associated with the co-infection. Here, we use a recently developed molecular method that simultaneously distinguishes and quantifies, in DNA equivalent, the abundance of Ptr and Pan, thereby allowing the prevalence of co-infection to be determined. The study examines the prevalence of co-infection under field conditions, at three widely spaced sites and on three wheat (Triticum aestivum L.) cultivars varying in disease resistance. Co-infection by Ptr and Pan was almost ubiquitous (overall prevalence 94%), and Pan DNA was detected only in association with Ptr. Although Ptr and Pan commonly co-infected, Ptr was more abundant during early and mid-season, at 80% of total fungal abundance when crops were tillering and 67% at booting stage. Pan became as abundant as Ptr when crops reached flowering. Variability in total fungal abundance and disease severity was primarily determined by cultivar; however, Ptr was the more abundant despite differences in cultivar resistance to this pathogen.

Spatial patterns of estimated optimal flowering period of wheat across the southwest of Western Australia

In order to maximize wheat yield, farmers need to match sowing date and cultivar phenology to ensure that flowering occurs within the optimal flowering period, which minimizes the combined impacts of frost, heat and water stress on grain yield. The optimal flowering period is location specific and so far the spatial patterns of optimal flowering period have not been defined. This study conducted a simulation analysis using multiple sowing dates, long-term (1967–2007) and fine-scale gridded (0.05° × 0.05°) climate data. The simulations were used to identify the spatial patterns of the optimal flowering periods (defined as ≥ 95 % of the maximum mean yield occurred during sensitive growth periods) across the southwest of Western Australia. The results showed that optimal flowering periods of wheat were mainly determined by the spatial pattern of climate, with the cultivar and soil type playing only a minor role. There were clear geographical patterns of the optimal flowering periods across the wheatbelt of Western Australia, with opening and closing dates of the optimal flowering periods being earlier (23 Jul–30 Sep) in the northeast and later (23 Aug–21 Oct) in the southwest. There was a relatively small difference in the duration of the optimal flowering period across most areas of the wheatbelt. Provided flowering occurs within the optimal flowering period, a slow-developing cultivar sown early would achieve higher yield, due to longer period to accumulate biomass, than a fast-developing cultivar sown late. These results provide Western Australian growers with knowledge of how to match sowing date and cultivar to achieve flowering within the optimal flowering period.

Soil acidity, lime application, nitrogen fertility, and greenhouse gas emissions: Optimizing their joint economic management

Soil acidity is a major limiting factor for crop production in many farming systems worldwide. Lime application is the most common practice to mitigate soil acidity. There are complex economic interactions between application of lime and nitrogen fertilizer, with the greenhouse gas emissions associated with the use of these inputs adding further complexity. We employ a non-linear dynamic optimization model to determine economically optimal application strategies for lime and nitrogen fertilizer accounting for the social cost of the resulting emissions of greenhouse gases. The model is applied in three zones with different rainfall levels, in the northern wheatbelt of Western Australia. Rainfall has important influences on results through its effect on the dissolution and leaching of lime, leaching of nitrogen, and the yield potential of crops. Results show that nitrogen-related decisions, such as the type of nitrogen fertilizer and crop rotation, have a substantial impact on optimal lime application rates and resulting emissions. For example, the use of ammonium sulfate, rather than urea, reduces emissions. Similarly, by allowing a reduction in nitrogen fertilizer use the incorporation of legume crops like lupin can reduce emissions by 50%, relative to a wholly non-legume crop rotation. Although carbon pricing reduces emissions, the magnitude of the reductions is modest in all modeled scenarios. The private cost to farmers of a carbon tax in this case study region is small, although the net social benefit of the carbon tax in this case study is smaller still, even without accounting for the transaction costs of operating the tax system.

Comparative analysis of genetic structures and aggressiveness of Fusarium pseudograminearum populations from two surveys undertaken in 2008 and 2015 at two sites in the wheat belt of Western Australia

Fusarium crown rot (FCR), caused predominantly by Fusarium pseudograminearum (Fp) in Australia, is an important fungal disease of wheat and barley. FCR causes significant yield losses and reduced grain quality worldwide. This study investigated the population dynamics of FCR‐causing F. pseudograminearum isolates from Western Australia (WA), a major wheat‐growing region. Wheat samples were collected from a total of seven different sites in 2008 and 2015. Two sites, Tammin and Karlgarin, with moderate to high FCR incidence, were intensively sampled in both years. The results revealed significant increase in Fp isolation frequency between 2008 and 2015. Over 86% of 1100 Fusarium isolates were Fp in 2015 compared with 59% of 639 isolates from 2008. Mating type idiomorphs, toxin chemotypes and population genetic structures were determined for a subset of 279 Fp isolates (132 isolates from 2008 and 165 from 2015). Mating type analysis revealed differences in MAT1‐1 and MAT1‐2 distributions between Tammin and Karlgarin for both years. Results also showed that 97.6% of Fp isolates analysed had the 3‐ADON trichothecene chemotype. Additionally, for the first time in Australia, the 15‐ADON chemotype was identified in 2.3% and 2.4% of Fp isolates from 2008 and 2015, respectively. The genetic structure of Fp population determined using 21 cleaved amplified polymorphic sequence (CAPS) markers revealed a high level of genetic variation within and between populations. In addition, 2015 isolates from Tammin and Karlgarin were significantly more aggressive (P &lt; 0.0001) than 2008 isolates. This finding may have implications in managing this significant fungal disease.

Breeding site fidelity, and breeding pair infidelity in the endangered Carnaby’s Cockatoo Calyptorhynchus latirostris

The ecology and behaviour of the endangered Carnaby’s CockatooCalyptorhynchuslatirostrishave been studied in detail at Coomallo Creek in the northern wheatbelt of Western Australia from 1969 until the present. Results of research on this breeding population conducted on individually marked birds from 1970 to 1990 were compared with results from analyses of DNA taken from nestlings in the study area from 2003, 2005, and each year from 2009 to 2013. Analyses of DNA confirmed earlier findings about the stability of adult breeding pairs, and that females used the same breeding hollow they used previously, provided the hollow was not occupied when they returned to breed. When moving to another hollow, they chose a hollow in the same vicinity of the previous hollow. Analyses in 22 cases where DNA was obtained from both nestlings of a breeding attempt revealed that in six (27.3%) cases, the second egg was fertilised by a male not paired with the female. These extra-pair copulations were not suspected during the earlier study based on observations of individually marked birds.

Transformative and systemic climate change adaptations in mixed crop-livestock farming systems

Mixed crop-livestock farming systems provide food for more than half of the world's population. These agricultural systems are predicted to be vulnerable to climate change and therefore require transformative adaptations. In collaboration with farmers in the wheatbelt of Western Australia (WA), a range of systemic and transformative adaptation options, e.g. land use change, were designed for the modelled climate change projected to occur in 2030 (0.4–1.4° increase in mean temperature). The effectiveness of the adaptation options was evaluated using coupled crop and livestock biophysical models within an economic and environmental framework at both the enterprise and farm scales. The relative changes in economic return and environmental variables in 2030 are presented in comparison with a baseline period (1970–2010). The analysis was performed on representative farm systems across a rainfall transect. Under the impact of projected climate change, the economic returns of the current farms without adaptation declined by between 2 and 47%, with a few exceptions where profit increased by up to 4%. When the adaptations were applied for 2030, profit increased at the high rainfall site in the range between 78 and 81% through a 25% increase in the size of livestock enterprise and adjustment in sowing dates, but such profit increases were associated with 6–10% increase in greenhouse gas (GHG) emissions. At the medium rainfall site, a 100% increase in stocking rate resulted in 5% growth in profit but with a 61–71% increase in GHG emissions and the increased likelihood of soil degradation. At the relatively low rainfall site, a 75% increase in livestock when associated with changes in crop management resulted in greater profitability and a smaller risk of soil erosion. This research identified that a shift toward a greater livestock enterprises (stocking rate and pasture area) could be a profitable and low-risk approach and may have most relevance in years with extremely low rainfall. If transformative adaptations are adopted then there will be an increased requirement for an emissions control policy due to livestock GHG emissions, while there would be also need for soil conservation strategies to be implemented during dry periods. The adoption rate analysis with producers suggests there would be a greater adoption rate for less intensified adaptations even if they are transformative. Overall the current systems would be more resilient with the adaptations, but there may be challenges in terms of environmental sustainability and in particular with soil conservation.

A case study: what is leached from mallee biochars as a function of pH?

Biochar is widely considered as a soil amendment. This study aims to investigate the leaching of macronutrients (K, Mg and Ca) and organics from biochars produced from mallee biomass (wood, leaf, bark) in a fluidised-bed pyrolyser at 500 °C. Biochars were soaked in solutions of varying pH values and shaken for a pre-set period of time ranging from 1 h to 4 weeks. The initial pH values of the leaching solutions used (3.4, 5.5, 7 and 8.5) covered the pH range of the soils in the Wheatbelt region of Western Australia (WA). For these bark, leaf and wood biochars, we can conclude that the biochars have a liming capacity for the acid soils of the WA Wheatbelt, depending on the feedstock. The maximum leachabilities and leaching kinetics of the macronutrients K, Mg and Ca depend on the pH of the solution in which biochar was soaked. Apparently, Ca, K and Mg in biomass are converted into different species upon pyrolysis, and the biomass species are critical for the extent of the leachability of macronutrients. Further, the chemical form of each nutrient retained in the biochars will dictate the kinetics as a function of soil pH. This study’s GC/MS analysis of solvent extraction of the biochars showed potential toxicity due to the leaching of light organic compounds when biochars are added to soils. Furthermore, this study also showed the influence of pH on the leaching of large aromatic organics from the biochars. Apart from the pH of leaching solution, the influence of the biomass feedstock on the leaching kinetics of large aromatic organics from biochars was demonstrated. These leached aromatic organics were characterised by UV-fluorescence spectroscopy.

Changing water system vulnerability in Western Australia's Wheatbelt region

Within a changing world where freshwater resources are coming under increasing pressure, assessing water system vulnerability is critical for enabling adequate water resource management. Quantitative assessments of socio-economic and environmental factors which contribute to water system vulnerability can provide a strong evidence base on which to base decision-making. A range of drivers including population growth, agricultural intensification and industrial activity are placing greater demand on freshwater supplies in Western Australia. In combination with changing climatic conditions resulting in a warmer and drier environment in southwest Western Australia, these pressures have diminished the quantity of available freshwater supplies for agricultural districts. In this paper we provide a quantitative assessment of water supply and demand vulnerabilities for the Wheatbelt region of the state of Western Australia (WA). This region provides significant agricultural and mineral resource contributions to the state economy. The potable water supply for human consumption in this region is almost entirely drawn from a different geographic area, and conveyed by means of an extensive pipeline network to the Wheatbelt region. Competition for freshwater resources is high with increasing population pressures from expansion of the state's capital city, Perth, encroaching north- and eastwards into the Wheatbelt. To assess water vulnerability we conceptualise the water system components and select a series of socio-economic and environmental indicators which best represent the inherent vulnerabilities associated with water supply and demand in the Wheatbelt. Water supply, demand and overall system vulnerabilities were spatially assessed for the years 2001, 2006 and 2011. Results indicate that biophysical indicators of supply capacity have the greatest influence on overall vulnerability for each time period, however the spatial variability of specific vulnerability factors is much more nuanced. Our assessment of water vulnerability will enable water resources managers and policy-makers within the Wheatbelt and at the state level to better assess water supply and demand pressures. However, our robust methodology also allows for transferability to other locations experiencing water stress as a comprehensive approach for examining historic and future impacts of water resource availability on socio-ecological systems.