Zone Of Southern Australia Research Articles

Robbery in progress: Historical museum collections bring to light a mitochondrial capture within a bird species widespread across southern Australia, the Copperback Quail-thrush Cinclosoma clarum.

We surveyed mitochondrial, autosomal, and Z chromosome diversity within and between the Copperback Quail‐thrush Cinclosoma clarum and Chestnut Quail‐thrush C. castanotum, which together span the arid and semi‐arid zones of southern Australia, and primarily from specimens held in museum collections. We affirm the recent taxonomic separation of the two species and then focus on diversity within the more widespread of the two species, C. clarum. To guide further study of the system and what it offers to understanding the genomics of the differentiation and speciation processes, we develop and present a hypothesis to explain mitonuclear discordance that emerged in ourdata. Following a period of historical allopatry, secondary contact has resulted in an eastern mitochondrial genome replacing the western mitochondrial genome in western populations. This is predicted under a population‐level invasion in the opposite direction, that of the western population invading the range of the eastern one. Mitochondrial captures can be driven by neutral, demographic processes, or adaptive mechanisms, and we favor the hypothesized capture being driven by neutral means. We cannot fully reject the adaptive process but suggest how these alternatives may be further tested. We acknowledge an alternative hypothesis, which finds some support in phenotypic data published elsewhere, namely that outcomes of secondary contact have been more complex than our current genomic data suggest. Discriminating and reconciling these two alternative hypotheses, which may not be mutually exclusive, could be tested with closer sampling at levels of population, individual, and nucleotide than has so far been possible. This would be further aided by knowledge of the genetic basis to phenotypic variation described elsewhere.

Integrating crop modelling and production economics to investigate multiple nutrient deficiencies and yield gaps

A method is described for integrating crop modelling and production economics to quantify optimum applications of multiple nutrients and yield gaps. The method is demonstrated for crop production in the high‐rainfall zone of southern Australia. Data from a biophysical crop model were used to overcome the persistent problem of inadequate experimental data. The Mitscherlich function was expanded to accommodate four variable inputs – nitrogen, phosphorus, potassium and sulphur – and the expansion path was used to determine the economic optimum application of all four nutrients. Modelling revealed the state‐contingent yield potential and the extent to which unrealised yield could be explained by profit‐maximising behaviour and risk‐aversion by growers. If growers and their advisors were guided by the methods described, they would be better equipped to assess crop nutrient demands and limitations, predict yield potential, additional profit and the risks associated with high input systems in a variable climate. If scientists were more aware of the extra profits and the risks involved (as well as the quantitative relationships between inputs and outputs) when thinking about what to produce and how to do so, they would be more circumspect about the net benefits to be obtained from closing yield gaps.

Assessing the profitability of native pasture grazing systems: a stochastic whole-farm modelling approach

Grazing enterprises on the Central Tablelands of New South Wales employ a range of different strategies to manage temperate native grassland pastures common in the high rainfall zone of southern Australia. This paper uses a stochastic whole-farm simulation modelling approach to assess the impact of grazing system and stocking rate (SR) on the long-term profitability of a representative case-study enterprise. In particular, the impact of infrastructure costs, debt and downside risk, on whole-farm performance are examined over a 10-year planning horizon. In total, 12 different strategies were modelled under both price and climate risk, with a matrix of three paddock systems (1-paddock, 4-paddock and 20-paddock rotations) and four stocking rates (SR of 3, 4.2, 5.3 and 7 ewes/ha). Profitability was primarily driven by SR. In general, higher SR increased total farm output and annual profits under favourable conditions, although they were also associated with higher costs and greater downside risk in poor seasons, which in turn was magnified by the compounding effect of accumulating debt over time. When SR increased above 4.2 ewes/ha, it had a negative impact on lamb sale weights, resulting in lower prices due to lambs not meeting the ≥40-kg liveweight specification. Although this was offset by increased whole-farm production volumes at 5.3 ewes/ha, declines in profitability occurred at 7 ewes/ha as a result of significant increases in supplement feeding costs, and lambs not meeting sale weight specifications. The analytical scale of the analysis also had an impact on the relative profitability between alternative treatments. When assessed using a partial measure of economic analysis (gross margin per ha), there was little difference between paddock system treatments at the same SR. When the cost of additional fencing and water infrastructure were accounted for at the whole-farm analytical scale, the 20 paddock system was markedly less profitable than the 1- and 4-paddock rotations. This highlights the need for assessing production systems at an appropriate analytical and temporal scale to better understand the relationship between the key drivers of long-term profitability and risk. Overall there were relatively small differences in whole-farm performance between the four best performing strategies in this study. Given the trade-offs between profitability, downside risk, ground cover and feedbase sustainability, the lower risk 1- and 4-paddock systems with a SR of 4.2 ewes/ha are proposed as being optimal.

Seeding rate and cultivar effects on canola (Brassica napus) competition with volunteer wheat (Triticum aestivum)

Canola (Brassica napus L.) is an important rotational crop in the temperate cropping zone of southern Australia. Herbicide-resistant weeds are rapidly spreading and reducing canola grain yield and quality. Crop competition is a useful tool for reducing weed costs and dependence on herbicides, and retarding the spread of herbicide resistance. The potential interaction of canola seeding rate and cultivar for weed management has not been quantified in Australia. A field experiment was conducted in three environments to examine the impact of two contrasting canola cultivars (a low vigour type and a high vigour hybrid) at four seeding rates (10–100 plants/m2) on volunteer wheat (~50 plants/m2). Significant but variable effects of crop seeding rate, cultivar and weed were detected on canola density and grain yield, and on the suppression of volunteer wheat. The canola hybrids suppressed volunteer wheat more than the less vigorous cultivars in all the experiments. There was no benefit of increasing canola seeding rate above the normally recommended rate of 40 plants/m2 for weed suppression. The seed production of volunteer wheat on average doubled when canola density dropped from 40 to 10 plants/m2. Treatment effects on canola grain yield losses from weeds were less than those on weed suppression. The grain yield of both cultivars was reduced between 30% and 40% with weeds at a canola density of 40 plants/m2 and plateaued above this density in weedy conditions. Maintaining canola plant establishment and using competitive cultivars is critical to avoiding weed seedbank replenishment, and reducing canola yield losses from weed competition.

Preliminary assessment of bladder clover (Trifolium spumosum L.) as an annual legume for ley farming systems in southern Australia

Trifolium spumosum L. (bladder clover) is an aerial seeding annual legume that is adapted to fine-textured soils throughout the Mediterranean Basin. This article is the first of two papers that describe the process of domestication of T. spumosum as a new species to commercial agriculture. This paper describes a broad range of investigations into the ecology, agronomy and rhizobiology of this new species. Through a series of five experiments, we have tested the general hypothesis that T. spumosum accessions demonstrate a range of sought-after agronomic traits and offer an alternative to annual Medicago spp. for ley farming systems in the medium to low rainfall areas of the mixed crop/livestock zone of southern Australia. T. spumosum presents seeds at the top of the canopy in heads that do not readily shatter, so seed can be harvested using conventional cereal harvesters instead of the specialist suction equipment required for harvest of seed from annual T. subterraneum and Medicago spp. T. spumosum was found to be relatively fecund and had high levels of biomass production in comparison to the other annual legumes that were tested. The species also demonstrated high levels of within-season hardseededness (remaining hard in summer and softening in autumn) so seedbanks would be protected from summer rainfall events. In addition, T. spumosum showed high levels of between-season dormancy, which allows the species to carry a seedbank through a cropping phase or series of poor seasons. A herbicide experiment showed that clover species varied in tolerances, with T. spumosum the least sensitive of all of the legumes tested to Flumetsulam. A cross-inoculation experiment to measure symbiotic effectiveness revealed that WSM1325 (current clover strain) surpasses WSM409 (previous strain) in its relationship with the annual clovers of contemporary interest, while being highly effective at nitrogen fixation with T. spumosum. The results of this study and an associated investigation into feeding value indicate that T. spumosum offers a productive alternative to annual Medicago spp. on fine-textured soils. Of the T. spumosum accessions tested, the most promising has been released under the cultivar name of AGWEST Bartolo.

Development of an early season barrel medic (Medicago truncatula Gaertn.) with tolerance to sulfonylurea herbicide residues

Sulfonylurea (SU) herbicides are extensively applied to crops in the cereal-livestock zones of southern Australia. In low rainfall areas with alkaline soils, SU residues can persist over summer and can severely affect sown or regenerating medic pastures. A cohort of early season barrel medics (Medicago truncatula) bred and selected for tolerance to SU herbicide residues were evaluated at multiple field sites over 3 years (year of establishment and subsequent regeneration). Two lines (Z2438 and Z2415) were identified which had dry matter production and seed yield in the establishment year equivalent to their recurrent parent, Caliph, an early maturing, aphid-tolerant, barrel medic cultivar. They also had lower levels of hardseededness than Caliph, enabling them to regenerate in greater numbers in the following year and thus produce more dry matter. The two lines demonstrated good tolerance to simulated SU herbicide residues, producing up to 10 times the dry matter of the SU-intolerant parent Caliph. We anticipate that one or both of the two lines will be commercialised soon, enabling farmers in low rainfall areas with neutral-to-alkaline soils to successfully grow barrel medic pastures in the presence of SU herbicide soil residues resulting from applications to prior crops.

Barriers to implementation of natural resource management at the landholding level in the intensive agricultural zones of Southern Australia

The extent to which past natural resource management investment in Australia has actually improved the condition of natural resources is unclear. Many lessons remain to be drawn that can benefit NRM and help empower decision-makers responsible for resource stewardship. Twenty-three key decision-makers (policy-makers, landholders, scientists, land administration policy-makers) involved in NRM in Australia were interviewed using questions designed to identify the limitations in the existing approaches to NRM, and to identify where barriers to improvement exist. Lack of information to support decision-making, the small returns on agriculture in marginal areas, poor allocation of funding, reluctance to release information and a lack of whole-of-government approach to management were seen to be important barriers. We discuss the significance of these findings and conclude that a whole-of government approach to NRM and improved information would enhance decision-making.

Barriers to implementation of natural resource management at the landholding level in the intensive agricultural zones of Southern Australia

The extent to which past natural resource management investment in Australia has actually improved the condition of natural resources is unclear. Many lessons remain to be drawn that can benefit NRM and help empower decision-makers responsible for resource stewardship. Twenty-three key decision-makers (policy-makers, landholders, scientists, land administration policy-makers) involved in NRM in Australia were interviewed using questions designed to identify the limitations in the existing approaches to NRM, and to identify where barriers to improvement exist. Lack of information to support decision-making, the small returns on agriculture in marginal areas, poor allocation of funding, reluctance to release information and a lack of whole-of-government approach to management were seen to be important barriers. We discuss the significance of these findings and conclude that a whole-of government approach to NRM and improved information would enhance decision-making.

Evaluation of native and introduced grasses for low-input pastures in temperate Australia: experimental approach, site and genotype descriptions

This paper describes the experimental methodology, sites, seasonal conditions and germplasm used in the Australian Native and Low Input Grass Network (NLIGN). In 1998, eight sites were established across the temperate pastoral zone of southern Australia. These were located at Armidale, Binya, Sutton and Trangie in NSW; Springhurst in Victoria; Jericho in Tasmania; Flaxley in South Australie and Kendenup in Western Australia. A total of 62 lines were evaluated, of which, 29 were Australian native grasses and 33 were introduced. With differences in seed size among species and a lack of information on dormancy and germination characteristics of the native plants, seedlings were transplanted into the field on weed-mat as spaced plants. Lines were compared over a 3-year period from 1998 to 2001. Methods used for determination of forage production, persistence and palatability are described. Information detailing the original collection sites of the germplasm, a list of NLIGN sites where each genotype was evaluated, as well as a detailed description of sites and seasonal conditions is also presented.

Performance of native and introduced grasses for low-input pastures. 2. Herbage production

A total of 62 perennial grasses were evaluated for herbage production under low-fertiliser conditions at eight sites in the temperate zone of southern Australia from 1999 to 2001. A brief assessment of relative preference ranking by sheep was also made at the end of the experimental period. Four sites were in the high rainfall areas of south-east Australia, two in the drier mixed farming areas of western NSW, and two sites in Mediterranean southern Australia. Seven standard cultivars were included in the comparisons. Plants were grown from seed in glasshouses and transplanted to the field as spaced plants at 6–8 weeks age. Plants were harvested at irregular intervals by clipping to determine herbage production. Relative preference was determined by enclosing sheep in the experimental area at high stocking rates and estimating the amount of herbage grazed after 1, 3 and 5 days. Herbage production data were analysed using a multi-environment trial approach in which the environments comprised all combinations of sites and sampling times over the 3-year period. Overall, 73.6% of the total genetic variation for herbage production was accounted for. Average seasonal comparisons revealed good herbage production from Eragrostis curvula cv. Consol in both winter and summer, but in spring, several Dactylis glomerata lines were the most productive. Consol was not generally preferred by sheep, while D. glomerata lines were. Apart from cv. Consol, C4 species, including Bothriochloa macra, Chloris truncata, Enteropogon acicularis and Dichanthium sericeum had low herbage production in winter and spring, and had low acceptability to grazing sheep. These particular grasses were also not highly ranked for production in summer, although other C4 lines, notably selections of Themeda australis, Paspalidium jubiflorum and P. constrictum were. Few native C3 grasses had superior herbage production, although selections of Elymus scaber, Austrodanthonia fulva and A. duttoniana showed good growth rates. When considering further evaluation, grasses with very high recruitment (e.g. A. caespitosa) may need to be included, and the acceptability of grasses to sheep should also be assessed.

Performance of annual pasture legumes in cropping rotations in the cool temperate zone of south-eastern Australia

The relative performance of 3 alternative pasture legumes, in comparison with subterranean clover, grown in a 1:1 pasture:crop rotation was investigated during 1997–2001, at 2 sites in the high rainfall (>500 mm/year) zone of southern Australia. Seedling densities of the pasture legumes (before and after crop) were examined, along with herbage dry matter production, growth pattern and seed production. After 2 cycles of a 1:1 pasture:crop rotation, average seedling densities of balansa (Trifolium michelianum Savi var. michelianum), Persian (T. resupinatum L. var. resupinatum Gib. and Belli), arrowleaf (T. vesiculosum Savi.) and subterranean (T. subterraneum L.) clovers at the 2 sites were 6810, 2910, 680 and 630 plants/m2, respectively. Average cumulative herbage mass in 2001 was 7.49, 5.21, 8.53 and 7.76 t DM/ha.year, respectively. All clovers produced a large seed pool: balansa, 71.8 g/m2; subterranean, 38.9 g/m2; Persian, 35.5 g/m2; and arrowleaf, 35.4 g/m2. The results suggest that a 1:1 pasture:crop rotation is sustainable, in terms of pasture seed–seedling dynamics for each of the legumes, and that under this system the pasture legumes need to be sown only once.

The effects of grazing management on perennial ryegrass (Lolium perenne L.) herbage mass and persistence in south-eastern Australia

The effect of various grazing management treatments on newly sown and degraded perennial ryegrass pastures was studied at 6 different locations in the temperate high rainfall zone of southern Australia, as part of the Temperate Pasture Sustainability Key Program. The sites were located at Hamilton (2 sites, 1 grazed by cattle, 1 grazed by sheep) and Cavendish, western Victoria, Victor Harbor (Delamere), South Australia, and Ross and Parattah in Tasmania. Grazing management treatments significantly influenced the ryegrass mass and persistence of the pasture, but effects were not always consistent across sites. Autumn closure increased the perennial ryegrass content at Cavendish and Ross, as did the winter and summer closures at Ross. Spring closure increased the perennialryegrass content at Hamilton, Cavendish and Ross, but decreased it at Parattah, as did the summer closures at Parattah and Delamere. Fodder conservation decreased the ryegrass only at Parattah. At the Hamilton sheep site, and at Ross, mob stocking increased the ryegrass content, as did increased superphosphate treatments at Hamilton. Rotational grazing at Cavendish and Delamere increased the ryegrass content, as did the late spring or a late summer closure with a short autumn deferment at Cavendish and Ross, but both these treatments decreased ryegrass at Parattah. The treatments that had a negative effect at Parattah may have had a positive effect on cocksfoot at that site, creating competition for, and decreasing the ryegrass content. At most sites, treatments that included some spelling during spring to foster seed shedding, and spelling again in the following autumn to encourage germination seem to have been of benefit to the perennial ryegrass.

Low input grasses useful in limiting environments (LIGULE)

This paper presents a case for the selection and development of a wider range of perennial grasses for pastoral use in the higher rainfall (annual rainfall >500 mm) zone of southern Australia, especially the southern sector of the Murray–Darling Basin. There is also a need to reconsider the use of ‘high-input’ pastures on hill lands by developing more appropriate recommendations for managing existing native grass pastures productively. Past experiments which compared native grass based pastures with sown pastures promoted the view that indigenous grasses were inferior in most respects to exotic improved species. Even though many of the findings were confounded with fertiliser, stocking rate, and other treatment effects, they reinforced the general direction of cultivar development programs which in the temperate zone have been based mainly on the 4 exotic C3 species Phalaris aquatica L., Dactylis glomerata L., Lolium L. spp., and Festuca elatior var. arundinacea (Schreb.) Hackel (syn. Festuca arundinacea Schreb). This has led to an imbalance in the adaptability and range of species available to be sown in pastures, particularly for sowing on less productive landscapes where stony, shallow, infertile, acid soils limit the persistence of current cultivars. The pre-European vegetation of temperate Australia comprised species with a capacity for active growth and transpiration during summer. The water use pattern resulted in soil moisture being near capacity in late winter and spring, and exhausted by summer’s end. Replacement of this vegetation with annual-growing and summer-dormant C3 species has changed the water use pattern so that soils are drier in spring and wetter in autumn. This has reduced the pre-winter soil moisture deficit, which in turn has increased rates of deep drainage in winter. Land degradation in southern Australia is a consequence of this changed water use pattern. Deep drainage of water beyond the reach of plant roots has mobilised salts stored in the landscape and caused watertables to rise, which has led to large areas becoming saline. Lack of growth in summer in pastures consisting of senescent annual-growing species and dormant C3 perennial grasses limits utilisation of the products of nitrogen mineralisation, which allows nitrate nitrogen to accumulate in summer and be readily leached by rainfall in autumn. This increases rates of soil acidification. Although there may be scope to reduce deep drainage by increasing pasture growth in spring in areas where there is little likelihood of summer rainfall, this is not the case in south-eastern Australia where significant falls of rain occur during summer and autumn.

The long-term influence of superphosphate and stocking rate on the production of spring-lambing Merino sheep in the high rainfall zone of southern Australia

The productivity of spring-lambing fine wool Merino sheep grazing pastures sown in 1977 to perennial ryegrass and subterranean clover was assessed from 1989 to 1998. The pastures were fertilised each autumn with single superphosphate at 6 levels, and were stocked at a low, medium, or high stocking rate (SR) at each level of fertiliser. The average phosphorus (P) applied annually since sowing (P ) ranged from 1.6 to 32.9 kg/ha. The SRs used varied with fertiliser level in that they were higher where more fertiliser had been applied, so that the highest SR at each level of fertiliser ensured that the pastures were well utilised. Each ewe raised 1 lamb, which was removed at weaning. The influence of fertiliser on the productivity of the sheep at 4 classes (1–4) of SR (mean SR = 7.1, 10.1, 12.6, and 18.2 ewes/ha for classes 1–4, respectively) was described by: y = A−BCP, where y represents production per sheep (kg), and A, B, and C are constants. For greasy fleece weight, estimates of B and C were 1.59 and 0.84; and for SR classes 1–4, the estimates of A were 5.06, 4.89, 4.78, and 4.46, respectively. For weaning weight of lambs, estimates of B and C were 8.4 and 0.82, and estimates of A were 23.5, 22.7, 21.5, and 20.9 for SR classes 1–4. The mean fibre diameter (µm) of the wool was described by: D = 14.18+1.48 GW, where GW is the mean greasy wool produced annually per sheep (kg) averaged over all sheep and years for each of the 18 treatments. The price (cents/kg) of wool with a fibre diameter D (P D) was given by: P D = 12197+4.94P2 + 688D−0.1945P20D − 5810√D, where 20 µm wool is P20 cents/kg. Supplements were fed if the body condition of ewes fell to a predetermined level. The supplement fed per ewe each year (S), expressed as metabolisable energy (in MJ) was described by: S = −602 − 44.1S R + 178.5P + 8.71S R P +539 √SR− 338.5√P−70.8P√SR, where S R and P represent the mean stocking rate (ewes/ha) and mean P applied annually. When a current set of costs and prices was applied to these equations, the maximum gross margin for a SR of 7.1 ewes/ha was $AU119/ha with 8.6 kg P/ha applied annually, and $AU262/ha for SR of 18.2 ewes/ha with 17.6 kg P/ha applied annually. If income derived from sheep is maintained constant, intensifying the sheep enterprise from the low to the high SR system would involve increasing sheep numbers by about 17%, but would release about 55% of the farm’s area for another purpose.

The distribution and pedology of soil mosaics, Barossa District, South Australia

Black earths and Australian brown earths occur in ways contrary to normal expectation in the red brown earth zone of southern Australia. The soil pattern is an intimate fine-grained mosaic of the three great soil groups changing within a few yards from one to another in an erosional landscape and quite out of accord with the underlying Precambrian metamorphic rocks. Field studies reported here ascribe the black earths to thin intermittent remnants of a lacustrine Tertiary clay as parent material, and the brown earths to a mixture of the clay with the normal weathering products of the underlying rocks. A substantial part of the evidence for this is derived from their distribution as a horizontal lamina tracing out a contour band in the mid and upper mid slope topography. There is a nice accordance between the elevations of this band and of an adjacent, elevated, dissected black clay plain. The three soils are everywhere found in places which are consistent with the postulate that their parent materials were put there by processes of erosion, dissection, and redistribution of distinctly separate hill and high plain landscapes.