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Purposes: Soil labile carbon (C) and nitrogen (N) pools are vital indicators of soil fertility and soil organic matter (SOM) dynamics. We aimed to evaluate the short-term effects of biochar application on soil labile C and N pools in nutrient-deficient soil in subtropical Australia. Materials and methods: A 9-month field study was conducted to investigate the short-term changes in soil water-extractable organic C (WEOC) and total N (WETN) as well as hot water-extractable organic C (HWEOC) and hot water-extractable total N (HWETN) in response to biochar application rates under two Acacia species (Acacia leiocalyx (A. leiocalyx) and Acacia disparrimma (A. disparrima)) and Eucalyptus psammitica (E. psammitica) in a native subtropical forest in southeast Queensland, Australia. Biochar was applied at three rates: 0 t ha−1 (B0), 5 t ha−1 (B5), and 10 t ha−1 (B10). We collected soil samples from 0–5 cm, 5–10 cm, and 10–20 cm depth after 6 months of biochar application, and soil samples at 0–5 cm depth were also collected shortly before biochar application and after 1, 2, 3, 6, and 9 months of biochar application. Results: Soil WEOC and WETN significantly decreased with the biochar application rate during the study period. In the 10–20 cm layer, soil WEOC, WETN, HWEOC, and HWETN under E. psammitica were significantly higher than those under the Acacia species. Sampling time also significantly affected the soil labile C and N pools, and soil WEOC and HWEOC were significantly higher in the third month after biochar application than at other sampling times, whereas soil WETN and HWETN continuously increased from the third month and peaked in the ninth month after biochar application. Conclusions: Our results indicate that although biochar application consequently decreases labile pools on short timescales, it still highlights the potential to maintain stability of soil labile C and N pools in forest ecosystems in the short term. Our findings might further contribute to accelerating C sequestration and N cycles in low fertility soils and might ultimately be conducive to improving the adaptive capacity of vulnerable ecosystems in response to frequent prescribed burning and climate change. [ABSTRACT FROM AUTHOR]

Floodplain soils are subject to quasi-periodic flood disturbances. This flooding serves to enrich floodplain soils, increasing their fertility and often making them ideal locations for agriculture. However, what is less well understood is how the frequency of flooding impacts on soil fertility and the diversity of soil character. This study investigates how flood frequency influences the heterogeneity (assessed using 26 physical and geochemical soil properties) of floodplain soils in a semi-arid floodplain wetland system in New South Wales, Australia. The study includes an investigation of soil properties across four flood frequency (or disturbance frequency) categories ranging from frequent through to infrequent flood disturbance. Thirty samples were collected from each zone and the physical and geochemical soil data were analyzed using a suite of univariate and multivariate statistical tests. The results show that sites subject to an intermediate level of flood disturbance have a greater level of diversity in soil properties than those sites subject to frequent flood disturbances. These results reflect those of the Intermediate Disturbance Hypothesis, an ecological theory that posits the highest biological diversity will also be found in intermediately disturbed environments and suggests that there might be physical habitat drivers of biological diversity in intermediately disturbed floodplains. [ABSTRACT FROM AUTHOR]

Context: Improving the stability of legumes in grasslands in the face of variable seasonal conditions is key to mitigating risks posed by drought. Aims: We assessed the persistence of a range of legume species and cultivars in order to inform legume choice for pasture improvement and identify priority species for further development. Methods: Twenty field experiments in four series were conducted at sites with contrasting seasonal and soil characteristics in the 'high-rainfall' (560–920 mm long-term average) Tablelands and Monaro regions of New South Wales, Australia. Legumes were grown as pure swards and assessed periodically for seedling density, plant frequency and dry matter for up to 5 years. Key results: Legume dry matter production was positively correlated with plant frequency. However, most legumes persisted poorly at most sites, particularly on soils of lower fertility. Subterranean clover (Trifolium subterraneum) cv. Goulburn was the best performing cultivar of that species across sites on the Southern Tablelands and Monaro. Yellow serradella (Ornithopus compressus) cvv. Avila and Yellotas showed promising persistence, particularly under drought conditions. White clover (T. repens) was the most broadly adapted of the perennial legumes across a range of soils, but persistence was still inadequate at many sites. Lucerne (Medicago sativa) was approximately twice as productive as the next-most productive species when soil conditions suited its growth, but it failed to persist on acidic, low-fertility soils. Conclusions: Serradella species (yellow and French, O. sativus) and white clover, in conjunction with subterranean clover, offer the best near-term prospects for diversifying legume productivity and resilience under variable seasonal conditions in tableland environments. Implications: An increased focus on phenology and seed characteristics is suggested to improve the persistence of annual and facultative perennial legume species in grasslands. Serradella and white clover are identified as the highest priorities for cultivar development for tableland environments of south-eastern Australia. This study evaluated the stability and persistence of a range of legume species and cultivars to identify viable options for grasslands of south-eastern Australia. Yellow and French serradella, white clover and subterranean clover were identified as priority species because they are already, or are close to being, viable options for use in grasslands. An increased focus on phenology and seed characteristics is suggested to improve the persistence of white clover and serradella in grasslands. [ABSTRACT FROM AUTHOR]

The jarrah forest is a natural ecosystem with significant endemism in the flora and fauna. The forest stands on the western edge of the ancient Great Plateau of Western Australia on the granitic shield of the Yilgarn craton (2.5 Gya). The long-term migration of soluble iron and aluminium led to the formation of bauxite ore. The regolith ore is bound by surficial topsoil and deep pallid zone kaolinite clays, primarily used in land rehabilitation. We investigated the chemical fertility of the substrates, along with key physical properties. We found the capacity of these soils to provide a stable growth medium differed considerably in their ability to retain and supply nutrients. These substrates are deficient in nitrogen, phosphorus, and micronutrients. In the topsoil, 15% of total P is plant-available, while in the pallid zone layer, only 1% of total P is available. 31P-NMR showed no organic P in the pallid zone, whereas the topsoil had significant organic P and, consequently, a supply of phosphate ions. This shows the importance of organic P in the topsoil for ecosystem nutrition when inorganic fertilisers are not applied in state-of-the-art restoration schemes. [ABSTRACT FROM AUTHOR]

This review seeks to analyse and prioritise needs and gaps in research and development (R&D) for the north Australian beef cattle breeding industry, and to advise on options to increase rates of adoption and successful implementation of this R&D. The material reviewed includes the peer-reviewed literature as well as industry reports and other relevant publications in three targeted areas of R&D deemed to be important by industry leaders and supporting scientists: (i) breeding herd management, (ii) feedbase management, and (iii) management of environmental sustainability. For breeding herd management, the need for uniform definition and consistent utilisation of appropriate productivity metrics is highlighted, with emphasis on assessment of maternal reproductive efficiency in terms of weaning (or branding) rates. Priority is given to the urgent need for reliable means of remotely assessing causes of neonatal calf mortality to enable the development and application of management interventions that improve calf survival rates. The highest priority for feedbase management is to increase producer awareness and willingness to adopt stocking rates that are appropriately matched to the long-term carrying capacity of native rangeland pastures that predominate in northern Australia. Other opportunities include increasing the use of perennial, tropically adapted legumes, where conditions permit, to improve soil fertility and nitrogen intake of cattle, and devising strategies to overcome widespread phosphorus deficiency through diagnosis and supplementation, especially in the wet season. In order to enhance environmental sustainability in the face of climate change, priorities include improving producer awareness and use of increasingly robust tools for predicting key weather events, as well as developing genetic strategies to increase heat tolerance of cattle and evaluating management interventions to mitigate heat stress. Conclusions drawn from these sections are summarised and used to make recommendations on priorities for increasing adoption of existing research-proven practices and technologies, and for further R&D on selected topics. Beef cattle production is the most important agricultural sector in northern Australia. This review addresses concerns about the low rate of adoption of research-proven practices to improve reproductive performance in northern breeding herds. Needs and gaps in research and development are analysed, and options to increase adoption and implementation of research outcomes are recommended, in three targeted areas: breeding herd management, feedbase management, and management of environmental sustainability. [ABSTRACT FROM AUTHOR]

Purpose: A poor understanding of the nature of variation of soil properties within a field can lead to management decisions that reduce productivity or increase off-site environmental risks. Methods: The variability in total C%, total N%, plant-available (Colwell) P, and pH in CaCl2 at multiple depths is examined from two sites near Wagga Wagga and Yerong Creek in the mixed farming zone of southern New South Wales, Australia. The minimum number of cores required to estimate the mean for each soil property with a given level of precision (1%, 5%, and 10%) was determined and the distribution of the sample data was described by calculating the skewness and kurtosis. Results: The number of cores (42 mm diameter) required to estimate the mean was least for soil pH (3 cores) at both sites and greatest for Colwell P (25 and 58 cores) at a 10% precision in the surface 0.1 m of soil at the Wagga Wagga and Yerong Creek sites, respectively. The distributions of soil chemical properties were greatly varied with skewness and kurtosis both influencing the data. The mean value of the pH distributions sometimes exceeded the mode, leading to an underestimation of the extent of soil acidity. The mean value for Colwell P also often exceeded the mode, indicating an overestimate of the P status of the soil from a productivity perspective but concurrently underestimating the risk of off-site losses, associated with high P values at some locations. There was also an overestimation of the organic C fractions at these sites. Noteworthy in our data was a broad distribution across a large range in all soil parameters at the soil surface which, despite a generally normal distribution at that depth, gave a mean value that represents a relatively constrained approximation of the true fertility status of the soil. Conclusion: This study highlights the importance of understanding the nature of the variability in soil properties for interpreting soil test results appropriately for agronomic and environmental purposes. Due to its highly variable nature, Colwell P could not be reliably measured within the level of precision assumed under existing soil sampling guidelines used in Australia. [ABSTRACT FROM AUTHOR]

Context: The Brigalow Belt bioregion of central Queensland has been extensively developed for agriculture since exploration by Leichhardt in 1844. About 4.5 million hectares of vegetation dominated by brigalow (Acacia harpophylla) was cleared as part of the Land Development Fitzroy Basin Scheme, which commenced in 1962. When the Vegetation Management Act 1999 commenced, 93% of brigalow woodland had been cleared. Grazing is the dominant land use in the Fitzroy Basin, with 2.6 million cattle over 11.1 million hectares (72% of the catchment area). This is the largest cattle herd in any natural resource management region in Australia, accounting for 25% of the state herd and 11% of the national herd. Aims: The Fitzroy Basin, Queensland's largest coastal catchment, drains directly to the Great Barrier Reef, and as reef health continues to decline, there has been increased focus on the impacts of land-use change and grazing management on hydrology and runoff water quality. The Brigalow Catchment Study sought to determine the impact of land clearing, land-use change and land management on hydrology, soil fertility, water quality and animal production in the Fitzroy Basin. Methods: The study is a paired, calibrated catchment study. Catchment hydrology, soil fertility, water quality and agricultural productivity were monitored before and after land clearing and land-use change. Key results: The Brigalow Catchment Study has shown that clearing brigalow for grazing in the Fitzroy Basin doubled runoff, increased peak runoff rate by 50% and increased total suspended solid loads by 80%. Soil fertility and pasture productivity also declined under grazing compared with brigalow. Overgrazing exacerbated these results, as failure to reduce stocking rate with reduced pasture productivity more than tripled runoff, peak runoff rate and total suspended solid load compared with conservatively grazed pasture. Conclusions: This study demonstrates the impacts of land-use change and land management on hydrology, soil fertility and water quality. The long-term data records are a model in their own right, capable of answering land-use and land-management questions beyond the initial study scope. Implications: Sustainable grazing management should consider the production limitations of depleted soil and pasture resources to minimise land degradation. In the Brigalow Belt bioregion of Australia, clearing native vegetation for agriculture since the 1960s has altered hydrology and nutrient cycling over 36.7 million hectares. Long-term monitoring at the Brigalow Catchment Study has quantified changes in hydrology and soil fertility as a result of land-use change. Agricultural systems established soon after clearing were initially highly productive; however, productivity has since declined in accordance with declines in soil fertility. [ABSTRACT FROM AUTHOR]

Purpose: Owing to their topographic location and nutrient rich soils, riparian forests are often converted to pastures for grazing. In recent decades, remnant riparian forests cleared for grazing pastures have been restored with native species. The impacts of such land-use changes on soil fungal communities are unclear, despite the central roles that soil fungi play in key ecosystem processes. We investigated how soil fungal taxonomic and functional composition are affected by land-use change at different depths, and if variation in soil fungal communities is related to edaphic properties and extant vegetation. Methods: The study was conducted in six waterways in south-eastern Australia, each comprising three land-use types: remnant riparian forest, cleared forest converted to pasture, and pastures restored with native plants. We surveyed three strata of vegetation and sampled top-soil and sub-soil to characterise physicochemical properties and soil fungal communities. ITS1 region sequences were used to assign soil fungal taxonomic and functional composition. Results: Fungal taxonomic and functional composition infrequently varied with land-use change or soil depth. Overall, environmental properties (soil and vegetation) explained 35–36% of variation in both fungal taxonomic and functional composition. Soil fungal taxonomic composition was related to soil fertility (N, P, K, pH and Ca) and ground cover characteristics, whereas functional composition was related to clay content, sub-canopy cover and tree basal area. Conclusion: Across the six studied waterways, fungal taxonomic and functional composition were more strongly associated with land-use mediated changes in site-scale soil physicochemical properties and vegetation structure than broad-scale classes of land-use type. [ABSTRACT FROM AUTHOR]

1. Highly diverse plant communities growing on nutrient-impoverished soils are test beds for theories on species coexistence. Here, neighbouring mycorrhizal and non-mycorrhizal plants compete for limited phosphorus. The impact of belowground interactions on community dynamics is underexplored. 2. We used an experimental approach to investigate effects of inoculation with arbuscular mycorrhizal (AM) fungi and a phosphorus supply gradient on competitive and facilitative interactions among mixed assemblages of woody plants in microcosms. The plant species, one cluster root-forming (CR) species and four AM species, are native to jarrah forest that grows on nutrient-impoverished soils in south-western Australia. We measured plant growth in microcosms, with and without inoculation with the AM fungus Rhizophagus irregularis, and across a gradient of P supply: 0, 9, 27 and 243 mg P per kg of soil. 3. Our data show evidence of plant-plant facilitation at low P supply and competition at high P supply. Growth of the CR species, Hakea undulata, was highest in microcosms with 0P and without AM inoculation. One AM species, Bossiaea aquifolium, also performed better at lower P levels, possibly benefitting from P mobilised by H. undulata. The other three AM species, one strongly obligates, performed better at higher P levels. Data for Acacia celastrifolia suggested it was facultatively mycotropic, and because there was no correlation between AM colonisation and the relative inoculum effect, we suggest positive effects of AM inoculation at 9P might be due to benefits other than P acquisition, such as pathogen defence. Benefit of AM inoculation diminished for three of four mycorrhizal species at the highest P level as we had predicted. The fourth species, Eucalyptus marginata (jarrah), had higher growth in microcosms that were not inoculated with AM, perhaps because the species benefits more from ectomycorrhizas. 4. Synthesis. Our experimental data suggest spatial heterogeneity of soil P, coupled with a diversity of nutrient-acquisition strategies, and plasticity among plant-plant and plant-AM fungi interactions, contributes to plant species coexistence in the nutrient-impoverished jarrah forest. Our research highlights the importance of below-ground mechanisms for understanding factors determining community structure including a potential role of AM fungi in plant pathogen defence. [ABSTRACT FROM AUTHOR]

More than 10% of Australia's 49 M ha of grassland is considered degraded, prompting widespread interest in the management of these ecosystems to increase soil carbon (C) sequestration—with an emphasis on long‐lived C storage. We know that management practices that increase plant biomass also increase C inputs to the soil, but we lack a quantitative understanding of the fate of soil C inputs into different soil organic carbon (SOC) fractions that have fundamentally different formation pathways and persistence in the soil. Our understanding of the factors that constrain SOC formation in these fractions is also limited, particularly within tropical climates. We used isotopically labelled residue (13C) to determine the fate of residue C inputs into short‐lived particulate organic matter (POM) and more persistent mineral‐associated organic matter (MAOM) across a broad climatic gradient (ΔMAT 10°C) with varying soil properties. Climate was the primary driver of aboveground residue mass loss which corresponded to higher residue‐derived POM formation. In contrast, MAOM formation efficiency was constrained by soil properties. The differential controls on POM and MAOM formation highlight that a targeted approach to grassland restoration is required; we must identify priority regions for improved grazing management in soils that have a relatively high silt+clay content and cation exchange capacity, with a low C saturation in the silt+clay fraction to deliver long‐term SOC sequestration. [ABSTRACT FROM AUTHOR]

Over the last three decades, farming systems in Europe and Australia have seen a decline in legume plantings, leading to reduced soil carbon and fertility, and an increase in plant disease, reliance on industrial nitrogen fertilizer and herbicides. In Australia, one reason for this decline has been the movement towards sowing crops and forages into dry soil, before the opening rains, as a consequence of climate variability. This practice predicates against the survival of rhizobial inoculants, and hence generates uncertainty about legume performance. The research reported here was initiated to improve the robustness of a specific forage legume/rhizobia symbiosis to increase nitrogen fixation in low pH, infertile soils. Rhizobial strains (Rhizobium leguminosarum biovar viciae) from Pisum sativum L. were sourced from acid soils in southern Italy and southern Australia. Strains were evaluated for N fixation on the forage legumes P. sativum, Vicia sativa and Vicia villosa, then for survival and persistence in acid soils (pHCa 4.6). Fourteen of the strains produced a higher percentage of nitrogen derived from the atmosphere (%Ndfa) compared to commercial comparator strain SU303 (<78%). Twenty‐two strains survived sufficiently into the second season to form more nodules than SU303, which only achieved 3% of plants nodulated. Elite strains WSM4643 and WSM4645 produced six times more nodulated plants than SU303 and had significantly higher saprophytic competence in acid soil. These strains have the ability to optimize symbiotic associations with field peas and vetch in soils with low fertility, carbon and pH that are restrictive to the current commercial strain SU303. [ABSTRACT FROM AUTHOR]

Classical reductionist experimentation tends to conceptually compartmentalise mitigation and adaptation into binary categories, shielding insight into how greenhouse gas (GHG) emissions and climate change interact. Here, our primary aim was to examine how a key tenant of the global climate crisis – drought – is likely to influence soil organic carbon (SOC). We deconstruct these paradigms using case study farms in Tasmania, Australia, using state of the art models to simulate pasture production and SOC under historical and 2050 climates, the latter encapsulating more frequent extreme weather events. We show that longitudinal changes in SOC stocks correlate positively with standard precipitation evapotranspiration index (SPEI) via the mediating effects of seasonal pasture growth. Drought elicited notable SOC losses, particularly when antecedent SOC stocks were high, whereas high rainfall years amplified SOC sequestration. Renovating pastures with perennial legumes enhanced sequestration under 2050 climates, as did introducing irrigation and increasing soil fertility. In most cases however, the influence of aridity on SOC dominated over that of farm management, suggesting that climate change - and by extension, seasonal rainfall distribution - are likely to engender greater influence on SOC stocks compared with farm management or practice change. As such, aspirations to maintain SOC stocks at ceiling levels over the long-term are likely to be challenged by the changing climate and particularly drought. Even so, we contend that adoption of practices aimed at improving soil organic matter can benefit productivity through enhancement of soil fertility, water-holding capacity and health, and as such should be encouraged, particularly where status quo agro-ecosystems are degraded. • We explored how soil organic carbon (SOC) stocks are influenced by drought. • High seasonal rainfall was conducive to improved SOC sequestration. • Drought elicited high SOC losses, particularly when antecedent SOC stocks were high. • Deep-rooted perennials, additional irrigation and fertiliser improved SOC accrual. • SOC accrual was greatest for zones with degradation and/or suboptimal productivity. [ABSTRACT FROM AUTHOR]

Bogong Moths Agrotis infusa and their summer sub-adult migration (up to 1000 km) to the Alps is an important natural and cultural (Indigenous and European) phenomenon in south-east Australia. In Victoria, high elevation rock outcrops and peri-glacial boulder fields are favoured aestivation sites for the moths. A variety of mammalian and avian predators exploit this nutrient rich food source. The summer of 2017 saw an unprecedented collapse in the annual numbers of moths migrating to the Alps. They have not returned in large numbers everywhere. Investigations into the Mountain Pygmy-possum Burramys parvus included a study of the contribution of A. infusa to boulder field habitats in Victoria (basalt) and NSW (granite). Standardised soil and litter samples (n= 132) were collected in three altitude bands and from eastern and western aspects. Agrotis infusa favoured high altitude westerly slopes and there was a very high correlation with B. parvus abundance (R= 0.9087). Primary and secondary bio-transport of A. infusa (remains and guano) make a significant contribution to alpine food chains, nutrient dispersal and soil fertility. These data and 40 years of annual observations that include the recent population collapse have dramatic implications for the alpine environment. No gross environmental changes that may have been adverse to Agrotis infusa have been observed at alpine aestivation sites, strongly suggesting unprecedented detrimental change (climate or human-induced) across its natal areas in south-east Australia. Apart from severe drought, we suspect adverse land-use changes, including increased use of neonicotinoids. Systematic and robust monitoring and research into this continental-scale collapse of the Bogong Moth is urgently required. [ABSTRACT FROM AUTHOR]

Background and aims Little is known about the evolutionary and ecological drivers of carnivory in plants, particularly for those terrestrial species that do not occur in typical swamp or bog habitats. The Mediterranean endemic Drosophyllum lusitanicum (Drosophyllaceae) is one of very few terrestrial carnivorous plant species outside of Australia to occur in seasonally dry, fire-prone habitats, and is thus an ecological rarity. Here we assess the nutritional benefits of prey capture for D. lusitanicum under differing levels of soil fertility in situ. Methods We measured the total nitrogen and stable nitrogen and carbon isotope ratios of D. lusitanicum leaves, neighbouring non-carnivorous plant leaves, and groups of insect prey in three populations in southern Spain. We calculated trophic enrichment (ε 15N) and estimated the proportion of prey-derived nitrogen (%Nprey) in D. lusitanicum leaves, and related these factors to soil chemistry parameters measured at each site. Key results In all three populations studied, D. lusitanicum plants were significantly isotopically enriched compared with neighbouring non-carnivorous plants. We estimated that D. lusitanicum gain ~36 %Nprey at the Puerto de Gáliz site, ~54 %Nprey at the Sierra Carbonera site and ~75 %Nprey at the Montera del Torero site. Enrichment in N isotope (ε 15N) differed considerably among sites; however, it was not found to be significantly related to log10(soil N), log10(soil P) or log10(soil K). Conclusions Drosophyllum lusitanicum individuals gain a significant nutritional benefit from captured prey in their natural habitat, exhibiting proportions of prey-derived nitrogen that are similar to those recorded for carnivorous plants occurring in more mesic environments. This study adds to the growing body of literature confirming that carnivory is a highly beneficial nutritional strategy not only in mesic habitats but also in seasonally dry environments, and provides insights to inform conservation strategies for D. lusitanicum in situ. [ABSTRACT FROM AUTHOR]

Those not immediately involved in managing a dryland farm sustainably in a risky water-limited environment such as Australia may think a comparison with rocket science a bit of a stretch. But if the level of challenge, the importance to humanity, the long-term multidisciplinary team approach and planning required, and the level of uncertainty inherent in the pursuit are measures, then I think the comparison is warranted. The importance of the farming systems agronomy research that has supported agriculture and food security in Australia and globally since William Farrer's time perhaps receives less public attention than some other science areas such as genetics, genomics, or digital agriculture—indeed, agriculture is now literally "rocket science" as satellite-guided machines and sensors gather volumes of data about the soils, plants, and weather on farms at scales and speeds hitherto impossible. Yet despite spectacular advances in individual genetic or management technologies, few have been singularly transformational. Rather significant productivity improvements generally arise when a combination of technologies, often old and new are integrated and synergize in specific ways within a system—a process here termed incremental transformation. William Farrer himself was clearly aware of this fact, as this article shows, he placed as much importance on maintaining the fertility of the soil in which he grew wheat as on improving the wheat plant itself. This article first provides some background to Farrer and on his interests in Genotype × Environment × Management (G × E × M) interactions (though he certainly did not use that terminology). It then describes some examples from my own research teams, to demonstrate the ongoing impact that arises from research to capture synergies from new genetics and improved management in the pursuit of incremental transformation. [ABSTRACT FROM AUTHOR]

The Australian grains industry relies on mineralized nitrogen (N) from soil organic matter and plant residues, but fertilizer N is increasingly needed to optimize yields. Most farmers are guided on N fertilizer requirements by commercial crop advisors. We surveyed (n = 132) and interviewed (n = 11) New South Wales grains advisors to gauge the usage of soil process understanding, soil data and decision support systems (DSSs) when developing N recommendations. Soil moisture at sowing, seasonal forecasts, crop rotation, soil mineral N, financial risk profiles and paddock history were all used to prepare N fertilizer advice, but stored soil moisture was most important. Farmer confidence in soil N testing was low due to high spatial variability. Most advisors calculated N fertilizer required for yields within 10%–15% of crop potential, but clients' attitude to financial risk guided final N recommendations. Conservative growers preferred a low input system, while more reliable rainfall or greater reliance on stored soil water led growers to apply higher N rates to maximize long‐term profits. Advisors preferred "rules‐of‐thumb," simple DSSs and knowledge of crop growth, to elaborate DSSs requiring detailed inputs and soil characterization. Few used in‐crop N sensing. N decision methodologies need to be updated to account for changes in soil fertility, cropping systems and farming practices. New research is needed to answer practical questions regarding soil N mineralization and N losses associated with alternative N application practices and extreme weather events. Training of new advisors in N processes and DSS use needs to be ongoing. [ABSTRACT FROM AUTHOR]

Intercropping cereals with legumes can potentially enhance productivity and soil fertility. There is limited experimental evidence on the mechanisms underlying benefits or risks in intercropping systems and below-ground interactions in intercrops remain largely unstudied. Such understanding can inform strategies towards maximising returns to investments, particularly in poor fertility soils on smallholder farms in semi-arid areas of sub-Saharan Africa. Additive intercropping experiments were established covering several seasons (2010/11–2014/15) and different conditions (on-station and on-farm) to determine effects on soil chemical variables, root dynamics and yield of intercrops. Maize was planted with the first effective rains and received either no fertiliser or 40 kg N ha −1 . Cowpea was planted on the same date as maize or three weeks after planting maize in intercrops or sole stands and received no fertiliser. End-of-season available N was highest ( P < 0.05) under the late planted intercrop with 40 kg N ha −1 treatment in 2013/14. Addition of 40 kg N ha −1 significantly increased maize grain yield by 500–1100 kg ha −1 in the 2013/14 season. There was generally greater productivity and over-yielding in the intercrops compared with the sole crops; most intercrops had a land equivalent ratio >1. Intercropping, however, resulted in compromised cowpea yields especially under the relay intercrop compared with the sole cowpea stands whilst maize yield was either not affected or improved. We attributed this to the lack of below-ground niche differentiation in root distribution between maize and cowpea. Maize–cowpea intercropping with low doses of N fertiliser resulted in over-yielding compared with monocropping. Intercropping proved to be a robust option across seasons and soil types, confirming that it is a promising option for resource-poor smallholders. [ABSTRACT FROM AUTHOR]

Healthy, fertile soil is the material of life itself. It is chemically, biologically and physically structured to support the growth of healthy, environmentally sustainable foods. Recent years have seen a resurgent focus on soil science in Australia. Yet, the influence of soil in the politics of food systems has received comparatively little attention, despite long awareness in farming communities of how the natural world shapes farmers’ choices and possible actions. Drawing on work with SoilCare, a Landcare group with a focus on soil processes in the Northern Rivers of New South Wales, this paper explores the usefulness of approaching soil as an actor in food systems. Taking a participatory approach, and drawing on recent work on new materialisms, we argue that soil can be understood as an important ally in the struggle to shape a just and sustainable food system. While this work is intended to test this idea through a modest local case study, it may point to important new avenues for investigation in food politics. [ABSTRACT FROM PUBLISHER]

Aim We investigated how the probability of burning is influenced by the time since fire ( TSF) and gradients of climate, soil and vegetation in the fire-prone mediterranean-climate mallee woodlands of south-eastern Australia. This provided insight into the processes controlling contemporary fuel dynamics and fire regimes across biogeographical boundaries, and the consequent effects of climate change on potential shifts in boundaries between fuel systems and fire regimes, at a subcontinental scale. Location South-eastern Australia. Methods A desktop-based GIS was used to generate random sampling points across the study region to collect data on intersecting fire interval, rainfall, vegetation and soil type. We used a Bayesian framework to examine the effects of combinations of rainfall, vegetation and soil type on the hazard-of-burning and survival parameters of the Weibull distribution. These analyses identify the nature of environmental controls on the length of fire intervals and the age-dependence of the hazard of burning. Results Higher rainfall was consistently associated with shorter fire intervals. Within a single level of rainfall, however, the interaction between soil and vegetation type influenced the length of fire intervals. Higher-fertility sands were associated with shorter fire intervals in grass-dominated communities, whereas lower-fertility sands were associated with shorter fire intervals in shrub-dominated communities. The hazard of burning remained largely independent of TSF across the region, only markedly increasing with TSF in shrub-dominated communities at high rainfall. Main conclusions Rainfall had a dominant influence on fire frequency in the mediterranean-climate mallee woodlands of south-eastern Australia. Predicted changes in the spatial distribution and amount of rainfall therefore have the potential to drive changes in fire regimes, although the effects of soil fertility and rainfall on fire regimes do not align on a simple productivity gradient. Reduced soil fertility may favour plant traits that increase the rate of woody litter fuel accumulation and flammability, which may alter the overriding influence of rainfall gradients on fire regimes. [ABSTRACT FROM AUTHOR]

Boron (B) deficiency frequently occurs on soils that are low in organic carbon (C) (<1.0% organic C), pH (soil pHCa<5.0), and clay content (<5% clay). Acid sands with these soil properties are common in south-western Australia (SWA). Moreover, hot calcium chloride (CaCl2) extractable B levels are commonly marginal in the acid sands of SWA. This study examined the effects of soluble and slow release soil-applied B fertilizer and foliar B sprays on crops most likely to respond to B fertilizer on these soils, canola (oil-seed rape,Brassica napusL.) and lupin (Lupinus angustifoliusL.). At 25 sites over three years, canola was grown with (0.34 kg ha-1) or without B applied as borax [sodium tetraborate decahydrate (Na2B4O7·10H2O) 11% B], and this was followed by nine experiments with B rates [0, 0.55, 1.1 kg ha−1, applied as borax or calcium borate (ulexite, NaCaB5O6(OH)6·5(H2O), 13% B] and foliar sprays (0.1% solution of solubor, 23% B) in 2000–2001. A further five sites of B rates and sources experiments were carried out with lupin in 2000–2001. Finally, foliar B sprays (5% B w/v as a phenolic complex) at flowering were tested on seven sites in farmers’ canola crops for seed yield increases. No seed yield increases to soil-applied B were found while foliar B application at flowering increased canola seed yield in only one season across seven locations. By contrast, borax fertilizer drilled with the seed at sowing decreased canola seed yield in nine of 34-farm sites, and decreased lupin yield in two of five trials. Toxicity from drilled boron fertilizer decreased yield could be explained by decreases in plant density (by 22–40%) to values lower than required for optimum seed yield. Seedling emergence was decreased by borax applied at sowing but less so by calcium borate. Foliar B spray application never reduced seed yield due to toxicity effects. Boron fertilizer drilled with the seed increased the B concentration in plant dry matter at early to mid-flowering. Boron application decreased the oil concentration of grain of canola at four sites. The oil yield of canola was significantly decreased at seven sites. Notwithstanding the marginal B levels on acid sands of the SWA region, care needs to be taken on use of borax fertilizer as toxicity was induced in canola and lupin; with 0.34 to 1 kg B ha−1(3-10 kg borax ha−1) at sowing depressing seed yield, mostly by decreasing plant density. Rather than making general recommendation for B fertilizer application based on 0.01M CaCl2soil extractable B, soil and plant analysis should be used to diagnose B deficiency and B fertilizer use limited to calcium borate or foliar borax rather than soil-applied borax on low B sands. [ABSTRACT FROM AUTHOR]

We present a conceptual model linking dry-mass allocational allometry, hydraulic limitation, and vertical stratification of environmental conditions to patterns in vertical tree growth and tree height. Maximum tree height should increase with relative moisture supply and both should drive variation in apparent stomatal limitation. Carbon isotope discrimination (∆) should not vary with maximum tree height across a moisture gradient when only hydraulic limitation or allocational allometry limit height, but increase with moisture when both hydraulic limitation and allocational allometry limit maximum tree height. We quantified tree height and ∆ along a gradient in annual precipitation from 300 to 1600 mm from mallee to temperate rain forest in southeastern Australia; Eucalyptus on this gradient span almost the entire range of tree heights found in angiosperms worldwide. Maximum tree height showed a strong, nearly proportional relationship to the ratio of precipitation to pan evaporation. ∆ increased with In P/Ep, suggesting that both hydraulic limitation and allocational allometry set maximum tree height. Coordinated shifts in several plant traits should result in different species having an advantage in vertical growth rate at different points along a rainfall gradient, and in maximum tree height increasing with relative moisture supply, photosynthetic rate, nutrient supply, and xylem diameter. [ABSTRACT FROM AUTHOR]

During revegetation, the maintenance of soil carbon (C) pools and nitrogen (N) availability is considered essential for soil fertility and this study aimed to evaluate contrasting methods of site preparation (herbicide and scalping) with respect to the effects on soil organic matter (SOM) during the critical early establishment phase. Soil total C (TC), total N (TN), hot-water extractable organic C (HWEOC), hot-water extractable total N (HWETN), microbial biomass C and N (MBC and MBN), total inorganic N (TIN) and potentially mineralizable N (PMN) were measured over 53 weeks. MBC and MBN were the only variables affected by herbicide application. Scalping caused an immediate reduction in all variables, and the values remained low without any sign of recovery for the period of the study. The impact of scalping on HWETN and TIN lasted 22 weeks and stabilised afterwards. MBC and MBN were affected by both herbicide and scalping after initial treatment application and remained lower than control during the period of the study but did not decrease over time. While scalping had an inevitable impact on all soil properties that were measured, that impact did not worsen over time, and actually improved plant growth (unpublished data) while reducing site establishment costs. Therefore, it provides a useful alternative for weed control in revegetation projects where it is applied only once at site establishment and where SOM would be expected to recover as canopy closure is obtained and nutrient cycling through litterfall commences. [ABSTRACT FROM AUTHOR]

Abstract: Environmental factors such as parent material and climate can have a large effect on total carbon concentration and soil carbon stocks, yet unlike vegetation type, fertiliser use and grazing pressure, these cannot be changed by management. The relative effects of these environmental and land management factors were compared in the Monaro and Boorowa regions of New South Wales (NSW), Australia. Parent material, geographic region, soil depth and soil fertility had a significant influence on soil carbon stocks to 0.70m while pasture type (introduced vs native pastures) did not. Parent material and soil depth significantly (P <0.05) influenced the mean soil carbon stock (Mg C/ha) in the Monaro region; 159 (11 se) in basalt-derived soils, 77 (11 se) in deep granite-derived soils and 43 (3 se) in shallow granite-derived soils. Climate also significantly (P <0.05) influenced the mean carbon stock, with deep granite-derived soils in the Monaro region having 76.5 (11 se) compared with 51.8 (3 se) Mg C/ha in the Boorowa region. A considerable proportion of the total carbon stock to 0.70m for all sites was measured in the subsoil (0.30 to 0.70m). In the Monaro region, basalt-derived soil contained 43% of the total carbon stock in the subsoil, compared with 28% in deep granite and shallow granite-derived soil. In the Boorowa region, deep granite-derived soil contained 33% of the total carbon stock in the subsoil. Restricting soil carbon measurements to the surface 0.30m of soil may result in erroneous conclusions with respect to the influence of land management on the accumulation of carbon in soil. Total carbon concentration was positively correlated with labile carbon, total nitrogen, cation exchange capacity and extractable sulfur, suggesting that for a given parent material and climate, maintaining adequate pasture nutrition may substantially increase soil carbon stocks. [Copyright &y& Elsevier]

Purpose:Many farmers remain hesitant to implement structured management plans and strategies tailored to address soil health, irrespective of mounting scientific evidence for the credibility of certain soil health indicators, an increase in the reporting of program benefits and progress in communicating these benefits. Hence, the purpose of this research is to better understand the impediments associated with the adoption of such programs. Design:Non-parametric analysis of a mail-based survey supported with content analysis of landholder comments was used. Findings:This research highlights that impediments to the adoption of soil health programs are affected by region and that this is likely influenced by the availability, enthusiasm and motivation of surrounding environmental service providers. While the initial investment in soil health management is perceived as an impediment, landholders indicate that production longevity and long-term financial gain are achievable. Education is not viewed as an impediment by landholders, but cannot be ruled out as an impediment due to the increasing complexities of farming and the displayed knowledge of landholders. Practical implications:Impediments and incentives to the adoption of soil health management plans have been identified. This provides for strategic planning in promotion and adoption of such plans, as well as identifying priority issues of concern. Originality/Value:In investigating the impediments and incentives associated with adoption of soil health management plans, strategies for adoption can be formulated and pressing areas of concern are identified. [ABSTRACT FROM AUTHOR]

Two experiments were conducted to determine the establishment success of reintroducing Microlaena stipoides (pātītī, weeping rice grass) into existing high-fertility grassland on the volcanic cones of the Auckland Isthmus. The first experiment monitored the survival and development of juveniles planted in a factorial design including two planting densities, two slope classes and two aspects across three cones. Plant survival during establishment was consistently over 90%. Maximum M. stipoides cover after 2 years (>80%) was achieved on north-facing steep slopes (>25°) at the greater planting density (40 plants/m2). However, results were particularly idiosyncratic to specific cone/topographical combinations. The second experiment, on a flat site on one cone, monitored the survival and development of juveniles planted across four post-planting treatments designed to suppress resident vegetation recovery. Plant survival after 6 months was relatively low (50%), and none of the treatments achieved greater than 5% cover of M. stipoides after 1 year. The chosen post-planting treatments were unable to suppress vigorous recovery of competitive exotic grasses on a moist fertile site. Overall, juvenile planting was shown to be a potentially successful method of Microlaena establishment and could restore indigenous dominance to exotic grassland in this environment, but individual site factors and the high cost of establishment must be considered. [ABSTRACT FROM AUTHOR]

Many diagnostic soil-testing services only use measures of extractable and/or exchangeable potassium (exchangeable K) to provide guidance on the need or otherwise for applications of K fertilizer. Less commonly, soil tests for nonexchangeable, plant-available K are included, although this combination of soil K tests does not unequivocally detect situations where soil total K reserves are critically low. This article provides examples of how atom ratios between measured values of total K and exchangeable K in soils can alert crop advisors and growers of such situations. Specifically, total K / exchangeable K ratios at different depths in samples (136 sites) from canelands of northeastern Australia and from cropping lands (67 samples) in Fiji were found to vary from around 1.0 to 1,235. Lowest total K / exchangeable K ratio values were commonly recorded in soils from the Bundaberg/Maryborough region of northeastern Australia and from highly weathered ferruginous latosols supporting “talasiga” vegetation in Vanua Levu, Fiji. The Vanua Levu soils contained much lower total K reserves than did cropping soils near Nadi on Viti Levu. Summary details of total K / exchangeable K ratios for the five cane-growing regions of northeastern Australia are provided, together with soil K data to 800–900 mm in selected soils from the Fijian Islands. There is need to seriously consider additions of plant-available K when levels of exchangeable K are at or below accepted “critical levels” and corresponding total K / exchangeable K ratios are around <2 to 3. Total K and exchangeable K in the soils tested were not intercorrelated. [ABSTRACT FROM AUTHOR]

Twenty-four sites in northern Tasmania on Ferrosols formed on Tertiary basalt were sampled in 1997, 2005, and 2010. The farming systems at the sites during this period were either (a) continuous pasture, (b) continuous cropping of vegetable, cereal, and other cash crops in rotation, or (c) a mix of pasture and cropping (intermittent cropping). Average organic carbon (OC) concentrations across all sites and both sample depths (0–150 mm and 150–300 mm) decreased from 4.0% in 1997 to 3.5% in 2005 and 3.3% in 2010 (P< 0.001). Average OC was greater at 0–150 mm (4.1%) than at 150–300 mm (3.1%) (P< 0.001). Average total soil nitrogen (N) in 2010 (0.42%) at 0–150 mm was not significantly different (P = 0.07) from the average in 1997 (0.38%). Soil pH in water (pHw) showed the opposite trend to OC, increasing with time from 6.0 in 1997 to 6.2 in 2010. This reflects the consistent use of calcite and dolomite in Tasmanian farming because the natural pHwof these soils is less than 5.5. Exchangeable calcium and magnesium were also greater in 2010 compared with 1997. Bicarbonate-extractable phosphorus (P) averaged across both depths increased (P< 0.001) steadily from 77 mg kg−1in 1997 to 95 mg kg−1in 2005 to 126 mg kg−1in 2010. At the five sites that remained under continuous cropping throughout the study, average 2010 OC in the topsoil was 3.2%, a decrease of 0.5% since 1997; pHwwas unchanged at 6.4; and bicarbonate-extractable P increased by an average of 73 mg kg−1to 211 mg kg−1. For the three sites that remained in pasture the corresponding topsoil changes were 0.3% less OC to an average of 4.8%; pHw0.4 units greater at 6.0; and 41 mg kg−1more bicarbonate-extractable P to an average of 99 mg kg−1. At the six sites converted from continuous pasture to intermittent cropping the average 2010 topsoil OC was 4.5%, a loss of 1.3%; pHwincreased by 0.5 units to 6.1; and bicarbonate-extractable P increased by 35 mg kg−1to 97 mg kg−1. There was a highly significant (R2= 0.82) exponential relationship between topsoil OC in 2010 and the number of years each site had been cropped during the 38 years 1972–2010, for which reliable records were available (OC = 4.933e−0.018years), which suggested an equilibrium topsoil OC concentration of about 2.5% under continuous cropping on these soils. These results indicate that Tasmanian farmers on Ferrosols continue to increase the pHwand P fertility of their soils and that increasing cropping intensity on these soils comes at the expense of soil carbon. [ABSTRACT FROM AUTHOR]

Abstract: The Ernest Henry Mine in north west Queensland, Australia, is required to return disturbed land to native grassland and has been undertaking extensive revegetation of waste rock dumps since 2002. To ascertain the trajectories for revegetation success of these rehabilitated native grasslands, annual vegetation monitoring of both rehabilitation sites and selected reference areas has been undertaken since 2007. Long-term monitoring efforts have included assessments of vegetation composition, ecological structure and function at four rehabilitation areas (1–7 years post-rehabilitation) and proximal reference sites within surrounding grazed and ungrazed agro-ecosystems, undisturbed by mining. Our findings demonstrated that the oldest rehabilitated sites had similar species composition and functional elements to selected reference sites, although plant cover and biomass (particularly of native grasses) was lower than both grazed and ungrazed reference areas. The youngest sites had little established vegetation, however species richness was similar to the reference sites and functional life forms were present despite being in very low abundance. It is suggested that future monitoring events and informed management inputs (which consider local climatic conditions and soil fertility factors) could contribute to the development of a stable and sustainable native grassland thus achieving the desired end land use on these post-industrial landscapes. [Copyright &y& Elsevier]

Abstract: The soil nutrient status (0–10cm) of two farming systems (organic (OF) and conventional or integrated (CF) vegetable farms) at three locations (Gatton, Stanthorpe and Dorrigo) was examined for the suite of fertility indicators. A wide range chemical parameters and microbial biomass carbon were similar between farming systems, in contrast to some broad-acre organic systems. Examination of farm management records revealed substantial overlap between nutrient inputs at all localities with CF systems also receiving organic inputs, e.g. green manure and composts. Labile soil phosphorus levels were high (>100mgkg−1) in both farming systems, at all sites. The nutrient levels of these intensive vegetable production systems revealed potential environmental risks especially in sandy well drained soils and should be monitored accordingly. Future research could be focused on crop management measures to mitigate runoff and deep drainage loss of nutrients from these farms. [Copyright &y& Elsevier]

The prototype Spatial Optimizer 1.0 program for allocation of commodity production is demonstrated to show its potential as a decision support aid for policy making. The case study involves a set of agricultural commodities in south eastern Australia and the program uses estimates of each grid cell's soil suitability for each of the eight crops, both in the year 2000 and in the year 2050, by which time soil characteristics are expected to have been affected by environmental change. We first predict how much total regional production will result from a judicious re-location of commodity types, both under conditions of complete flexibility and when constrained by more realistic, upper and lower limits on production, and we compare such predictions with current production levels. We also estimate potential total regional revenue, both in the short term when current prices are assumed to remain static and in the long term when prices are assumed to change according to how much of each commodity is produced compared to its current output level, and we compare these results with current agricultural revenue. Our long-term estimates are based on year 2000 soil-suitability values and then on year 2050 soil-suitability values in order to gauge the probable impacts of environmental change. Finally, we run the 2050 simulation twice more, with one of the recommended, dominant crops removed in each instance. This generates maps of some localised concentrations of other commodities that will become necessary in the future if maximum revenue is to be retained after one of the more lucrative crops is discontinued. [ABSTRACT FROM AUTHOR]

Abstract: The conservation farming systems coupled with stubble retention are now widely adopted in southern Australia to improve soil fertility. However, little information is available about the effects of winter crops on soil labile organic carbon (C) and nitrogen (N) pools, especially in an arid agricultural ecosystem. In this study, eight winter cover crop treatments were used to investigate their effects on soil labile organic C and N pools and microbial metabolic profiles and diversity in temperate Australia. These treatments included two legume crops (capello woolly pod vetch and field pea), four non-legume crops (rye, wheat, Saia oat and Indian mustard), and a mixture of rye and capello woolly pod vetch as well as a nil-crop control. At the crop flowering stage, soil and crop samples were collected from the field and we examined aboveground crop biomass, soil NH4 +-N, NO3 −-N, extractable organic C (EOC) and N (EON) concentrations using methods of 2M KCl and hot water, microbial biomass, biologically active organic C (CBio), and substrate-induced respiration (SIR) using the MicroResp method. Results showed that the crop treatments had lower soil moisture content, NO3 −-N and the ratios of EOC to EON, but higher pH, NH4 +-N, EOC, EON, CBio, microbial metabolic diversity index (H) and evenness index compared with the control. There were no significant differences in microbial biomass C and N among the treatments. Although no pronounced differences in EOC and EON concentrations were found between the legumes and non-legumes, the legume treatments had lower SIR and higher H than the non-legume treatments. Principal component analysis showed that soil microbial metabolic profiles under the crops were different from those of the control, and the crop treatments had a clear separation along principal component 2. In addition, redundancy analysis showed that soil pH and moisture content were the most important influencing factors, along with EON and crop biomass, determining the patterns of microbial metabolic profiles under the crops. [Copyright &y& Elsevier]

The ancient landscape of the South - West Australian Floristic Region (SWAFR) is characterized by exceptional floristic diversity, attributed to a complex mosaic of nutrient - impoverished soils. Between - soil type differences in nutrient availability are expected to affect floristic assemblage patterns in the SWAFR. We compared patterns of floristic diversity between open - forest samples from three soil types in the high - rainfall zone of the SWAFR. The importance of environmental and spatial factors for species compositional turnover within soil types were evaluated within canonical correspondence analyses using variation partitioning. Patterns of phylogenetic diversity and dispersion were contrasted between soil types and related to differences in soil nutrient availability. Between - quadrat shared phylogenetic branch length for individual life form categories was correlated with explanatory variables using Mantel tests. Species and phylogenetic diversity increased with a decline in soil nutrients and basal area. Nutrient - poorer soils were differentiated by higher species density and phylogenetic diversity, and larger phylogenetic distances between species. Species turnover was best explained by environmental factors when soil nutrient concentrations and basal area were low. Coastal and inland quadrats from the most fertile soil type were distinguished by significantly differing patterns of phylogenetic diversity. Inland quadrats were characterized by strong relationships between phylogenetic diversity and environment, while phylogenetic patterns remained largely unaccounted for by explanatory variables within coastal quadrats. Phylogenetic diversity was more strongly related with environment within upland landform types for nutrient-poor soils. We highlight the complex relationships between climatic and edaphic factors within the SWAFR, and propose that the occurrence of refugial habitat for plant phylogenetic diversity is dynamically linked with these interactions. Climate change susceptibility was estimated to be especially high for inland locations within the high - rainfall zone. Despite the strong relationship between floristic diversity and soil fertility, holistic conservation approaches are required to conserve the mosaic of soil types regardless of soil nutrient status. [ABSTRACT FROM AUTHOR]

Biosolids were applied to a pasture and a vineyard in south-eastern Australia. At both sites, soil Cd, Cu, and Zn concentrations linearly increased with biosolids application rates although not to the extent of exceeding soil quality guidelines. Biosolids marginally increased soil C and N concentrations at the pasture site but significantly increased P concentrations. With lower overall soil fertility at the vineyard, biosolids increased C, N, and P concentrations. At neither site did biosolids application affect soil microbial endpoints. Biosolids increased pasture production compared to the unfertilised control but had little effect on grape production or quality. Interestingly, over the 3-year trial, there was no difference in pasture production between the biosolids treated plots and plots receiving inorganic fertiliser. These results suggest that biosolids could be used as a fertiliser to stimulate pasture production and as a soil conditioner to improve vineyard soils in this region. [ABSTRACT FROM AUTHOR]

The occurrence of tree deaths in young, 3 to 6 year old Eucalyptus globulus plantations established on farmland in south-western Australia was found to be strongly related to factors indicative of poor soil water storage capacity. Seven years after planting tree survival was significantly less on soils <2 m deep compared to >2 m deep (22% vs 70%). This is due to the limited ability of some soils to store a sufficient proportion of the annual rainfall within the root-zone to meet the plant water demand in a region with a recurrent annual summer drought. There are practical difficulties in routinely surveying soils to depths in excess of 2 m over broad areas, to predict the likelihood of tree death. On the granitic basement rocks of south-west Western Australia, the occurrence of ferricrete gravels provides a useful surrogate indicator for the presence of deeper soils. In this region the distribution of soil depth and soil fertility has a geomorphic basis, being related to previous patterns of deep weathering and regolith stripping. Soils have developed on various horizons of deeply weathered profiles, formed from granites and gneisses. These materials have been stripped to a variable extent by erosion, leading to a range of soil depths. The original weathered profiles, which correspond to the soils with ferricrete gravels, comprise the deepest soil/regolith materials (~30-50 m deep); whereas along drainage lines the regolith has been completely stripped, the soils are shallow and plantations are most susceptible to drought. Knowledge of the relationship between soil depth and plantation performance allows regional indications of drought risk to be developed from regional soil mapping and the production of more efficient sampling designs for site assessment. [ABSTRACT FROM AUTHOR]

The article discusses the effects of fire frequency and mowing on a temperate, derived grassland soil in south-eastern Australia. The research studied the following queries: how frequent fire leads to depletion of topsoil nutrient stores; does lack of disturbance promotes release of soil available nutrients through sward decline; does soil surface condition and biological activity decline under frequent burning; and does the effects of mowing are comparable with effects of fire. The study focuses on the thought that frequent disturbances such as fire are widely considered important drivers of plant composition and diversity in productive grassy ecosystems.

Liquid polyphosphate fertilizers have shown significant yield increases compared with granular orthophosphate fertilizer on highly P-fixing soils in Australian cropping trials. Polyphosphate fertilizers contain mixed P species (predominantly pyrophosphate and orthophosphate) and are therefore chemically different from most other inorganic P fertilizers, which contain only orthophosphate. To determine the mechanisms causing the yield responses to polyphosphate fertilizer, a method for investigating the isotopic exchangeability (lability) of P added as pyrophosphate was developed and tested. This method enabled the quantification of the hydrolysis reaction of pyrophosphate to orthophosphate in soil solution. As the rate of pyrophosphate applied increased, the proportion of pyrophosphate added that was isotopically exchangeable increased, and the percentage of pyrophosphate added that hydrolyzed to orthophosphate decreased. The method was further developed to test the hypothesis that pyrophosphate addition to soil may cause the mobilization of native orthophosphate reserves. The results suggested that there was no mobilization of native P after 7 d of incubation in two calcareous soils. [ABSTRACT FROM AUTHOR]

Modelling for the conservation of koala ( Phascolarctos cinereus) populations has primarily focused on natural habitat variables (e.g. tree species, soil types and soil moisture). Until recently, limited consideration has been given to modelling the effects of the landscape context (e.g. habitat area, habitat configuration and roads). Yet, the combined influence of natural habitats and anthropogenic impacts at multiple spatial scales are likely to be important determinants of where koala populations occur and remain viable in human-modified landscapes. The study tested the importance of multiscale habitat variables on koala occurrence in Ballarat, Victoria, Australia. The models focused at three spatial scales: site ( < 1 ha), patch (1–100 ha), and landscape (100–1000 s ha). Logistic regression and hierarchical partitioning analyses were used to rank alternative models and key explanatory variables. The results showed that an increased likelihood of koala presence in fragmented landscapes in the urban–forest interface (as opposed to larger blocks of forest habitat) can best be explained by the positive effects of soil fertility and the presence of preferred koala tree species in these fragmented areas. If koalas are to be effectively conserved in Ballarat, it is critical to (i) protect remaining core areas of high-quality habitat, including regenerating areas; (ii) protect scattered habitat patches which provide connectivity; and (iii) develop and implement habitat restoration programmes to improve habitat connectivity and enhance opportunities for safe koala movement between habitat patches intersected by main roads. [ABSTRACT FROM AUTHOR]