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Recoupling C and N cycles: a fertiliser template to synchronise N supply and limit C priming?
No full textDespite their advantages in plant productivity, plant uptake from conventional nitrogen (N) fertilisers is around 50%. To test whether recoupling carbon (C) and N cycles can decrease losses and increase N use efficiency (NUE), four experiments were conducted. Two growth accelerator pot experiments in contrasting soils were conducted with N additions representing a range of molar C to N ratios (Cmol:Nmol; 0.5 to 11) formulated from urea (U) and waste-derived materials (sugarcane trash, Ct; pelletised beef manure, B; dairy digestate, D; insect larvae, L; protein meal from insect larvae, P; and anaerobic pond sludge, S) with and without a nitrification inhibitor (I). Two reaction vessel experiments were conducted for measuring N-transformation based on continuous on-line nitrous oxide (N2O) and carbon dioxide (CO2) monitoring, and soil analyses. Adverse impacts of these stoichiometric formulations on C priming were examined using natural abundance isotopic signatures. Relative to urea, higher N use efficiency (∼2 to 3 times) was achieved with waste derived (i.e., D, S, B, and P) formulations with I, with and without C. Increased Cmol:Nmol ratio increased post-experiment N retention in the fertiliser layer and delayed N uptake by the plant. Carbon priming losses were least with formulation Cmol:Nmol from 3.1 to 6.2. Our results suggest waste-derived stoichiometrically tailored formulations with an inhibitor have potential to avoid soil C priming, deliver better NUE, decrease N leaching losses, and increase N stocks in the soil profile
Spatial probabilistic patterns of joint heat and water stress of chickpea in Australia
No full textQuantitative characterisation of the crop environment for breeding and agronomic applications is commonly based on the cluster analysis of isolated climate factors, such as drought and temperature. The focus on individual climate factors fails to account for both the correlations between climate factors in space and time, and the contemporary models of dynamic biological systems where multiple interacting factors simultaneously shape the crop phenotype. With a focus on chickpea in Australia, our aims are to (1) assess the associations between climate factors and actual yield measured in 578 location -years; associations are investigated on a biologically relevant developmental scale; (2) establish the spatial, probabilistic patterns of multivariate environment types at regional and continental scales; and (3) evaluate the shifts in the frequency of environment types with climate change.
We identified a syndrome of hot, dry and high vapour pressure deficit with three intensities of stress classified as low, medium and high. Measured yield, in the range from failed crop to 4 t ha -1 , aligned more strongly with this multivariate syndrome than with isolated climate factors, with stronger associations at regional than continental scale. The frequency of stressful environment types increased with realised climate change and was most severe in the chickpea growing heartland of central Queensland; our models show that increased frequency of stress could be partially mitigated with earlier flowering varieties. Our findings will inform chickpea agronomy, phenotyping and breeding
Root decomposition in coastal wetlands of Southeast Queensland, Australia
No full textRoot decomposition is a key coastal wetland ecological process. Despite this, there are limited empirical studies on root decomposition. In this study, we investigated the effect of species, root size and burial habitat on root decomposition of supratidal tree species (Casuarina glauca, Melaleuca quinquenervia), and intertidal mangrove (Avicennia marina) and saltmarsh species (Sarcocornia quinqueflora, Sporobolus virginicus) in Southeast Queensland, Australia. Decomposition curves for all tested factors indicated a plateau in remaining root mass by the end of the experiment; the plateau was therefore inferred to indicate the “expected liable fraction”. Root decomposition rates and fractions of expected labile root biomass of supratidal and intertidal species were not significantly different. The percentage mass remaining of fine roots (<2 mm) of woody species varied by species, but that of coarse roots (2–20 mm) did not vary among species. Decomposition rates and expected labile fractions of roots of intertidal species were not significantly different between burial in the same habitat (“at home”) versus in habitats dominated by other species (“away”). Overall, we found lowest variation in percentage mass remaining, followed by expected labile fractions and root decomposition rates across species and habitats after 14 months. The mean root decomposition rate using two-pool asymptotic models was 0.0169 ± 0.0019 day−1; the mean expected labile fraction was 28.3 ± 1.0 %. These experimental root decomposition results across the intertidal to supratidal zone provide insights to the drivers of decomposition rates in coastal wetlands that can be used in ecological models
Susceptibility to cyantraniliprole in Australian Spodoptera frugiperda (Lepidoptera Noctuidae) and establishment of diagnostic tests for resistance management
No full textDiamides are an important class of insecticides for control of insect pests in Australian farming systems. Their favourable toxicological and environmental profiles have led to broad registration across multiple pest species and crop types. However, widespread use is known to compromise insecticidal efficacy due to resistance, and concerns have been raised about the sustainability of these insecticides in Australian agriculture, particularly since the incursion of Spodoptera frugiperda in 2020. As a first step in pre‐emptive management of S. frugiperda , baseline susceptibility to cyantraniliprole was determined in larval bioassays performed on 16 field populations collected from maize and sweet corn between 2020 and 2021 during the initial period of establishment in Australia. There was a narrow (2.1‐fold) range of intra‐specific variation in cyantraniliprole susceptibility amongst field populations. The average median lethal concentration was 0.088 mg L −1 , which was significantly higher than in Helicoverpa armigera (LC 50 = 0.037 mg L −1 ). An analysis of relative diamide toxicity showed that while the median concentration of chlorantraniliprole was significantly higher than cyantraniliprole in S. frugiperda , there was no significant difference between the toxicity of chlorantraniliprole and cyantraniliprole at the LC 99.9 level. Using the dose–response data generated from these bioassays and taking into account empirical survival, a concentration of 2 mg L −1 of cyantraniliprole was determined to be a suitable dose for discriminating between cyantraniliprole‐susceptible and cyantraniliprole‐insensitive phenotypes of S. frugiperda
Alternaria and Stemphylium species associated with leaf blight and fruit rot of field-grown tomatoes in Australia
No full textField-grown tomatoes with fruit rot and leaf early blight symptoms were sampled from New South Wales and Victoria, Australia, in 2022 and 2023. Alternaria alternata, A. arborescens, A. fructicola, and Stemphylium eturmiunum were isolated from black, sunken lesions on the fruit. Alternaria alternata, A. lycopersicifolia and an unidentified Alternaria sp. were isolated from leaf lesions. Alternaria alternata, A. arborescens and S. eturmiunum are known to cause foliar and postharvest diseases of tomato, globally. The pathogenicity of A. lycopersicifolia and A. fructicola on tomato leaves and fruits was confirmed by Koch’s postulates. Higher than expected species diversity was detected among fungal species associated with symptomatic tomato leaves and fruits. This is the first report of S. eturmiunum on tomato in Australia. The prevalence of these species and the potential risks posed by mycotoxin contamination are needed to assess their impact on the tomato industry
Diversification of an emerging bacterial plant pathogen; insights into the global spread of Xanthomonas euvesicatoria pv. perforans
No full textBacterial diseases pose significant threats to food security by reducing crop yield and increasing production costs. Managing these diseases is particularly challenging when pathogen populations are genetically diverse, rapidly evolving, and capable of long-distance dispersal. Xanthomonas euvesicatoria pv. perforans (Xep), one of the pathogens responsible for bacterial spot disease of tomato, exemplifies these challenges. Since its discovery in Florida in 1991, Xep has spread globally, affecting tomatoes in warm and wet production regions worldwide. Previous studies have indicated genetic diversity within Xep, suggesting the emergence of multiple lineages, but there was not a comprehensive global analysis. Here, we examined genome sequences of Xep strains from five continents and discovered extensive genetic diversity, including in genes important for virulence and breeding for resistance in tomatoes. In addition, we found that genetically similar strains were present on different continents, likely due to the international movement of contaminated seeds through global production chains. Our findings underscore the need for periodic monitoring of these pathogen populations and new approaches to effectively manage bacterial spot disease of tomato
Land-use effects on aphid-parasitoid-hyperparasitoid food web structure and function
No full textUnderstanding the impact of land-use intensity on aphid-parasitoid food web structure and biological control services is crucial for managing landscapes in a way that supports natural pest regulation. However, few studies have directly linked the structure of these food webs to actual pest control outcomes. In this study, we analyzed how the structure of aphid-parasitoid food webs and the ecosystem services they provide varied across a land-use intensity gradient in 24 alfalfa fields during three years in China. Beta diversity result indicates that the regional species pools play a key role in local food web assembly. Species in plain regions (intensive agricultural areas) were subsets of those found in mountainous region (more diverse landscapes), indicating that land-use intensity filtered out species from the broader regional pool rather than creating unique local assemblages. Land-use intensity, particularly mowing and insecticide application, negatively impacted both primary parasitoid and hyperparasitoid richness and abundance. Conversely, noncrop areas positively influenced primary parasitoid richness. Food web structures varied across regions and sampling dates. Hyperparasitism was significantly correlated with food web structural metrics, showing a negative relationship with modularity and a positive relationship with nestedness in primary-hyperparasitoid food webs. It suggests that hyperparasitoids may be more effective in suppressing primary parasitoids and thereby aphid biocontrol in less modular and more interconnected food webs. These findings highlight the importance of food web structure in shaping parasitoid dynamics and emphasize the need for landscape management strategies that promote biodiversity and ecosystem functions
Pig carcass decomposition dynamics: Insights into carcass disposal for emergency animal disease management
No full textAustralia is free from many economically devastating emergency animal diseases (EADs) that threaten livestock production in neighbouring countries. In Australia, an important consideration for EAD control is managing susceptible feral animal populations, especially in remote and inaccessible areas where carcass disposal poses considerable logistical challenges. One proposed solution is to utilise natural decomposition above ground through the ‘destroy and let lie’ (D&LL) method, relying on post-mortem changes in carcass temperature and pH to inactivate the EAD agent. We investigated temperature and pH changes in pig carcasses from death until end-stage decomposition at two locations in Queensland to gain insights into how carcasses left in situ decompose under Australian conditions. Using regression modelling, we identified days since humane killing, air temperature, rainfall, relative humidity, anatomical site and study location as significant predictors of carcass pH and temperature. Although the observed carcass pH and temperature conditions did not meet African swine fever virus (ASFV) inactivation thresholds, foot-and-mouth disease virus (FMDV) was likely to be inactivated in the thoracic cavity, superficial and deep skeletal muscle and abdominal cavity of most carcasses. However, FMDV inactivation thresholds were not reached in bone marrow and brain. This suggests that these carcasses may potentially remain infectious with ASFV and FMDV in situ under the experimental conditions encountered, based on the inactivation thresholds selected. Despite this, culling large portions of a feral pig population, in conjunction with D&LL disposal approach, may still support disease control imperatives during an EAD response by reducing live pig numbers and disease transmission
Quantifying feral pig interactions to inform disease transmission networks
No full textFeral pigs threaten biodiversity in 54 countries and cause an estimated $120 billion in damages annually in the USA. They endanger over 600 native species and have driven 14 to extinction. Additionally, they pose a significant zoonotic disease risk, carrying pathogens such as Brucella, leptospirosis, and Japanese encephalitis. Understanding and controlling disease spread relies on models of social dynamics, but these vary widely across regions, limiting the transferability of findings from the USA and Europe to other locations like Australia. This study addresses this gap by analysing the social interactions of 146 GPS-tracked feral pigs in Australia using a proximity-based social network approach. Findings reveal that females exhibit stronger group cohesion, while males act as key connectors between groups. Contact rates are high within groups, facilitating rapid intra-group disease spread, whereas inter-group transmission is slower. Seasonal variations further impact dynamics, with increased contact in summer. These insights suggest that targeting adult males in control programs could help limit disease outbreaks. Given the rising economic and public health concerns associated with animal diseases, the study highlights the need for localized strategies based on feral pig social behaviour to enhance global control efforts
Deviation From the Regression of Yield on Nitrogen Fertiliser Rate as a Tool for Detecting Fraud in Organic Banana Production
No full textBackground and aims Bananas are demanding in nitrogen (N) input; therefore, there is a temptation for organic farmers for using synthetic N fertilisers, which are not allowed under organic standards. The aim of our study was to develop a tool that identifies high banana yields obtained with suspiciously low organic N input. Methods We systematically reviewed literature from experimental studies on N fertilisation in bananas from all over the world. We also developed a simplified N balance model for organic bananas. Furthermore, N fertilisation and banana yield data from organic and conventional farmers in different countries were collected. From these, a subset of trustworthy organic farms was identified, as a reference concerning plausible ratios of yield versus fertilisation. A model was developed to estimate the deviation from the regression of trustworthy farms and thus identify suspicious cases. Results Neither literature nor the N balance led to a meaningful benchmark for differentiating plausible from non-plausible yields. The regression of yield on N fertiliser rate from the trustworthy organic farmers, however, turned out to be a helpful reference, and the deviation from this regression helps to achieve our aim. Depending on the alert limit, that is, the probability of obtaining false positive results, 4, 6, or 9 out of 157 data-pairs from organic farmers turned out to be suspicious. Conclusion Measuring deviation from the regression of the trustworthy farms is a useful tool for identifying organic banana farmers suspected to be using synthetic N fertilisers but is not in itself a proof of fraud. The model will improve as more data becomes available