Effect of added nitrogen on plant litter decomposition depends on initial soil carbon and nitrogen stoichiometry

Increasing organic carbon inputs to agricultural soils through the use of pastures or crop residues has been suggested as a means of restoring soil organic carbon lost via anthropogenic activities, such as land use change. However, the decomposition and retention of different plant residues in soil, and how these processes are affected by soil properties and nitrogen fertiliser application, is not fully understood. We evaluated the rate and extent of decomposition of 13C-pulse labelled plant material in response to nitrogen addition in four pasture soils of varying physico-chemical characteristics. Microbial respiration of buffel grass (Cenchrus ciliaris L.), wheat (Triticum aestivum L.) and lucerne (Medicago sativa L.) residues was monitored over 365-days. A double exponential model fitted to the data suggested that microbial respiration occurred as an early rapid and a late slow stage. A weighted three-compartment mixing model estimated the decomposition of both soluble and insoluble plant 13C (mg C kg−1 soil). Total plant material decomposition followed the alkyl C: O-alkyl C ratio of plant material, as determined by solid-state 13C nuclear magnetic resonance spectroscopy. Urea-N addition increased the decomposition of insoluble plant 13C in some soils (≤0.1% total nitrogen) but not others (0.3% total nitrogen). Principal components regression analysis indicated that 26% of the variability of plant material decomposition was explained by soil physico-chemical characteristics (P = 0.001), which was primarily described by the C:N ratio. We conclude that plant species with increasing alkyl C: O-alkyl C ratio are better retained as soil organic matter, and that the C:N stoichiometry of soils determines whether N addition leads to increases in soil organic carbon stocks.

A Genetic Analysis of Lysosomal Enzyme Activities in Brahman Cattle

Analyses of variance and co variance were carried out on the activities of three lysosomal enzymes in mononuclear blood cells from Brahman cattle. These were hexosaminidase (HEX), beta-D-galacto-sidase (GAL) and acid alpha-glucosidase (GLU) which had been measured in blood mononuclear cells from 1752 cattle from 6 herds in a Pompe's disease control programme. Herd of origin and date of bleeding significantly affected the level of activity of all enzymes. In addition, HEX and GAL were affected by age and HEX by the sex of the animal bled. Estimates of heritability from sire variances were 0.29:t 0.09 for HEX, 0.31 :t 0.09 for GAL and 0.44:t 0.09 for GLU. Genetic correlations between all enzymes were positive. The data indicate the existence of a major gene causing Pompe's disease and responsible for 16% of the genetic variation in GLU. One standard deviation of selection differential for high GLU should almost eliminate Pompe's disease from the population. The effi-ciency of selection would be aided by estimating the breeding value for GLU using measurements of HEX and GLU and taking account of an animal's sex, age, date of bleeding and herd of origin.

Summative evaluation of climate application activities with pastoralists in western Queensland

Survey methods were engaged to measure the change in use and knowledge of climate information by pastoralists in western Queensland. The initial mail survey was undertaken in 2000-01 (n=43) and provided a useful benchmark of pastoralists climate knowledge. Two years of climate applications activities were completed and clients were re-surveyed in 2003 (n=49) to measure the change in knowledge and assess the effectiveness of the climate applications activities. Two methods were used to assess changes in client knowledge, viz., self-assessment and test questions. We found that the use of seasonal climate forecasts in decision making increased from 36% in 2001 (n=42) to 51% in 2003 (n=49) (P=0.07). The self-assessment technique was unsatisfactory as a measure of changing knowledge over short periods (1-3 years), but the test question technique was successful and indicated an improvement in climate knowledge among respondents. The increased levels of use of seasonal climate forecasts in management and improved knowledge was partly attributed to the climate applications activities of the project. Further, those who used seasonal forecasting (n=25) didn't understand key components of forecasts (e.g. probability, median) better than those who didn't use seasonal forecasts (n=24) (P>0.05). This identifies the potential for misunderstanding and misinterpretation of forecasts among users and highlights the need for providers of forecasts to understand the difficulties and prepare simply written descriptions of forecasts and disseminate these with the maps showing probabilities. The most preferred means of accessing climate information were internet, email, 'The Season Ahead' newsletter and newspaper. The least preferred were direct contact with extension officers and attending field days and group meetings. Eighty-six percent of respondents used the internet and 67% used ADSL broadband internet (April 2003). Despite these findings, extension officers play a key role in preparing and publishing the information on the web, in emails and newsletters. We also believe that direct contact with extension officers trained in climate applications is desirable in workshop-like events to improve knowledge of the difficult concepts underpinning climate forecasts, which may then stimulate further adoption.

Analysing industry needs to fine tune IPM project activities

As a first step to better targeting the activities of a project for improving management of western flower thrips, Frankliniella occidentialis, (WFT) in field grown vegetable crops, we surveyed growers, consultants and other agribusiness personnel in two regions of Queensland. Using face-to-face interviews, we collected data on key pests and measures used to manage them, the importance of WFT and associated viral diseases, sources of pest management information and additional skills and knowledge needed by growers and industry. Responses were similar in the two regions. While capsicum growers in one northern Queensland district had suffered serious losses from WFT damage in 2002, in general the pest was not seen as a major problem. In cucurbit crops, the silverleaf whitefly (Bemisia tabaci biotype B) was considered the most difficult insect pest to manage. Pest control tactics were largely based on pesticides although many respondents mentioned non-chemical methods such as good farm hygiene practices, control of weed hosts and regular crop monitoring, particularly when prompted. Respondents wanted to know more about pest identification, biology and damage, spray application and the best use of insecticides. Natural enemies were mentioned infrequently. Keeping up to date with available pesticide options, availability of new chemicals and options for a district-wide approach to managing pests emerged as key issues. Growers identified agricultural distributors, consultants, Queensland Department of Primary Industries staff, other growers and their own experience as important sources of information. Field days, workshops and seminars did not rank highly. Busy vegetable growers wanted these activities to be short and relevant, and preferred to be contacted by post and facsimile rather than email. In response to these results, we are focusing on three core, interrelated project extension strategies: (i) short workshops, seminars and farm walks to provide opportunities for discussion, training and information sharing with growers and their agribusiness advisors; (ii) communication via newsletters and information leaflets; (iii) support for commercialisation of services.

Weed spread prevention: simple activities for field operations.

This paper discusses how spread of weeds can be minimised by improved knowledge of the weed’s ecology and dispersal, and by better surveillance and treatment methods. Undertaking simple prevention activities reduces the risk of spreading weeds with minimal costs to projects and they noted that field staff and researchers can inadvertently become vectors of weed spread if they do not take adequate precautions. The authors describe several techniques that can be adopted and reference their observations to the eradication program for Siam weed, Chromolaena odorata.

A strategic approach to mitigating the impacts of wild canids: proposed activities of the Invasive Animals Cooperative Research Centre

Wild canids (wild dogs and European red foxes) cause substantial losses to Australian livestock industries and environmental values. Both species are actively managed as pests to livestock production. Contemporaneously, the dingo proportion of the wild dog population, being considered native, is protected in areas designated for wildlife conservation. Wild dogs particularly affect sheep and goat production because of the behavioural responses of domestic sheep and goats to attack, and the flexible hunting tactics of wild dogs. Predation of calves, although less common, is now more economically important because of recent changes in commodity prices. Although sometimes affecting lambing and kidding rates, foxes cause fewer problems to livestock producers but have substantial impacts on environmental values, affecting the survival of small to medium-sized native fauna and affecting plant biodiversity by spreading weeds. Canid management in Australia relies heavily on the use of compound 1080-poisoned baits that can be applied aerially or by ground. Exclusion fencing, trapping, shooting, livestock-guarding animals and predator calling with shooting are also used. The new Invasive Animals Cooperative Research Centre has 40 partners representing private and public land managers, universities, and training, research and development organisations. One of the major objectives of the new IACRC is to apply a strategic approach in order to reduce the impacts of wild canids on agricultural and environmental values in Australia by 10%. In this paper, the impacts, ecology and management of wild canids in Australia are briefly reviewed and the first cooperative projects that will address IACRC objectives for improving wild dog management are outlined.

Determining and quantifying components of an aquaculture soundscape.

Recirculating aquaculture systems have a unique anthropogenic-based soundscape which is characterized by the type of equipment utilized, the structural configuration of walls, tanks, equipment, the substrate the tanks are situated on and even the activities of the personnel operating the facility. The soundscape of recirculation facilities is inadequately understood and remains poorly characterized, although it is generally accepted that the dominant sounds found in such facilities are within the hearing range of fish. The objective of this study was to evaluate the soundscape in a recirculating aquaculture facility from an intra-tank perspective and determine how the soundscape is shaped by a range of characteristics within the facility. Sounds were recorded across an operating aquaculture facility including different tank designs. The sounds recorded fell within previously measured pressure level ranges for recirculating systems, with the highest maximum sound pressure level (SPL) recorded at 124 dB re 1 mu Pa-2/Hz (with an FFT bin width of 46.9 Hz, centered at 187.5 Hz). The soundscape within the tanks was stratified and positively correlated with depth, the highest sound pressure occurring at the base of the tanks. Each recording of the soundscape was dominated by a frequency component of 187.5 Hz (corresponding centre of the 4th 46.9 Hz FFT analysis bin) that produced the highest observed SPL Analysis of sound recordings revealed that this peak SPL was associated with the acoustic signature of the pump. The soundscape was also evaluated for impacts of tank hood position, time of day, transient sounds and airstone particle size types, all of which were found to appreciably influence sound levels and structure within the tank environment. This study further discusses the distinctiveness of the soundscape, how it is shaped by the various operating components and considers the aquaculture soundscape in relation to natural soundscapes found within aquatic tropical environments.

A review of Australian classical biological control of weeds programs and research activities over the past 12 years

Considerable progress has been made towards the successful classical biological control of many of Australia’s exotic weeds over the past decade. Some 43 new arthropod or pathogen agents were released in 19 projects. Effective biological control was achieved in several projects with the outstanding successes being the control of rubber vine, Cryptostegia grandiflora, and bridal creeper, Asparagus asparagoides. Significant developments also occurred in target prioritization, procedures for target and agent approval, funding, infrastructure and cooperation between agencies. Scientific developments included greater emphasis on climate matching, plant and agent phylogeny, molecular diagnostics, agent prioritization and agent evaluation.

Transition of EGA wheat breeding activities to Australian Grain Technologies

Transition of EGA wheat breeding activities to Australian Grain Technologies.

Biology, ecology and conservation of the Mobulidae

The Mobulidae are zooplanktivorous elasmobranchs comprising two recognized species of manta rays (Manta spp.) and nine recognized species of devil rays (Mobula spp.). They are found circumglobally in tropical, subtropical and temperate coastal waters. Although mobulids have been recorded for over 400 years, critical knowledge gaps still compromise the ability to assess the status of these species. On the basis of a review of 263 publications, a comparative synthesis of the biology and ecology of mobulids was conducted to examine their evolution, taxonomy, distribution, population trends, movements and aggregation, reproduction, growth and longevity, feeding, natural mortality and direct and indirect anthropogenic threats. There has been a marked increase in the number of published studies on mobulids since c. 1990, particularly for the genus Manta, although the genus Mobula remains poorly understood. Mobulid species have many common biological characteristics although their ecologies appear to be species-specific, and sometimes region-specific. Movement studies suggest that mobulids are highly mobile and have the potential to rapidly travel large distances. Fishing pressure is the major threat to many mobulid populations, with current levels of exploitation in target fisheries unlikely to be sustainable. Advances in the fields of population genetics, acoustic and satellite tracking, and stable-isotope and fatty-acid analyses will provide new insights into the biology and ecology of these species. Future research should focus on the uncertain taxonomy of mobulid species, the degree of overlap between their large-scale movement and human activities such as fisheries and pollution, and the need for management of inter-jurisdictional fisheries in developing nations to ensure their long-term sustainability. Closer collaboration among researchers worldwide is necessary to ensure standardized sampling and modelling methodologies to underpin global population estimates and status.

Efficacy of acibenzolar-S-methyl (Bion®) treatment of Australian commercial passionfruit, Passiflora edulis f. sp. flavicarpa, on resistance to Passionfruit woodiness virus (PWV) and activities of chitinase & β-1,3-glucanase

This greenhouse study investigated the efficacy of acibenzolar-S-methyl (Bion®) treatment of lower leaves of passionfruit, (Passiflora edulis f. sp. flavicarpa), on Passionfruit woodiness disease and activities of two pathogenesis-related proteins, chitinase and β-1,3-glucanase after inoculation with passionfruit woodiness virus (PWV). All Bion® concentrations reduced disease symptoms, but the concentration of 0.025 g active ingredient (a.i.)/l was the most effective, reducing disease severity in systemic leaves by 23, 29 and 30 compared with water-treated controls at 30, 40 and 50 days post inoculation (dpi) with PWV, respectively. Correspondingly, relative virus concentration as determined by DAS-ELISA in the upper, untreated leaves (new growth) above the site of inoculation at 50 dpi was reduced by 17 and 22 in plants treated with 0.025 and 0.05 g a.i./l, respectively. Bion® treatment and subsequent inoculation with PWV increased chitinase and β-1,3-glucanase activities in the new leaves above the site of inoculation at 30 dpi with PWV. It was concluded that optimal protective Bion® treatment concentrations were 0.025 and 0.05 g a.i./l.