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Agricultural Environment (agricultural + environment)
Selected AbstractsEnterococcus faecalis with the gelatinase phenotype regulated by the fsr operon and with biofilm-forming capacity are common in the agricultural environmentENVIRONMENTAL MICROBIOLOGY, Issue 6 2009Lilia Macovei Summary The prevalence of gelatinase activity and biofilm formation among environmental enterococci was assessed. In total, 396 enterococcal isolates from swine and cattle faeces and house flies from a cattle farm were screened for gelatinase activity. The most prevalent phenotype on Todd,Hewitt agar with 1.5% skim milk was the weak protease (WP) (72.2% of isolates), followed by the strong protease (SP) 18.7%, and no protease (NP) (9.1%). The majority of WP isolates was represented by Enterococcus hirae (56.9%), followed by Enterococcus faecium (25.9%), Enterococcus casseliflavus (10.4%), Enterococcus gallinarum (5.2%) and Enterococcus saccharolyticus (1.7%). All WP isolates were negative for gelE (gelatinase) and sprE (serine protease) as well as the fsrABDC operon that regulates the two proteases, and only four isolates (7.0%) formed biofilms in vitro. All SP isolates were Enterococcus faecalis positive for the fsrABDC, gelE, sprE genes and the majority (91.2%) formed a biofilm. Diversity of NP isolates was relatively evenly distributed among E. hirae, E. faecium, E. casseliflavus, E. gallinarum, Enterococcus durans, E. saccharolyticus and Enterococcus mundtii. All NP isolates were negative for the fsr operon and only four E. hirae (11.1%) formed a biofilm. Of further interest was the loss of the gelatinase phenotype (18.9% of isolates) from SP isolates after 4 month storage at 4,8°C and several passages of subculture. Results of reverse transcription PCR analysis indicated that mRNA was produced for all the genes in the frs operon and sequencing of the gelE gene did not reveal any significant mutations. However, gelatinase was not detectable by Western blot analysis. Our study shows that E. faecalis with the complete fsr operon and the potential to form a biofilm are relatively common in the agricultural environment and may represent a source/reservoir of clinically relevant strains. In addition, many environmental enterococci, especially E. hirae, produce an unknown WP that can hydrolyse casein but does not contribute to biofilm formation. The stability of the gelatinase phenotype in E. faecalis and its regulation will require additional studies. [source] Body condition, growth rates and diet of Skylark Alauda arvensis nestlings on lowland farmlandIBIS, Issue 3 2001PAUL F. DONALD Factors affecting the diet, body condition and growth rates of Skylark chicks were assessed to examine their relationship to their agricultural environment during a critical period in the life cycle of this rapidly declining species. Rainfall explained the greatest amount of variation in body condition and growth rates and had a negative effect on both. Body condition indices were a good predictor of the likelihood of future partial brood loss to starvation. Low body condition in grass fields was related to a low diversity in the diet. Chicks fed insect larvae had higher body condition indices than those not fed larvae. Larger broods tended to have higher growth rates than smaller ones, whereas smaller broods tended to have higher body condition indices. Natural brood size reduction through the non-hatching of eggs resulted in higher body condition indices than were found in nests with the same number of chicks where all eggs hatched, this effect being independent of absolute brood size. There was no significant difference between crop types in the distance adult birds flew to forage for food for nestlings and foraging crop destination had no effect on chick development. Differences between crop types in chick diet could be related to the documented effects of pesticides on different prey species. We suggest that recent agricultural changes have affected diet and possibly body condition, but that these effects are unlikely to have been an important factor in recent population declines. [source] Ecological network analysis: an application to the evaluation of effects of pesticide use in an agricultural environmentPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 10 2007Peter Andras Abstract Ecological network analysis is used to evaluate the impact of pesticide use on ecological systems in the context of agricultural farmland environments. The aim is to provide support for the design of effective and minimally damaging pest control strategies. The ecological network analysis can identify species that are important to the integrity of the ecological network. The methodology can be used to monitor the impact of shifts in terms of types of pesticide used on the ecological system. The authors' intention is to use this methodology to provide supporting evidence for the UK Voluntary Initiative programme aimed at convincing farmers voluntarily to make improved choices in the use of a wide range of pesticides. Copyright © 2007 Society of Chemical Industry [source] The future of IPM: whither or wither?AUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 2 2009Myron P Zalucki Abstract The acronym IPM (integrated pest management) has been around for over 50 years and now not only supposedly guides research and extension in pest management but also markets pesticides, is claimed to be undertaken by many growers, and even resonates with public perceptions and politicians. Whether or not IPM programs are sustainable in the longer term under the conflicting stresses and strains of the modern agricultural environment is debatable. We analyse three case studies of IPM development in Australia: citrus IPM in central Queensland, Brassica IPM in southeast Queensland and Helicoverpa management in cotton in eastern Australia. Many management practices for these pests have changed over time. In the more stable citrus system classical biological control along with changed practices (reduced pesticide use) have effectively controlled imported scale insect pests. In Brassicas and cotton, IPM is predominantly of the sample and spray variety where, increasingly, less broad-spectrum insecticides are used and, in cotton, Helicoverpa management includes the deployment of transgenic plants. We question whether or not IPM principles are always consistent with market forces and whether or not the approach is universally applicable for all pest insects when implemented at the small (field or farm) scale. Farmers will adopt cost-effective approaches that minimise their financial risks. For Australia as a whole over the last 30 years insecticide input costs per hectare have increased faster than the price index, reflecting more costly insecticides, changes to the combinations of crops grown and an increase in the overall area of crops cultivated together with possible concomitant changes in pest abundance. Any pest crisis will ensure rapid changes in practice and adoption of technologies, in order to mitigate the short-term financial stresses caused. However, regression to former practices tends to follow (e.g. in Brassica crops). In most cases, we cannot objectively test if changed management practices are responsible for changes in pest abundance, as is often claimed, or if the latter is simply a consequence of the weather and/or related large-scale landscape features (e.g. area of host plants). We argue that for many systems the future of pest management practice will require a change to landscape or area-wide approaches. We suspect, given how entrenched the acronym has become, whatever the nature of the approach it will be called IPM. [source] Microevolution in agricultural environments: how a traditional Amerindian farming practice favours heterozygosity in cassava (Manihot esculenta Crantz, Euphorbiaceae)ECOLOGY LETTERS, Issue 2 2005Benoît Pujol Abstract We demonstrate a novel case of selection for heterozygosity in nature, involving inadvertent human selection on a population of domesticated plants. Amerindian farmers propagate cassava (Manihot esculenta) clonally by cuttings. Seedlings also appear spontaneously in fields, and farmers allow them to grow, later using some for cuttings. These ,volunteers' contribute new genotypes. However, many are inbred, whereas multiplied clones are highly heterozygous. We demonstrate the selective retention of heterozygous volunteers. When farmers weeded fields, they killed small volunteers, but retained large ones. Plant size and heterozygosity were correlated, and both increased after weeding. The process we document allows maintenance of genotypically diverse and heterozygous clonal stocks. Demonstrating heterosis in nature usually requires large sample sizes, but novel features of our system allowed escape of this constraint. Traditional agroecosystems offer unusual opportunities for the microevolutionary studies required to give on-farm conservation of genetic resources a solid scientific basis. [source] Operational performance of current synthetic aperture radar sensors in mapping soil surface characteristics in agricultural environments: application to hydrological and erosion modellingHYDROLOGICAL PROCESSES, Issue 1 2008Nicolas Baghdadi Abstract Synthetic aperture radar (SAR) sensors are often used to characterize the surface of bare soils in agricultural environments. They enable the soil moisture and roughness to be estimated with constraints linked to the configurations of the sensors (polarization, incidence angle and radar wavelength). These key soil characteristics are necessary for different applications, such as hydrology and risk prediction. This article reviews the potential of currently operational SAR sensors and those planned for the near future to characterize soil surface as a function of users' needs. It details what it is possible to achieve in terms of mapping soil moisture and roughness by specifying optimal radar configurations and the precision associated with the estimation of soil surface characteristics. The summary carried out for the present article shows that mapping soil moisture is optimal with SAR sensors at low incidence angles (<35 ). This configuration, which enables an estimated moisture accuracy greater than 6% is possible several times a month taking into account all the current and future sensors. Concerning soil roughness, it is best mapped using three classes (smooth, moderately rough, and rough). Such mapping requires high-incidence data, which is possible with certain current sensors (RADARSAT-1 and ASAR both in band C). When L-band sensors (ALOS) become available, this mapping accuracy should improve because the sensitivity of the radar signal to Soil Surface Characteristics (SSC) increases with wavelength. Finally, the polarimetric mode of certain imminent sensors (ALOS, RADARSAT-2, TerraSAR-X, etc.), and the possibility of acquiring data at very high spatial resolution (metre scale), offer great potential in terms of improving the quality of SSC mapping. Copyright © 2007 John Wiley & Sons, Ltd. [source] Nitrogen fertilisation in coriander (Coriandrum sativum L.): a review and meta-analysisJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 6 2009Alessandra Carrubba Abstract Nitrogen (N) fertilisation is one of the most important external inputs in assessing coriander seed yield and plant growth. Recent concerns related to the misuse of N fertilisers in agricultural environments, however, stress the opportunity for a fine-tuning of N management in order to optimise the use of this element, avoiding losses and reducing environmental hazards. In this study, some results from the literature concerning N fertilisation in coriander are reviewed and, by means of statistical analysis, an attempt is made to derive from them some general suggestions about practices of N fertilisation. In most cases examined, N fertilisation allowed a 10,70% increase in seed yields in comparison with each respective untreated control. The efficiency of use of this element, however, has proven to be greatly dependent on the overall fertility conditions of the growing site. The greatest yield advantages were actually found in more favourable environments, whereas in low-yielding environments plants reached their maximum yield with a comparatively reduced N supply. In low-yielding environments a careful risk/benefit assessment of this practice is therefore advisable. No definite conclusion could be drawn at this stage about essential oil yield and composition in relation to N fertilisation. Copyright © 2009 Society of Chemical Industry [source] Invasive ants in Australia: documented and potential ecological consequencesAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 4 2008Lori Lach Abstract A growing number of species are being transported and introduced by humans to new locations and are establishing self-sustaining populations outside their native ranges. Since ants play many ecological roles, introduction of an invasive ant species, and subsequent disruption of Australia's rich and abundant native ant fauna, has the potential for numerous adverse consequences. Over 6700 ants representing 105 species from 73 genera have been intercepted at Australian ports of entry in the last 20 years and all six of the world's most destructive invasive ants have become established in the country. Here we review the current and potential consequences of these ants on Australia's natural and agricultural environments. To date, several studies, most involving the big-headed ant, Pheidole megacephala, and the Argentine ant, Linepithema humile, have documented a decline in native ant species richness. The displacement of native ants by these invaders could have multiple consequences for the native flora and fauna. Since few of these have been investigated in Australia, we combine knowledge from invasions elsewhere, the ecology of the interactions, and data on current and predicted geographic ranges of introduced ants to hypothesise about likely indirect effects of invasive ants in Australia. Further investigations that are aimed at testing these predictions will also aid in justifying and prioritising national prevention and control efforts, and will contribute to some of the long-standing questions about ant invasions globally. [source] | |||||||||||||