Reilly K.,Teagasc |
Cullen E.,Teagasc |
Cullen E.,University of Wisconsin - Madison |
Lola-Luz T.,Teagasc |
And 8 more authors.
Journal of the Science of Food and Agriculture | Year: 2013
BACKGROUND: Responses of the soil microbial and nematode community to organic and conventional agricultural practices were studied using the Teagasc Kinsealy Systems Comparison trial as the experimental system. The trial is a long-term field experiment which divides conventional and organic agriculture into component pest-control and soil treatment practices. We hypothesised that management practices would affect soil ecology and used community level physiological profiles, microbial and nematode counts, and denaturing gradient gel electrophoresis (DGGE) to characterise soil microbial communities in plots used for onion (Allium cepa L.) cultivation. RESULTS: Microbial activity and culturable bacterial counts were significantly higher under fully organic management. Culturable fungi, actinomycete and nematode counts showed a consistent trend towards higher numbers under fully organic management but these data were not statistically significant. No differences were found in the fungal/bacterial ratio. DGGE banding patterns and sequencing of excised bands showed clear differences between treatments. Putative onion fungal pathogens were predominantly sequenced under conventional soil treatment practices whilst putative soil suppressive bacterial species were predominantly sequenced from the organic pest-control treatment plots. CONCLUSION: Organic management increased microbial activity and diversity. Sequence data was indicative of differences in functional groups and warrants further investigation. © 2013 Society of Chemical Industry.
Johnson S.N.,University of Western Sydney |
Benefer C.M.,University of Plymouth |
Frew A.,University of Western Sydney |
Griffiths B.S.,SRUC Crop and Soil Systems Research Group |
And 6 more authors.
Applied Soil Ecology | Year: 2016
Herbivorous insect pests living in the soil represent a significant challenge to food security given their persistence, the acute damage they cause to plants and the difficulties associated with managing their populations. Ecological research effort into rhizosphere interactions has increased dramatically in the last decade and we are beginning to understand, in particular, the ecology of how plants defend themselves against soil-dwelling pests. In this review, we synthesise information about four key ecological mechanisms occurring in the rhizosphere or surrounding soil that confer plant protection against root herbivores. We focus on root tolerance, root resistance via direct physical and chemical defences, particularly via acquisition of silicon-based plant defences, integration of plant mutualists (microbes and entomopathogenic nematodes, EPNs) and the influence of soil history and feedbacks. Their suitability as management tools, current limitations for their application, and the opportunities for development are evaluated. We identify opportunities for synergy between these aspects of rhizosphere ecology, such as mycorrhizal fungi negatively affecting pests at the root-interface but also increasing plant uptake of silicon, which is also known to reduce herbivory. Finally, we set out research priorities for developing potential novel management strategies. © 2016 Elsevier B.V.
Ball B.C.,SRUC Crop and Soil Systems Research Group
European Journal of Soil Science | Year: 2013
Soil structure affects microbial activity and thus influences greenhouse gas production and exchange in soil. Structure is variable and increasingly vulnerable to compaction and erosion damage as agriculture intensifies and climate changes. Few studies have specifically related the impact of structure and its variability to greenhouse gas (GHG) emissions over a wide range of soils and management treatments. The objective of this study was to draw from research in Scotland, Japan and New Zealand, which examined how soil structures affected by wheel compaction, animal trampling, tillage and land-use change influence GHG emissions in order to help identify key controlling properties. Nitrous oxide (N2O) is the main focus, though carbon dioxide (CO2), methane (CH4) and nitric oxide (NO) are included. Gas emissions were measured by using static chambers in the field or incubated intact cores. Poor structure, measured as small relative gas diffusivities and air permeabilities, restricted aeration, resulting in N2O emission or consumption dependent on mineral nitrogen contents. Structural damage (identifiable using the Visual Evaluation of Soil Structure) was especially important near the soil surface where microsites of microbial activity were exposed and aeration was impaired. Moist, well-aerated soils favoured CH4 oxidation and CO2 exchange. N2O emissions were not necessarily increased in anaerobic soils because of possible N2O consumption and microbial adaptation. Soil matric potential, volumetric water content, relative diffusivity, air permeability and water-filled pore space are relevant indicators for N2O and CH4 flux and aeration status. As pore continuity and size are so relevant, pore-scale models are likely to have an increasing role in understanding mechanisms of GHG production, transport and release. © 2013 The Author. Journal compilation © 2013 British Society of Soil Science.