Elizabeth A. Stockdale
Rothamsted Research
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Featured researches published by Elizabeth A. Stockdale.
Advances in Agronomy | 2003
Daniel Murphy; Sylvie Recous; Elizabeth A. Stockdale; I. R. P. Fillery; Lars Stoumann Jensen; D. J. Hatch; K. W. T. Goulding
Abstract Isotopic pool dilution using 15 N is proving to be a valuable tool for increasing our understanding of gross N cycling processes and our ability to both model these processes and link them to microbial function. However, not all applications are appropriate. Many of the questions asked by agronomists and soil scientists can often be addressed by simpler experiments in which measurements of the main parameters of inorganic and total N content of soil and plant components would suffice. In addition, the theory, assumptions and techniques associated with the calculation of gross N fluxes can lead to large errors if not applied correctly. Some preliminary assessment of the principle N transformation processes to be studied, followed by an optimisation of the experimental conditions are needed for the effective application of 15 N pool dilution. When applied correctly under carefully controlled laboratory incubations, the technique has been used successfully to quantify gross N fluxes and to understand the fundamental processes that regulate individual microbial N pathways. This has improved our understanding of how C and N cycles are linked, and thus has led us to question the most appropriate structure of C and N cycling models. Field based 15 N pool dilution studies have been used successfully to study the climatic influence on the soil N cycle and also to quantify the impact of external inputs. Further field-based studies are required to aid model development and evaluation. Linking soil microbial/molecular ecology with process-based studies of microbial nutrient cycling presents a new and exciting field of research that will benefit from the further application of isotopic pool dilution techniques for N and other nutrients.
Soil Research | 2006
William Cookson; Petra Marschner; Ian Clark; N. Milton; Michael Smirk; Daniel V. Murphy; M. Osman; Elizabeth A. Stockdale; Penny R. Hirsch
The aim of this study was to assess the influence of season, farm management (organic, biodynamic, integrated, and conventional), and soil chemical, physical, and biological properties on gross nitrogen (N) fluxes and bacterial community structure in the semi-arid region of Western Australia. Moisture availability was the dominant factor mediating microbial activity and carbon (C) and N cycling under this climate. In general, microbial biomass N, dissolved organic N, and potentially mineralisable N were greater in organic and biodynamic than integrated and conventional soil. Our results indicate that greater silt and clay content in organic and biodynamic soil may also partly explain these differences in soil N pools, rather than management alone. Although plant-available N (NH4+ + NO3–) was greater in conventional soil, this was largely the result of higher NO3– production. Multiple linear modelling indicated that soil temperature, moisture, soil textural classes, pH, electrical conductivity (EC), and C and N pools were important in predicting gross N fluxes. Redundancy analysis revealed that bacterial community structure, assessed by denaturing gradient gel electrophoresis of 16S rDNA, was correlated with C and N pools and fluxes, confirming links between bacterial structure and function. Bacterial community structure was also correlated with soil textural classes and soil temperature but not soil moisture. These results indicate that across this semi-arid landscape, soil bacterial communities are relatively resistant to water stress.
Kluwer Academic Publishers | 2007
Daniel V. Murphy; Elizabeth A. Stockdale; P.C. Brookes; K. W. T. Goulding
Microorganisms (e.g. bacteria, fungi, actinomycetes, microalgae) play a key role in organic matter decomposition, nutrient cycling and other chemical transformations in soil. In fact general measurements of microbial activity in soil are synonymous with the breakdown of organic matter. Decomposition of organic matter is usually controlled by heterotrophic microorganisms and leads to the release and cycling of nutrients (especially nitrogen (N), sulphur (S) and phosphorus (P)). Microorganisms also immobilise significant amounts of carbon (C) and other nutrients within their cells. The total mass of living microorganisms (the microbial biomass) therefore has a central role as source, sink and regulator of the transformations of energy and nutrients in soil (Table 1). The vast diversity of microbial species, and their ability to break a wide range of chemical bonds, means that they are responsible for many key soil functions including:
Archive | 2009
K. W. T. Goulding; Elizabeth A. Stockdale; Christine A. Watson
Effective nutrient management is essential in organic farming systems. Processed soluble fertilisers such as ammonium nitrate, which feed the plant directly and are thought to bypass the natural processes of the soil, are not generally acceptable. Nutrient supply to crop plants is supported through recycling, the management of biologically-related processes such as nitrogen fixation by clover and other legumes, and the limited use of unrefined, slowly-soluble off-farm materials that decompose in the same way as soil minerals or organic matter. The aim is to achieve as far as possible a closed nutrient cycle on the farm and to minimise adverse environmental impact. Effective management of any ‘waste’ materials such as manures and crop residues is a key to nutrient cycling on organic farms. However, not all organic farms have easy access to manures and recycling is limited by the prohibition of the use of sewage sludge because of current concerns over the introduction of potentially toxic elements, organic pollutants and disease transmission. In addition, the current global market, in which food is transported large distances from the farm, results in a significant export of nutrients. Exported nutrients must be replaced to avoid nutrient depletion of soils. Nutrient budgeting suggests some cause for concern over the sustainability of organic systems because of their dependence on feedstuffs and bedding for inputs of phosphorus (P) and potassium (K), and on the very variable fixation by legumes or imports of manure or compost for nitrogen (N); air pollution and net mineralisation from soil reserves appear to comprise a large part of the N supply on some organic farms. Losses of N from organic systems can also be as large as those from conventional systems and, being dependent on cultivation and the weather, they are even more difficult to control than those from fertilisers applied to conventional farms. There is some evidence of P deficiency in soils under organic production, and replacing K sold off the farm in produce is especially difficult. Organic farming systems may be sustainable and have the potential to deliver significant environmental benefits, but these depend on specific cropping and management practices on each farm. It is important that we study and improve nutrient management on all farm systems and in the context of plant, animal and human health in order to develop more sustainable farming systems.
Soil Biological Fertility, A Key to Sustainable Land Use in Agriculture | 2007
Elizabeth A. Stockdale; W. Richard Cookson
The term ‘sustainable agriculture’ is used widely and has embraced a diverse range of issues and objectives, including animal welfare, greater protection of the environment, and the need for farming to support other sectors of the economy such as tourism. Where the principles of sustainable development are applied to agriculture, then farming systems are judged to make a major input to a sustainable economy and society when they concurrently meet the following objectives: • Produce safe food and non-food products in response to market demands. • Enable viable livelihoods to be made from land management. • Operate within biophysical constraints and enable a diverse wildlife. • Provide environmental and other benefits to the public such as recreation and access. • Achieve the highest standards of animal health and welfare.
Soil Biology & Biochemistry | 2007
William Cookson; M. Osman; Petra Marschner; D.A. Abaye; Ian Clark; Daniel V. Murphy; Elizabeth A. Stockdale; C.A. Watson
Soil Biology & Biochemistry | 2005
William Cookson; Daniel A. Abaye; Petra Marschner; Daniel V. Murphy; Elizabeth A. Stockdale; Keith Goulding
Agronomie | 2002
Elizabeth A. Stockdale; D. J. Hatch; Daniel V. Murphy; Stewart Ledgard; Catherine J. Watson
European Journal of Soil Science | 2007
Daniel V. Murphy; Elizabeth A. Stockdale; P. R. Poulton; T.W. Willison; K. W. T. Goulding
Water, Air, & Soil Pollution: Focus | 2004
Victoria B. Willett; James J. Green; Andy Macdonald; John A. Baddeley; Georg Cadisch; Steven M. J. Francis; K. W. T. Goulding; Gary Saunders; Elizabeth A. Stockdale; Christine A. Watson; Davey L. Jones