Publications

Consensus recommendations call for the elimination of lactate dehydrogenase (LDH) tests from routine rule out myocardial infarction (ROMI) protocols.We conducted a utilization review project in which we evaluated the institutional impact of removing LDH and LDH isoenzyme tests from our hospital diagnostic panel. We then conducted a scripted telephone survey of 100 US hospitals to assess the generalizability of this project.All our cardiology staff members supported this intervention. Lactate dehydrogenase isoenzyme test results did not add clinically useful data for any of 200 consecutive patients discharged with a diagnosis of acute myocardial infarction, and selective use of LDH isoenzyme testing in cases where it was clinically believed to be indicated cut costs 99% during the year after our intervention. Furthermore, our telephone survey demonstrated that 66% of US hospitals polled continue to test for LDH isoenzymes in every patient with possible myocardial infarction.Our results corroborate prior recommendations for the removal of LDH testing from the routine ROMI protocol. Such an intervention may be accomplished easily, with excellent staff acceptance and considerable savings. Most US hospitals continue to include LDH testing in their ROMI panels despite national guidelines recommending otherwise.

No abstract is provided for this article.

The need for increased food production to support the growing global population requires more efficient nutrient management and prevention of nitrogen (N) losses from both applied fertiliser and organic matter (OM) decomposition. This is particularly important in semi-arid rainfed cropping soils, where soil water and temperature are the dominant drivers of N cycling rather than agricultural management. Here we used 14C and 15N techniques to examine how peptide/amino acid turnover, gross and net N transformation rates and nitrous oxide (N2O) emissions responded to long-term plant residue additions and/or short-term root exudate additions. Soil was collected from a semi-arid rainfed field trial with one winter crop per year followed by a summer fallow period, where additional inputs of straw/chaff over 10 years had increased total soil organic C (SOC) by 76% compared to no extra additions (control). These field soils were incubated in the laboratory with or without a synthetic root exudate mixture at a range of temperatures reflecting regional field conditions (5–50 °C). Long-term plant residue additions (to build up total soil OM) did not decrease the risk of N loss as defined by the nitrification:immobilisation (N:I) ratio at most temperatures, so was not an effective management tool to control N losses. In comparison, short-term root exudate additions decreased the risk of N loss at all temperatures in both the control and plant residue treatment field soils. Increased net N mineralisation and decreased microbial C use efficiency at temperatures greater than 30 °C resulted in significant ammonium (NH4+) accumulation. Microbial decomposers appeared to use amino acid-C for growth but peptide-C for energy production. Findings indicate that the greatest risk of N loss in these semi-arid soils will occur during rains at the start of the growing season, due to inorganic N accumulation over summer fallow when there are high soil temperatures, occasional significant rainfall events and no growing plants to release root exudates. While most attempts to manipulate the soil N cycle have occurred during the winter cropping period, our findings highlight the need to manage N supply during summer fallow if we are to minimise losses to the environment from semi-arid soils.

The temporal dynamics of partitioning and rhizodeposition of recent photosynthate in wheat (Triticum aestivum) roots were quantified in situ in solution culture. After a 30-min pulse of 14CO2 to a single intact leaf, 14C activities of individual carbon fluxes in the root, including exudation, respiration, and root content, were measured continuously over the next 20 h concurrently with 14C efflux from the leaf. Immediately after the end of the 14CO2 pulse, 14C activity was detected in the root, the hydroponic solution, and in root respiration. The rate of 14C exudation from the root was maximal after 2 to 3 h, and declined to one-third of maximum after a further 5 h. Completion of the rapid phase of 14C efflux from the leaf coincided with peak 14C exudation rate. Thus, exudation flux is much more rapidly and dynamically coupled to current photosynthesis than has been appreciated. Careful cross-calibration of 14C counting methods allowed a dynamic 14C budget to be constructed for the root. Cumulative 14C exudation after 20 h was around 3% of 14C fixed in photosynthesis. Partitioning of photosynthate between shoot and root was manipulated by partial defoliation before applying the 14CO2 pulse to the remaining intact leaf. Although the rate of photosynthesis was largely unaffected by partial defoliation, the proportion of new photosynthate subsequently partitioned to and exuded from the root was substantially reduced. This clearly indicates that exudation depends more on the rate of carbon import into the root than on the rate of photosynthesis.

Extensively grazed grasslands are understudied in terms of their contribution to greenhouse gas (GHG) emissions from livestock production. Mountains, moorlands and heath occupy 18% of the UK land area, however, in situ studies providing high frequency N2O emissions from sheep urine deposited to such areas are lacking. Organic soils typical of these regions may provide substrates for denitrification-related N2O emissions, however, acidic and anoxic conditions may inhibit nitrification (and associated emissions from nitrification and denitrification). We hypothesised urine N2O-N emission factors (EFs) would be lower than the UK country-specific and IPCC default value for urine, which is based on lowland measurements. Using automated GHG sampling chambers, N2O emissions were determined from real sheep urine (930 kg N ha−1) and artificial urine (920 kg N ha−1) applied in summer, and from an artificial urine treatment (1120 kg N ha−1) and a combined NO3− and glucose treatment (106 kg N ha−1; 213 kg C ha−1) in autumn. The latter treatment provided an assessment of the soils capacity for denitrification under non-substrate limiting conditions. The artificial urine-N2O EF was 0.01 ± 0.00% of the N applied in summer and 0.00 ± 0.00% of the N applied in autumn. The N2O EF for real sheep urine applied in summer was 0.01 ± 0.02%. A higher flux was observed in only one replicate of the real urine treatment, relating to one chamber where an increase in soil solution NO3− was observed. No lag phase in N2O emission was evident following application of the NO3− and glucose treatment, which emitted 0.69 ± 0.15% of the N applied. This indicates nitrification rates are the bottle-neck for N2O emissions in upland organic soils. We calculated the potential impact of using hill-grazing specific urine N2O EFs on the UK inventory of N2O emissions from sheep excreta, and found a reduction of ca. 43% in comparison to the use of a country-specific excretal EF.

The short and long term influence of depleted uranium (DU) on soil microbial populations remains largely understudied. To understand short term effect of DU on soil microbial activity, an incubation study was conducted using 14C-labeled glucose. Two soils of...

No abstract is provided for this article.

The release of root exudates into the rhizosphere is known to enhance soil biological activity and alter microbial community structure. To assess whether r

It is now widely acknowledged that microplastic pollution represents one of the greatest anthropogenically mediated threats to Earth-system functioning. In freshwater and marine ecosystems the presence of large amounts of microplastic appears almost ubiquitous, with frequent reports of negative impacts on aquatic health. In contrast, however, the impact of plastic in terrestrial environments remains poorly understood. In agroecosystems, microplastics (particles < 5 mm) can enter the soil environment either directly (e.g. from biosolids application, irrigation water, atmospheric deposition), or indirectly through the in situ degradation of large pieces of plastic (e.g. from plastic mulch films). Although we have encouraged the use of plastics over the last 50 years in agriculture to promote greater resource use efficiency and food security, the legacy of this is that many soils are now contaminated with large amounts of plastic residue (ca. 50–250 kg ha−1). Due to difficulties in separating and quantifying plastic particles from soil, our knowledge of their behavior, fate and potential to transfer to other receptors (e.g. surface and groundwater, air) and enter the human food chain remains poor. This information, however, is critical for evaluating the risk of soil-borne microplastic pollution. In this critical review, we systematically summarize (i) the distribution and migration of microplastics in soils, (ii) highlight the separation, extraction, and identification methods for monitoring microplastics in soils, (iii) discuss the ecological effects and pollution mechanisms of soil microplastics, (iv) propose mitigation strategies to help prevent and reduce microplastic pollution, and (v) identify the most important future challenges in soil microplastics research.

No abstract is provided for this article.

No abstract is provided for this article.

Exudation of organic acid anions by plants as well as root-induced changes in rhizosphere pH can potentially improve phosphate (Pi) availability in the rhi

It is now a century since Hiltner first formulated the concept of the rhizosphere and introduced the term to the vocabulary of soil science. The concept has attracted interest from diverse fields, each with its own operational definition. Initially only of interest to soil microbiologists, it was then taken up by soil chemists, later physicists, and is now again an important theme in soil microbiology with its new molecular tools. One of the major hurdles that research on the rhizosphere has had to overcome is the difficulty in sampling such an inherently inaccessible zone. Often sampling modifies the system, and when gradients are steep and relations non-linear, important effects can be overlooked if sampling averages across too large a space. Major advances in understanding have been made when sampling and measurements are miniaturized and when mathematical models are used alongside experimental approaches. Studies of the rhizosphere require old boundaries between the traditional subdisciplines of soil science to be rethought. Plants and microorganisms are not passive sinks for nutrients and pollutants; they modify their environment and influence their exposures to both essential and potentially toxic elements. Soil is increasingly recognized to be a heterogeneous and dynamic medium across all spatial and temporal scales applied to it. Experimental and modelling approaches that ignore this are bound to be inadequate. Good ideas are rarely isolated, and when the Journal was approached by the organisers of the conference, Rhizosphere: Perspectives and Challenges – A Tribute to Lorentz Hiltner, held in Munich in September 2004, we had already decided to publish an issue on the rhizosphere to mark Hiltner's centenary. This issue gives a selection of the communications presented at that conference. We hope it provides a representative sample of current work on the rhizosphere that is within the scope of the Journal, and indicates future research needs and priorities. Further communications from the Conference appear in Biology and Fertility of Soils, Environmental Microbiology, FEMS Microbiology Ecology, The New Phytologist, Journal of Plant Nutrition & Soil Science, Journal of Environmental Quality and Plant and Soil.

No abstract is provided for this article.