Environmental aspects of soil phosphorus testing

peer-reviewedSoil phosphorus testing in Ireland uses Morgan’s reagent from samples taken to 10 cm depth for agronomic recommendations. However, its suitability as an environmental indicator has been questioned in terms of sample depth and extraction solution. Seven grassland sites were sampled to depths of 2, 5 and 10 cm and extracted for Morgan’s P, the standard agronomic test, as well as iron-oxide impregnated paper strip P (FeOP), calcium chloride extractable P (CaCl2-P) and water soluble P (WSP), all proposed as environmental soil tests. Extractable soil P decreased with increasing sample depth, as did variances in each test, such that, 2 cm samples had highest concentrations and variances. The current standard sample depth (10 cm) was linearly related to corresponding data from samples taken to 2 and 5 cm, indicating that surface soil P can be consistently estimated from the current standard depth. When soil tests were compared with dissolved reactive P (DRP) in overland flow collected from two field sites, certain soil tests were better indicators of P loss than others. The relative difference in Morgan’s P values at the standard sample depth (10 cm) was reflected in the relative difference in P loss between the two sites. Average values of DRP collected from two sites ranged from 0.032 to 0.067 mg/l at the low P site and 0.261 to 0.620 at the high P site. Average DRP values from the high P site and maximum DRP values from the low P site were simulated using water-soluble P extraction at water to soil ratios 5 to 250 l/kg. In this study, Morgan’s P to 10 cm gave a good indication of the relative difference in DRP loss between the two sites

Evaluating Morgan’s Phosphorus Test as an Environmental Indicator

End of Project ReportThis project was part-funded by the EPA RTDI programmePhosphorus loss from soil to water is a major component of surface water pollution in Ireland and water quality reports from the EPA have shown an increasing upwards trend in slight and moderate pollution often attributed to agricultural phosphorus (P). There is a need therefore for indicators of P loss from agriculture that might predict areas vulnerable to P loss. Soil test P is a typical parameter often used in risk assessment and catchment modeling and although originally designed as an agronomic indicator of P requirements for crop growth, it is often used to indicate risk of P loss from agricultural areas. Soil phosphorus (P) testing in Ireland uses Morgan's reagent from samples taken to 10cm depth for agronomic recommendations, however, it's sustainability as an environmental indicator has been questioned in terms of sample depth and extraction solution. In this study, seven grassland sites were sampled to 2, 5 and 10cm depths and extracted for Morgan's P, the standard agronomic test, as well as, iron-oxide impregnated paper strip P (FeO-P), calcium chloride extractable P (CaCl2-P)and water soluble P (WSP), all proposed as environmental soil tests. Extractable soil P increased with decreasing sample depth, as did variances in each test, such that, 2 cm samples had highest concentrations and variances. The current standard sample depth (10cm) was linearly correlated with corresponding data from samples taken to 2 and 5cm, indicating that surface soil P can be consistently estimated from the current standard depth. When soil tests were compared with Dissolved reactive P (DRP) in overland flow collected from field studies, certain soil tests were better indicators of P loss than others. The relative difference in Morgan's P values at the standard sample depth (10cm) was reflected in the relative difference in P loss between the two sites. Values of DRP collected from two sites ranged from 0.032-0.67 mg/l at the low P site and 0.261-0.620 at the high P site. Average DRP values from the high P site and maximum DRP values from the low P site were simulated using water-soluble P extracts. In this study, Morgan's P to 10cm gave a good indication of the relative difference in DRP loss between the two sites.Environmental PRotection Agenc

Evaluating Morgan’s Phosphorus Test as an Environmental Indicator

End of Project ReportThis project was part-funded by the EPA RTDI programmePhosphorus loss from soil to water is a major component of surface water pollution in Ireland and water quality reports from the EPA have shown an increasing upwards trend in slight and moderate pollution often attributed to agricultural phosphorus (P). There is a need therefore for indicators of P loss from agriculture that might predict areas vulnerable to P loss. Soil test P is a typical parameter often used in risk assessment and catchment modeling and although originally designed as an agronomic indicator of P requirements for crop growth, it is often used to indicate risk of P loss from agricultural areas. Soil phosphorus (P) testing in Ireland uses Morgan's reagent from samples taken to 10cm depth for agronomic recommendations, however, it's sustainability as an environmental indicator has been questioned in terms of sample depth and extraction solution. In this study, seven grassland sites were sampled to 2, 5 and 10cm depths and extracted for Morgan's P, the standard agronomic test, as well as, iron-oxide impregnated paper strip P (FeO-P), calcium chloride extractable P (CaCl2-P)and water soluble P (WSP), all proposed as environmental soil tests. Extractable soil P increased with decreasing sample depth, as did variances in each test, such that, 2 cm samples had highest concentrations and variances. The current standard sample depth (10cm) was linearly correlated with corresponding data from samples taken to 2 and 5cm, indicating that surface soil P can be consistently estimated from the current standard depth. When soil tests were compared with Dissolved reactive P (DRP) in overland flow collected from field studies, certain soil tests were better indicators of P loss than others. The relative difference in Morgan's P values at the standard sample depth (10cm) was reflected in the relative difference in P loss between the two sites. Values of DRP collected from two sites ranged from 0.032-0.67 mg/l at the low P site and 0.261-0.620 at the high P site. Average DRP values from the high P site and maximum DRP values from the low P site were simulated using water-soluble P extracts. In this study, Morgan's P to 10cm gave a good indication of the relative difference in DRP loss between the two sites.Environmental PRotection Agenc

A rapid and multi-element method for the analysis of major nutrients in grass (Lolium perenne) using energy-dispersive X-ray fluorescence spectroscopy

peer-reviewedElemental analysis of grass (Lolium perenne) is essential in agriculture to ensure grass quality and animal health. Energy-dispersive X-ray fluorescence (EDXRF) spectroscopy is a rapid, multi-element alternative to current methods using acid digestion and inductively coupled plasma optical emission spectrometry (ICP-OES). Percentage phosphorus (P), potassium (K), magnesium (Mg) and calcium (Ca), determined from grass samples using EDXRF, were within 0.035, 0.319, 0.025 and 0.061, respectively, of ICP-OES values. Concordance correlation coefficients computed using agreement statistics ranged from 0.4379 to 0.9669 (values close to one indicate excellent agreement); however, the level of agreement for each element depended on the calibrations used in EDXRF. Empirical calibrations gave excellent agreement for percentage P, K and Ca, but moderate agreement for percentage Mg due to a weaker correlation between standards and intensities. Standardless calibration using the fundamental parameters (FP) approach exhibited bias, with consistently lower values reported for percentage P and Mg, when compared with ICP-OES methods. The relationship between the methods was plotted as scatter plots with the line of equality included, and although correlation coefficients indicated strong relationships, these statistics masked the effects of consistent bias in the data for percentage P and Mg. These results highlight the importance of distinguishing agreement from correlation when using statistical methods to compare methods of analysis. Agreement estimates improved when a matching library of grass samples was added to the FP method. EDXRF is a comparable alternative to conventional methods for grass analysis when samples of similar matrix type are used as empirical standards or as a matching library

Early Outcomes for Programs and Families in Children's Futures

Assesses the programmatic achievements and outcomes for families in the first five years of a community change initiative providing an array of social services. Discusses lessons learned and issues of cost, partnership development, and sustainability

Atypical Listeria innocua strains possess an intact LIPI-3

peer-reviewedBackground: Listeria monocytogenes is a food-borne pathogen which is the causative agent of listeriosis and can be divided into three evolutionary lineages I, II and III. While all strains possess the well established virulence factors associated with the Listeria pathogenicity island I (LIPI-1), lineage I strains also possess an additional pathogenicity island designated LIPI-3 which encodes listeriolysin S (LLS), a post-translationally modified cytolytic peptide. Up until now, this pathogenicity island has been identified exclusively in a subset of lineage I isolates of the pathogen Listeria monocytogenes. Results: In total 64 L. innocua strains were screened for the presence of LIPI-3. Here we report the identification of an intact LIPI-3 in 11 isolates of L. innocua and the remnants of the cluster in several others. Significantly, we can reveal that placing the L. innocua lls genes under the control of a constitutive promoter results in a haemolytic phenotype, confirming that the cluster is capable of encoding a functional haemolysin. Conclusions: Although the presence of the LIPI-3 gene cluster is confined to lineage I isolates of L. monocytogenes, a corresponding gene cluster or its remnants have been identified in many L. innocua strains.This work was funded by the Enterprise Ireland Commercialisation fund, a programme which is co-financed by the EU through the ERDF. This work was also supported by the Irish Government under the National Development Plan, through Science Foundation Ireland Investigator awards; (06/IN.1/B98) and (10/IN.1/B3027)

Efficacy of nisin A and nisin V semi-purified preparations alone and in combination with plant essential oils to control Listeria monocytogenes

peer-reviewedThe foodborne pathogenic bacterium Listeria is known for relatively low morbidity and high mortality rates reaching up to 25-30%. Listeria is a hardy organism and its control in foods represents a significant challenge. Many naturally occurring compounds, including the bacteriocin nisin and a number of plant essential oils, have been widely studied and are reported to be effective as antimicrobial agents against spoilage and pathogenic microorganisms. The aim of this study was to investigate the ability of semi-purified preparations (spp) containing either nisin A or an enhanced bioengineered derivative nisin V, alone and in combination with low concentrations of the essential oils thymol, carvacrol and trans-cinnamaldehyde, to control L. monocytogenes in both laboratory media and model food systems. Combinations of nisin V-containing spp (25 μg/ml) with thymol (0.02%), carvacrol (0.02%) or cinnamaldehyde (0.02%) produced a significantly longer lag phase than any of the essential oil/nisin A combinations. In addition, the log reduction in cell counts achieved by the nisin V + carvacrol or nisin V + cinnamaldehyde combinations was twice that of the equivalent nisin A + essential oil treatment. Significantly, this enhanced activity was validated in model food systems against L. monocytogenes strains of food origin. We conclude that the fermentate form of nisin V in combination with carvacrol and cinnamaldehyde offers significant advantages as a novel, natural and effective means to enhance food safety by inhibiting foodborne pathogens such as L. monocytogenes.This work was supported by the Irish Government under the National Development Plan, through Science Foundation Ireland Investigator awards to C.H. and R.P.R. (10/IN.1/B3027), and C.H., R.P.R. and P.D.C. (06/IN.1/B98)

Agriculture, meteorology and water quality in Ireland: a regional evaluation of pressures and pathways of nutrient loss to water

peer-reviewedThe main environmental impact of Irish agriculture on surface and ground water quality is the potential transfer of nutrients to water. Soil water dynamics mediate the transport of nutrients to water, and these dynamics in turn depend on agro-meteorological conditions, which show large variations between regions, seasons and years. In this paper we quantify and map the spatio-temporal variability of agro-meteorological factors that control nutrient pressures and pathways of nutrient loss. Subsequently, we evaluate their impact on the water quality of Irish rivers. For nitrogen, pressure and pathways factors coincide in eastern and southern areas, which is reflected in higher nitrate levels of the rivers in these regions. For phosphorus, pathway factors are most pronounced in north-western parts of the country. In south-eastern parts, high pressure factors result in reduced biological water quality. These regional differences require that farm practices be customised to reflect the local risk of nutrient loss to water. Where pathways for phosphorus loss are present almost year-round—as is the case in most of the north-western part of the country—build-up of pressures should be prevented, or ameliorated where already high. In south-eastern areas, spatio-temporal coincidence of nutrient pressures and pathways should be prevented, which poses challenges to grassland management

Bioengineered Nisin A Derivatives with Enhanced Activity against Both Gram Positive and Gram Negative Pathogens

peer-reviewedNisin is a bacteriocin widely utilized in more than 50 countries as a safe and natural antibacterial food preservative. It is the most extensively studied bacteriocin, having undergone decades of bioengineering with a view to improving function and physicochemical properties. The discovery of novel nisin variants with enhanced activity against clinical and foodborne pathogens has recently been described. We screened a randomized bank of nisin A producers and identified a variant with a serine to glycine change at position 29 (S29G), with enhanced efficacy against S. aureus SA113. Using a site-saturation mutagenesis approach we generated three more derivatives (S29A, S29D and S29E) with enhanced activity against a range of Gram positive drug resistant clinical, veterinary and food pathogens. In addition, a number of the nisin S29 derivatives displayed superior antimicrobial activity to nisin A when assessed against a range of Gram negative food-associated pathogens, including E. coli, Salmonella enterica serovar Typhimurium and Cronobacter sakazakii. This is the first report of derivatives of nisin, or indeed any lantibiotic, with enhanced antimicrobial activity against both Gram positive and Gram negative bacteria.This work was supported by the Irish Government under the National Development Plan, through Science Foundation Ireland Investigator awards (10/IN.1/B3027) and (06/IN.1/B98) (http://www.sfi.ie)

Listeriolysin S, a Novel Peptide Haemolysin Associated with a Subset of Lineage I Listeria monocytogenes

peer-reviewedStreptolysin S (SLS) is a bacteriocin-like haemolytic and cytotoxic virulence factor that plays a key role in the virulence of Group A Streptococcus (GAS), the causative agent of pharyngitis, impetigo, necrotizing fasciitis and streptococcal toxic shock syndrome. Although it has long been thought that SLS and related peptides are produced by GAS and related streptococci only, there is evidence to suggest that a number of the most notorious Gram-positive pathogenic bacteria, including Listeria monocytogenes, Clostridium botulinum and Staphylococcus aureus, produce related peptides. The distribution of the L. monocytogenes cluster is particularly noteworthy in that it is found exclusively among a subset of lineage I strains; i.e., those responsible for the majority of outbreaks of listeriosis. Expression of these genes results in the production of a haemolytic and cytotoxic factor, designated Listeriolysin S, which contributes to virulence of the pathogen as assessed by murine- and human polymorphonuclear neutrophil–based studies. Thus, in the process of establishing the existence of an extended family of SLS-like modified virulence peptides (MVPs), the genetic basis for the enhanced virulence of a proportion of lineage I L. monocytogenes may have been revealed.Work is funded by the Irish Government under the National Development Plan, through a Science Foundation Ireland Investigator award to CH, PR and PC (06/IN.1/B98)