Manipulating geological phosphorus resources for improved production and environmental outcomes during plant establishment.

Phosphorus (P) fertilisers are under scrutiny due to resource constraints and environmental impacts. Simple rock phosphate (RP) modifications with acids and co-applied with microbial inoculum could offer sustainable alternative P fertiliser products. We evaluated the effects of acid-treated rock phosphate (RP) in combination with fungal inoculum on plant establishment, environmental impacts (nutrient leaching) and soil quality in a 5-month pot trial. The treatments were evaluated in a clayey Vertisol and a silty Acrisol using cotton (Gossypium hirsutum) as a model plant. The RP treatments - apart from the unmodified and HCl products - were effective in promoting plant establishment with two of the microbial formulations superior to conventional P fertilisers by an average factor of 2 in both soil types (p < 0.05). All RP products restricted P leaching compared with conventional P fertilisers (p < 0.05), by an average factor of 5 for diammonium phosphate (DAP) in both soil types and 3 for the triple superphosphate TSP (only in Acrisol). Nitrate leaching from all treatments was high although much lower from the RP treatments compared with the conventional fertilisers towards the end of the establishment trial, by an average factor of 1.5 (p < 0.05). Ranking analysis revealed that some RP treatments showed evidence for improved ongoing soil quality, including decreased P leaching and soil acidification risks. Microbial analysis showed complex interactions between treatment and soil type. Nonetheless, inoculum persistence at the end of the plant establishment phase was observed for all pots analysed. Our results demonstrate that relatively simple modifications to RP could pave the way for developing sustainable P fertilisers.

Replacing alfalfa hay with a novel alfalfa leaf pellet product (ProLEAF MAX) and/or alfalfa stems (ProFiber Plus) in the diet of developing dairy heifers alters dry matter intake, but does not negatively impact growth or development.

Alfalfa is a commonly grown forage in the Intermountain West region of the United States and is often included in the diet of dairy cattle. Alfalfa provides a variety of different nutrients, but the nutrient content of alfalfa varies depending on factors such as the soil, region, cutting, and climate. However, alfalfa leaves tend to have less variation in their nutrient content than alfalfa stems. Fractionating alfalfa may be one way to improve control of nutrients provided when developing a ration for developing dairy heifers. The purpose of this study was to determine whether including fractionated alfalfa in the diet impacts the growth or conception rates of developing dairy heifers. Heifers were allocated to one of three treatments: a control group fed a typical diet (CON; n = 8), a diet that replaced alfalfa with fractionated alfalfa leaf pellets and alfalfa stems (ProLEAF MAX + ProFiber Plus; PLM + PFP; n = 8), or a diet that replaced alfalfa with alfalfa stems (PFP; n = 8) for 85 d. Heifers were fed individually twice daily and weight, hip height (HH), and wither height (WH) were recorded every 14 d. Additionally, blood was collected every 28 d, and conception rates were recorded at the end of the trial. Heifers receiving the PFP diet consumed less dry matter (P = 0.001) than the CON treatment. Analyses were then conducted to determine nutrient intake and heifers receiving the PFP diet also consumed less neutral detergent fiber (P = 0.02), acid detergent fiber (P = 0.02), crude protein (P = 0.001), and net energy for maintenance (P = 0.001) than heifers consuming the CON diet; however, no differences (P > 0.10) were observed between heifers fed the CON and PLM + PFP diets. Analysis of body weight gain over the feeding period showed no difference (P = 0.52) among heifers consuming the different treatment diets. Additionally, treatment did not affect average daily gain (P = 0.49), gain:feed (P = 0.82), HH gain (P = 0.20), or WH gain (P = 0.44) among heifers receiving different diets. Treatment × time altered (P < 0.001) blood urea nitrogen when analyzed as a repeated measure. Total feed cost was lowest (P < 0.001) for the PFP diet and cost of gain tended (P = 0.09) to be increased for the PLM + PFP diet compared to the CON diet. Overall, these data indicate that including alfalfa stems in a developing heifer diet may decrease dry matter intake, lower input costs, and increase profitability, without negatively impacting growth.

'Climate Healing Stones': Common Minerals Offer Substantial Climate Change Mitigation Potential.

This review proposes that mineral-based greenhouse gas (GHG) mitigation could be developed into a substantial climate change abatement tool. This proposal was evaluated via three objectives: (1) synthesise literature studies documenting the effectiveness of geological minerals at mitigating GHG emissions; (2) quantify, via meta-analysis, GHG magnitudes that could be abated by minerals factoring-in the carbon footprint of the approach; and (3) estimate the global availability of relevant minerals. Several minerals have been effectively harnessed across multiple sectors-including agriculture, waste management and coal mining-to mitigate carbon dioxide/CO2 (e.g., olivine), methane/CH4 (e.g., allophane, gypsum) and nitrous oxide/N2O (e.g., vermiculite) emissions. High surface area minerals offer substantial promise to protect soil carbon, albeit their potential impact here is difficult to quantify. Although mineral-based N2O reduction strategies can achieve gross emission reduction, their application generates a net carbon emission due to prohibitively large mineral quantities needed. By contrast, mineral-based technologies could abate ~9% and 11% of global CO2 and CH4 anthropogenic emissions, respectively. These estimates conservatively only consider options which offer additional benefits to climate change mitigation (e.g., nutrient supply to agricultural landscapes, and safety controls in landfill operations). This multi-benefit aspect is important due to the reluctance to invest in stand-alone GHG mitigation technologies. Minerals that exhibit high GHG mitigation potential are globally abundant. However, their application towards a dedicated global GHG mitigation initiative would entail significant escalation of their current production rates. A detailed cost-benefit analysis and environmental and social footprint assessment is needed to ascertain the strategy's scale-up potential.

Plastic pollution risks in bioretention systems: a case study.

We investigated plastic pollution in soil-based stormwater bioretention systems (BRS), which are potentially important pollutant receptors and pathways. Our integrated study is the first of its kind, focusing on plastic abundance, size fractionation, composition, and interactions with urban metrics (including housing density and auxiliary stormwater treatment infrastructure) in BRS filter media. Our results revealed that mesoplastic (MEP) and microplastic (MP) concentrations in BRS are comparable with those reported in other stormwater systems (e.g. wetlands) as well as soils in other land use areas (e.g. agriculture). Distributional sampling within the BRS revealed MP abundances do not change with horizontal distance from the inlet to the outlet. However, MEP abundances drastically decreased towards the outlet, indicating plastic accumulation within BRS. This is important because MEPs can breakdown into MPs which can affect BRS function as well as mobilise downstream. Yet our data uncovered more complex mechanisms involved in BRS plastic fate, with composition data revealing that MPs are not simply breakdown products of MEPs but are instead derived from different sources. Composition, morphology and colour analysis confirmed that BRS polymer liners are a key source of MPs and MEPs in soil filter media. Multivariate analysis of the data with urban design metrics showed gross pollutant traps are effective at decreasing MP concentrations in BRS but not as effective at controlling MEPs. Our results point to complex plastic transmission and accumulation pathways in BRS. Interception measures can partially alleviate plastic risk, but more work is needed to elucidate plastic long-term fate in BRS.

Enzymatic purification of microplastics in soil.

Accurate and effective analysis of microplastics depends on the purification of any biogenic matter present in the environmental sample. Within the soil environment, the presence of biogenic materials (living and non-living) obstruct reliable identification of microplastics. However, while conventional acidic, alkaline, and wet peroxidation methods are often used for microplastics purification, they can result in significant alteration to the polymer integrity. To overcome this issue of polymer damage, we have developed a more efficient protocol using enzymes to eliminate organic materials from soil media without affecting the synthetic polymers. This method describes a simple enzymatic protocol that eliminates the organic matter based on the application of enzymes that target the three natural components of lignocellulosic biomass (cellulose, hemicellulose, and lignin). The enzymatic protocol introduced in this study allows for the use of an oxidizing agent for the pre-treatment of samples and density separation step. Additionally, this method was used to determine the enzymatic digestion efficiencies of soil organic matter and recovery rates of microplastics. Finally, the recovered microplastics were characterized by techniques including stereomicroscopy, FT-IR, and SEM. This method proved to be effective in reducing approximately >90% of organic materials in soil samples. After showing a high digestion efficiency the method was applied to spiked microplastic soil samples where high recovery rates were established and plastic characteristics were conserved. Despite being a time consuming and expensive method when compared to other purification methods. The key benefits of this methodology are:•Minimal sample preparation•Representative purification of microplastic from diverse soil media; and•Most importantly, preservation of polymer integrity aiding requirements needed for particle identification (e.g.,% mass polymer remaining, SEM images revealing no obvious polymer morphology change after enzyme treatment).

Effects of feeding a novel alfalfa leaf pellet product (ProLEAF MAX) and alfalfa stems (ProFiber Plus) on performance in the feedlot and carcass quality of beef steers.

Alfalfa is often included in the diets of beef animals; however, the nutrient content of alfalfa is variable depending on the region in which it is grown, climate, soil, and many other factors. The leaf portion of alfalfa has a less variable nutrient composition than the stem portion of the plant. The variability that is present in the alfalfa plant can make the development of total mixed rations of consistent nutrient content difficult. As such, the purpose of this study was to determine how the inclusion of fractionated alfalfa leaves and alfalfa stems impacts performance and carcass quality of finishing beef steers. Twenty-four steers were allocated to one of three treatments: a control group fed a typical finishing diet with alfalfa as the forage (CON; n = 8), a typical diet that replaced alfalfa with fractionated alfalfa leaf pellets and alfalfa stems (ProLEAF MAX™ + ProFiber Plus™; PLM+PFP; n = 8), or a typical diet that replaced alfalfa with alfalfa stems (PFP; n = 8) for 63 days. Steers were fed individually once daily, weighed every 14 days and ultrasound images were collected every 28 days. At the end of the feeding trial, steers were harvested at a commercial facility and carcass data was obtained. Analysis of dry matter intake demonstrated that steers receiving the PFP and CON diets consumed more feed (P < 0.001) than steers consuming the PLM+PFP diet. Steers receiving the PLM+PFP diet gained less (P < 0.001) weight than the steers receiving the other two dietary treatments. No differences (P > 0.10) in feed efficiency or carcass characteristics were observed. Steers receiving the PFP diet had improved (P = 0.016) cost of gain ($0.93 per kg) when compared with steers receiving PLM+PFP ($1.08 per kg) diet. Overall, our findings demonstrate that the inclusion of PFP in place of alfalfa hay in a finishing diet has the potential to improve cost of gain, without negatively affecting growth, performance, or carcass characteristics of finishing feedlot steers.

The rise of artificial soil carbon inputs: Reviewing microplastic pollution effects in the soil environment.

The surge in the use of plastic materials, its poor handling and disposal have led to an increase in microplastic pollution in terrestrial environments. Microplastic pollution in soils is of concern due to potential influences on soil properties which play a critical role in plant growth and soil fertility. Moreover, the soil environment is a key nexus linking the atmosphere, hydrosphere, biosphere and lithosphere, and thus represents a crucial conduit for pollutant migration from the anthroposphere. In this review we evaluate the effects of microplastics in the soil environment with a specific focus on physical properties and biological function in the rhizosphere. Our review reveals that agricultural sources, particularly plastic mulches and waste applications, represent the main source of soil microplastic inputs. Once in the soil environment, microplastic effects on soil properties are highly variable depending mainly on soil type and microplastic characteristics. Soil properties relating to erosion-risk (i.e., bulk density), structural integrity (i.e., aggregate stability, particularly micro-aggregate stability), and water-storage capacity (i.e., evaporation rate, desiccation) are generally adversely impacted by soil microplastic inputs. Soil microplastic effects on rhizosphere function (i.e., plant health and microbial activity) are remarkably varied with some studies revealing positive impacts, such as enhanced plant-symbiotic fungi associations, from soil plastic additions. However, all identified publications reported at least one detrimental MP-induced impact on plant responses. Finally, our review revealed associations between microplastic properties and soil functional parameters - in particular, polymer size and morphology control soil water-holding properties whereas polymer type influences plant response. These associations will be helpful in targeting future research directions on this important topic that intersects all of the Earth's spheres.

Designing for effective controlled release in agricultural products: new insights into the complex nature of the polymer-active agent relationship and implications for use.

BACKGROUND: Various active chemical agents, such as soil microbial inhibitors, are commonly applied to agricultural landscapes to optimize plant yields or minimize unwanted chemical transformations. Dicyandiamide (DCD) is a common nitrification inhibitor. However, it rapidly decomposes under warm and wet conditions, losing effectiveness in the process. Blending DCD with an encapsulating polymer matrix could help overcome this challenge and slow its release. Here, we encapsulated DCD in a biodegradable matrix of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and investigated the effects of DCD crystal size and loading rates on release rates. RESULTS: Three DCD crystal size fractions (0-106, 106-250 and 250-420 µm) were blended with PHBV at 200, 400, 600 and 800 gkg-1 loadings through extrusion processing and release kinetics were studied in water over 8 weeks. For loadings ≥ 600 g kg-1 , more than 95% release was reached within the first 7 days. By contrast, at 200 g kg-1 loading only 10%, 36% and 57% of the DCD was mobilized after 8 weeks in water for 0 to 106 µm, 106 to 250 µm and 250 to 420 µm crystal size fractions, respectively. CONCLUSION: The lower percolation threshold for this combination of materials lies between 200 and 400 g kg-1 DCD loading. The grind size fraction of DCD significantly affects the quantity of burst release from the surface of the pellet, particularly below the lower percolation threshold. The results presented here are likely translatable to the encapsulation and release of other crystalline materials from hydrophobic polymer matrices used in controlled release formulations, such as fertilizers, herbicides and pesticides. © 2020 Society of Chemical Industry.

Understanding the Mobilization of a Nitrification Inhibitor from Novel Slow Release Pellets, Fabricated through Extrusion Processing with PHBV Biopolymer.

Dicyandiamide (DCD) has been studied as a stabilizer for nitrogen fertilizers for over 50 years. Its efficacy is limited at elevated temperatures, but this could be addressed by encapsulation to delay exposure. Here, poly(3-hydroxybutyrate- co-3-hydroxyvalerate) (PHBV) was investigated as a biodegradable matrix for the encapsulation of DCD. Cylindrical ∼3 mm × 3 mm pellets were fabricated through extrusion processing with 23 wt % DCD. Release kinetics were monitored in water, sand, and both active and γ-irradiated agricultural clay loam soils. Raman maps showed a wide particle size distribution of DCD crystals and indicated that Hitachi's classic moving front theory did not hold for this formulation. The inhibitor release kinetics were mediated by four distinct mechanisms: (i) initial rapid dissolution of surface DCD, (ii) channeling of water through voids and pores in the PHBV matrix, (iii) gradual diffusion of water and DCD through layers of PHBV, and (iv) biodegradation of the PHBV matrix. After ∼6 months, 45-100% release occurred, depending on the release media. PHBV is shown to be an effective, biodegradable matrix for the long-term slow release of nitrification inhibitors.

Plant growth promoting rhizobacteria increase the efficiency of fertilisers while reducing nitrogen loss.

More than half of the applied conventional fertiliser nitrogen (N) in cropping systems can be lost to the environment, resulting in water and air pollution. Farming systems that ensure efficient fertiliser use are crucial to sustain crop productivity without harming the environment. One avenue to achieve this is the use of bio-fertilisers with recognised benefits for plant nutrition and soil heath. Within this area, plant growth promoting rhizobacteria (PGPR) are increasingly applied to enhance plant nutrient acquisition and assimilation. Here, we investigated if PGPR can improve fertiliser performance. We show that the addition of PGPR to soils amended with 50% organic and 50% conventional N fertilisers increased the growth of kikuyu grass (Pennisetum clandestinum), producing yields similar to those obtained using 100% conventional N fertiliser. Encouragingly, this combination also reduced mineral N leaching by 95% relative to the all conventional fertiliser treatment. These findings suggest that using organic and synthetic fertilisers together in the presence of PGPR is a promising approach for sustaining plant growth while reducing potential pollution from inefficient use of conventional N fertilisers.

Mitigating Methane: Emerging Technologies To Combat Climate Change's Second Leading Contributor.

Methane (CH4) is the second greatest contributor to anthropogenic climate change. Emissions have tripled since preindustrial times and continue to rise rapidly, given the fact that the key sources of food production, energy generation and waste management, are inexorably tied to population growth. Until recently, the pursuit of CH4 mitigation approaches has tended to align with opportunities for easy energy recovery through gas capture and flaring. Consequently, effective abatement has been largely restricted to confined high-concentration sources such as landfills and anaerobic digesters, which do not represent a major share of CH4's emission profile. However, in more recent years we have witnessed a quantum leap in the sophistication, diversity and affordability of CH4 mitigation technologies on the back of rapid advances in molecular analytical techniques, developments in material sciences and increasingly efficient engineering processes. Here, we present some of the latest concepts, designs and applications in CH4 mitigation, identifying a number of abatement synergies across multiple industries and sectors. We also propose novel ways to manipulate cutting-edge technology approaches for even more effective mitigation potential. The goal of this review is to stimulate the ongoing quest for and uptake of practicable CH4 mitigation options; supplementing established and proven approaches with immature yet potentially high-impact technologies. There has arguably never been, and if we do not act soon nor will there be, a better opportunity to combat climate change's second most significant greenhouse gas.

Clays Can Decrease Gaseous Nutrient Losses from Soil-Applied Livestock Manures.

Clays could underpin a viable agricultural greenhouse gas (GHG) abatement technology given their affinity for nitrogen and carbon compounds. We provide the first investigation into the efficacy of clays to decrease agricultural nitrogen GHG emissions (i.e., NO and NH). Via laboratory experiments using an automated closed-vessel analysis system, we tested the capacity of two clays (vermiculite and bentonite) to decrease NO and NH emissions and organic carbon losses from livestock manures (beef, pig, poultry, and egg layer) incorporated into an agricultural soil. Clay addition levels varied, with a maximum of 1:1 to manure (dry weight). Cumulative gas emissions were modeled using the biological logistic function, with 15 of 16 treatments successfully fitted ( < 0.05) by this model. When assessing all of the manures together, NH emissions were lower (×2) at the highest clay addition level compared with no clay addition, but this difference was not significant ( = 0.17). Nitrous oxide emissions were significantly lower (×3; < 0.05) at the highest clay addition level compared with no clay addition. When assessing manures individually, we observed generally decreasing trends in NH and NO emissions with increasing clay addition, albeit with widely varying statistical significance between manure types. Most of the treatments also showed strong evidence of increased C retention with increasing clay additions, with up to 10 times more carbon retained in treatments containing clay compared with treatments containing no clay. This preliminary assessment of the efficacy of clays to mitigate agricultural GHG emissions indicates strong promise.

Does manure management affect the latent greenhouse gas emitting potential of livestock manures?

With livestock manures being increasingly sought as alternatives to costly synthetic fertilisers, it is imperative that we understand and manage their associated greenhouse gas (GHG) emissions. Here we provide the first dedicated assessment into how the GHG emitting potential of various manures responds to the different stages of the manure management continuum (e.g., from feed pen surface vs stockpiled). The research is important from the perspective of manure application to agricultural soils. Manures studied included: manure from beef feedpen surfaces and stockpiles; poultry broiler litter (8-week batch); fresh and composted egg layer litter; and fresh and composted piggery litter. Gases assessed were methane (CH4) and nitrous oxide (N2O), the two principal agricultural GHGs. We employed proven protocols to determine the manures' ultimate CH4 producing potential. We also devised a novel incubation experiment to elucidate their N2O emitting potential; a measure for which no established methods exist. We found lower CH4 potentials in manures from later stages in their management sequence compared with earlier stages, but only by a factor of 0.65×. Moreover, for the beef manures this decrease was not significant (P<0.05). Nitrous oxide emission potential was significantly positively (P<0.05) correlated with C/N ratios yet showed no obvious relationship with manure management stage. Indeed, N2O emissions from the composted egg manure were considerably (13×) and significantly (P<0.05) higher than that of the fresh egg manure. Our study demonstrates that manures from all stages of the manure management continuum potentially entail significant GHG risk when applied to arable landscapes. Efforts to harness manure resources need to account for this.

Questioning the accuracy of greenhouse gas accounting from agricultural waste: a case study.

The New Zealand Greenhouse Gas Inventory (the NZ Inventory) uses country-specific data to quantify CH emissions from anaerobic ponds treating dairy farm effluent (315 Gg CO equivalent [CO-e] in 2009). In this study, we used literature data to: (i) evaluate the accuracy of the NZ Inventory's parameters used to quantify these CH emissions; and (ii) determine whether the NZ Inventory's scope is capturing the full spectrum of sources with bio-CH potential entering anaerobic ponds. The research indicated that the current NZ Inventory methodology is underestimating CH emissions from anaerobic ponds across New Zealand by 264 to 603 Gg CO-e annually. Moreover, the NZ Inventory is currently not accounting for (i) manure from supplementary feed pads and stand-off pads (annual CH emissions = 207-330 Gg CO-e); (ii) waste milk (153-280 Gg CO-e); and (iii) supplementary feed waste (90-216 Gg CO-e). Annual CH emissions from anaerobic ponds on dairy farms across New Zealand are thus more likely to be 1029 to 1744 Gg CO-e, indicating that the NZ Inventory is reporting as little as 18% of actual CH emissions produced by this sector. These additional wastes are not accounted for in the methodology prescribed by the Intergovernmental Panel on Climate Change for estimating CH emissions from dairy manure. Consequently, other significant dairying nations will also probably be underestimating their waste CH emissions. Our research highlights that, if governments attempt to include country-specific emission factors in their greenhouse gas inventories, these factors must be based on an assessment of the full spectrum of sources contributing to greenhouse gas emissions within any given sector.

Active slag filters: rapid assessment of phosphorus removal efficiency from effluent as a function of retention time.

There is increasing pressure to upgrade effluent ponds for phosphorus removal. Active slag filters offer a solution, but design information is limited. Hydraulic retention time (HRT) is a key factor in filter design because it controls filter treatment efficiency as well the filter substrate lifespan. This paper reports on a rapid method of continual looping of effluent through a filter column to obtain a relationship between HRT and phosphorus removal efficiency. Phosphorus removal declined logarithmically with respect to retention time. While the mechanisms that yield this relationship involve complex mass transfer and adsorption of phosphorus to Fe oxyhydroxide sites, in general terms, the adsorption rate is proportional to the adsorbate effluent concentration. Waste stabilization pond effluent treated by the slag achieved phosphorus removal efficiencies over 90% at extended HRTs greater than 70 hours, while 80% removal was obtainable in 30 hours. Higher phosphorus removal was achieved for slag treating real effluent compared with synthetic phosphate solution. This can be explained by: (1) different starting phosphorus concentrations in the synthetic phosphate solution and real effluent; and (2) the presence of constituents in real effluent that can enhance phosphorus removal, such as oxidized iron compounds, cations, algae and humic complexes. This new technique, which proved capable of replicating treatment efficiencies obtained from long-term column studies, offers rapid assessment of phosphorus removal efficiency as a function of retention time and thus will enable design engineers to size active filters on the basis of achieving the required phosphorus removal standards.

CH4/CO2 ratios indicate highly efficient methane oxidation by a pumice landfill cover-soil.

Landfills that generate too little biogas for economic energy recovery can potentially offset methane (CH(4)) emissions through biological oxidation by methanotrophic bacteria in cover soils. This study reports on the CH(4) oxidation efficiency of a 10-year old landfill cap comprising a volcanic pumice soil. Surface CH(4) and CO(2) fluxes were measured using field chambers during three sampling intervals over winter and summer. Methane fluxes were temporally and spatially variable (-0.36 to 3044 mgCH(4)m(-2)h(-1)); but were at least 15 times lower than typical literature CH(4) fluxes reported for older landfills in 45 of the 46 chambers tested. Exposure of soil from this landfill cover to variable CH(4) fluxes in laboratory microcosms revealed a very strong correlation between CH(4) oxidation efficiency and CH(4)/CO(2) ratios, confirming the utility of this relationship for approximating CH(4) oxidation efficiency. CH(4)/CO(2) ratios were applied to gas concentrations from the surface flux chambers and indicated a mean CH(4) oxidation efficiency of 72%. To examine CH(4) oxidation with soil depth, we collected 10 soil depth profiles at random locations across the landfill. Seven profiles exhibited CH(4) removal rates of 70-100% at depths <60 cm, supporting the high oxidation rates observed in the chambers. Based on a conservative 70% CH(4) oxidation efficiency occurring at the site, this cover soil is clearly offsetting far greater CH(4) quantities than the 10% default value currently adopted by the IPCC.

Testing a biofilter cover design to mitigate dairy effluent pond methane emissions.

Biofiltration, whereby CH(4) is oxidized by methanotrophic bacteria, is a potentially effective strategy for mitigating CH(4) emissions from anaerobic dairy effluent lagoons/ponds, which typically produce insufficient biogas for energy recovery. This study reports on the effectiveness of a biofilter cover design at oxidizing CH(4) produced by dairy effluent ponds. Three substrates, a volcanic pumice soil, a garden-waste compost, and a mixture of the two, were tested as media for the biofilters. All substrates were suspended as 5 cm covers overlying simulated dairy effluent ponds. Methane fluxes supplied to the filters were commensurate with emission rates from typical dairy effluent ponds. All substrates oxidized more than 95% of the CH(4) influx (13.9 g CH(4) m(-3) h(-1)) after two months and continued to display high oxidation rates for the remaining one month of the trial. The volcanic soil biofilters exhibited the highest oxidation rates (99% removal). When the influx CH(4) dose was doubled for a month, CH(4) removal rates remained >90% for all substrates (maximum = 98%, for the volcanic soil), suggesting that biofilters have a high capacity to respond to increases in CH(4) loads. Nitrous oxide emissions from the biofilters were negligible (maximum = 19.9 mg N(2)O m(-3) h(-1)) compared with CH(4) oxidation rates, particularly from the volcanic soil that had a much lower microbial-N (75 mg kg(-1)) content than the compost-based filters (>240 mg kg(-1)). The high and sustained CH(4) oxidation rates observed in this laboratory study indicate that a biofilter cover design is a potentially efficient method to mitigate CH(4) emissions from dairy effluent ponds. The design should now be tested under field conditions.

Biologically and chemically mediated adsorption and precipitation of phosphorus from wastewater.

Biologically and chemically mediated adsorption and precipitation processes offer a range of approaches for removing phosphorus (P) from agricultural, domestic and industrial effluents. Technologies implemented at full-scale include filtration by adsorbent media, such as steel slag, and recovery of phosphorus as struvite, which has been successfully commercialised as a fertiliser. Other promising technologies under investigation include P removal by polymers and nanomaterials as well as struvite formation by bacteria. There is a need to focus future research on improving the efficiency of P removal by adsorption and precipitation. This can be achieved by techniques such as regenerating filters, polymers and nanomaterials for renewed P removal. Research is also needed to optimise the fertiliser potential of struvite precipitates.

In vitro methane removal by volcanic pumice soil biofilter columns over one year.

Soil methane (CH(4)) biofilters, containing CH(4)-oxidizing bacteria (methanotrophs), are a promising technology for mitigating greenhouse gas emissions. However, little is known about long-term biofilter performance. In this study, volcanic pumice topsoils (0-10 cm) and subsoils (10-50 cm) were tested for their ability to oxidize a range of CH(4) fluxes over 1 yr. The soils were sampled from an 8-yr-old and a 2-yr-old grassed landfill cover and from a nearby undisturbed pasture away from the influence of CH(4) generated by the decomposing refuse. Methane was passed through the soils in laboratory chambers with fluxes ranging from 0.5 g to 24 g CH(4) m(-3) h(-1). All topsoils efficiently oxidized CH(4). The undisturbed pasture topsoil exhibited the highest removal efficiency (24 g CH(4) m(-3) h(-1)), indicating rapid activation of the methanotroph population to the high CH(4) fluxes. The subsoils were less efficient at oxidizing CH(4) than the topsoils, achieving a maximum rate oxidation rate of 7 g CH(4) m(-3) h(-1). The topsoils exhibited higher porosities; moisture contents; surface areas; and total C, N, and available-P concentrations than the subsoils, suggesting that these characteristics strongly influence growth and activity of the CH(4)-oxidizing bacteria. Soil pH values and available-P levels gradually declined during the trial, indicating a need to monitor chemical parameters closely so that adjustments can be made when necessary. However, other key soil physicochemical parameters (moisture, total C, total N) increased over the course of the trial. This study showed that the selected topsoils were capable of continually sustaining high CH(4) removal rates over 1 yr, which is encouraging for the development of biofilters as a low-maintenance greenhouse gas mitigation technology.

Ten-year review of extradural spinal abscesses in a New Zealand tertiary referral centre.

Despite being a well-understood pathology, patients with an extradural spinal abscess (ESA) still experience delays in diagnosis, with associated morbidity and mortality. This 10-year retrospective audit aimed to define the presentation, findings and prognosis of ESA in a New Zealand tertiary referral centre. Forty-two patients were diagnosed and treated between 1 May 1997 and 30 June 2007. The mean age was 55 years, with a male predominance of 1.6:1. Staphylococcus aureus was identified in 67% of patients. On presentation, 27/38 patients with back pain were afebrile and 2/37 patients had a normal C-reactive protein (CRP) level in the first 24 hours. Ten patients were discharged with neurological dysfunction and one died. One reason for the delays in diagnosis and appropriate referral could be the lack of "red flag" symptoms at the time of presentation. Attention needs to be paid to the history and nature of a patient's back pain. We recommend routine CRP and full blood count to help raise clinical suspicion.