Spatiotemporal dynamics of soil health in urban agriculture.

There is a paucity of data on the state of urban agriculture soils. In order to develop efficient management practices, it is necessary to understand the seasonal dynamics of the soil health of these systems. This study sampled two community gardens, and one commercial urban agriculture site on a monthly basis over the span of one year. The dynamic analysis examined soil nutritional, chemical and microbial properties. Plant biodiversity was significantly higher in community gardens compared to commercial sites. Analysis of soil nutrients revealed fluctuations of mineral nitrogen with seasonal conditions and consistently high concentrations of plant-available phosphorus. We identified gradually decreasing soil total nitrogen and carbon concentrations throughout the year. Soils were abundant in arbuscular mycorrhizal fungi spores. Soil metabarcoding using 16S and ITS amplicons revealed a seasonal gradient of the microbial diversity and changes after the application of organic fertilizer. Soil-borne potential human pathogens were also detected in the soils. The results of this study provide relevant information about soil management principles in urban agriculture systems. These principles include mulching and the use of nutrient-balanced composts to counteract decreasing carbon pools and the excessive accumulation of phosphorus.

Evaluation of commercial composts and potting mixes and their ability to support arbuscular mycorrhizal fungi with maize (Zea mays) as host plant.

The use of composts and potting mixes in food production systems is a promising way to counteract the effects of soil degradation and allows crop growth in soilless culture systems. Arbuscular mycorrhizal fungi (AMF) are a well-studied group of beneficial plant symbionts that have been shown to provide important ecosystem services. This study analysed the properties of nine commercial Australian potting mixes and composts and investigated whether they support colonization of maize plants with AMF in a plant growth bioassay. Physicochemical analyses showed highly variable properties between the substrates, with some extreme values that limited plant growth. DNA-based analysis revealed the presence of various plant pathogens, which was linked to inhibited plant growth in one substrate. Some substrates did not meet national quality standards, due to the concentrations of plant nutrients, heavy metals, or substrate maturity. Plant growth was mostly limited due to nitrogen immobilization, which required weekly fertilizer applications. Solid state 13C nuclear magnetic resonance spectroscopy gave insight into the decomposition state of the substrates. Plant roots in most substrates were well colonized with AMF (>60% root length), regardless of most substrate properties. Root colonization was negatively affected in only one substrate, likely due to ammonium toxicity. Results of this study show that not all commercial substrates adhered to national quality standards. Potting mixes and composts can support high mycorrhizal root colonization when plant growth is otherwise not limited.

Urban soil health: A city-wide survey of chemical and biological properties of urban agriculture soils.

The integration of urban green spaces into modern city planning is seen as a promising tool to offset the drawbacks of ever-expanding cities. Urban agriculture is a common method to implement such strategies and to increase urban sustainability with a special focus on food security. Due to their location, urban farms are highly influenced by past and present anthropogenic activities which can threaten both soil health and food safety. This study includes 12 urban agriculture sites in the metropolitan area of Adelaide, Australia. It is the first of its kind to focus on soil health in urban agriculture systems with a further emphasis on mycorrhizal fungi. Descriptive information about each site, the biodiversity of the selected plots and soil samples from different depths and locations were collected and analysed for chemical and biological parameters. Seven metals, total and plant-available (Colwell) phosphorus and available nitrogen were measured in soils. A glasshouse bioassay was also conducted to determine the abundance of beneficial arbuscular mycorrhizal fungi in the soils and the change of root colonization after inoculation with the mycorrhizal fungus Rhizophagus irregularis. Results showed a generally high biodiversity of plants that correlated with site activity (commercial or community garden) and which could potentially be used for urban biodiversity conservation. Metal concentrations in soils were below national guidelines levels for all samples, although sites with previous industrial history showed elevated levels when compared to sites without industrial history. The use of raised beds with introduced soils eliminated differences in previous land-use history, thereby providing a good option to support cleaner production. Gardening soils were considered highly fertile, with plant-available (Colwell) P concentrations exceeding recommended levels for most horticultural crops, while soils were adequately supplied with nitrogen. Most plant nutrients were derived from freely available urban waste streams and integrated via composting. Various urban waste streams could be used to counter-act imbalanced soil nutrients. Arbuscular mycorrhizal fungi were present in all sites, indicating that the practiced soil management is sustainable from a microbial perspective. Given their important role in supporting plant nutrition, and potential to reduce the need for external nutrient inputs, they provide an important focal point for achieving clean and sustainable urban food production. The results were incorporated into a framework for the management of urban soil health.

Direct Exports of Phosphorus from Fertilizers Applied to Grazed Pastures.

Since its discovery in 1669, phosphorus (P) in the form of fertilizer has become an essential input for many agroecosystems. By introducing a concentrated P source, fertilizers increase short-term P export potential soon after their application and longer-term export potential by increasing soil fertility (legacy P). The 4R concept was developed to help mitigate P exports from the fertilizers that sustain agricultural productivity. This review investigates the factors affecting P exports soon after the application of mineral fertilizers to pasture-based grazing systems and studies quantifying its potential impact in different systems, with an emphasis on Australasia. Initially, P fertilizers and reactions that might affect their short-term P export potential are reviewed, along with P transport pathways, the forms of P exported from grazing systems, factors affecting P mobilization into water, and studies demonstrating the possible short-term effects of fertilizer application on P exports. Using that foundation, we review studies quantifying the short-term impact of fertilizer application in different regions; they show that under poor management, recently applied fertilizer can contribute a considerable proportion (30-80%) of total farm P exports in drainage, but when fertilizer is well-managed, that figure is expected to be <10%. We then use three model systems of varying hydrology that are common to Australasia to demonstrate the principles for selecting fertilizers that are likely to minimize P exports soon after their application.

Modeling the cadmium balance in Australian agricultural systems in view of potential impacts on food and water quality.

The historical build up and future cadmium (Cd) concentrations in top soils and in crops of four Australian agricultural systems are predicted with a mass balance model, focusing on the period 1900-2100. The systems include a rotation of dryland cereals, a rotation of sugarcane and peanuts/soybean, intensive dairy production and intensive horticulture. The input of Cd to soil is calculated from fertilizer application and atmospheric deposition and also examines options including biosolid and animal manure application in the sugarcane rotation and dryland cereal production systems. Cadmium output from the soil is calculated from leaching to deeper horizons and removal with the harvested crop or with livestock products. Parameter values for all Cd fluxes were based on a number of measurements on Australian soil-plant systems. In the period 1900-2000, soil Cd concentrations were predicted to increase on average between 0.21 mg kg(-1) in dryland cereals, 0.42 mg kg(-1) in intensive agriculture and 0.68 mg kg(-1) in dairy production, which are within the range of measured increases in soils in these systems. Predicted soil concentrations exceed critical soil Cd concentrations, based on food quality criteria for Cd in crops during the simulation period in clay-rich soils under dairy production and intensive horticulture. Predicted dissolved Cd concentrations in soil pore water exceed a ground water quality criterion of 2 µg l(-1) in light textured soils, except for the sugarcane rotation due to large water leaching fluxes. Results suggest that the present fertilizer Cd inputs in Australia are in excess of the long-term critical loads in heavy-textured soils for dryland cereals and that all other systems are at low risk. Calculated critical Cd/P ratios in P fertilizers vary from <50 to >1000 mg Cd kg P(-1) for the different soil, crop and environmental conditions applied.

A difficult conversation? The views and experiences of parents and professionals on the consent process for perinatal postmortem after stillbirth.

OBJECTIVE: To describe the experiences, knowledge and views of both parents and professionals regarding the consent process for perinatal postmortem. DESIGN: Internet-based survey. SETTING: Obstetricians, midwives and perinatal pathologists currently working in the UK. Parents who have experienced a stillbirth in the UK in the previous 10 years. SAMPLE: Obstetricians, midwives and perinatal pathologists registered with their professional bodies. Parents who accessed the Sands website or online forum. METHODS: Online self-completion questionnaire with both fixed-choice and open-ended questions. RESULTS: Responses were analysed from 2256 midwives, 354 obstetricians, 21 perinatal pathologists and 460 parents. The most common reason for parents to request postmortem examination was to find a cause for their baby's death; the prevention of stillbirths in others also ranked highly. Perinatal pathologists possessed greatest knowledge of the procedure and efficacy of postmortem, but were unlikely to meet bereaved parents. The majority of professionals and parents ranked emotional distress and a lengthy wait for results as barriers to consent. The majority of staff ranked workload, negative publicity, religion and cultural issues as important barriers, whereas most parents did not. Almost twice as many parents who declined postmortem examination later regretted their decision compared with those who accepted the offer (34.4 versus 17.4%). CONCLUSION: Emotional, practical and psychosocial issues can act as real or perceived barriers for staff and bereaved parents. Education is required for midwives and obstetricians, to increase their knowledge to ensure accurate counselling, with due regard for the highly individual responses of bereaved parents. The contribution of perinatal pathologists to staff education and parental decision-making would be invaluable.

Transfer functions for solid-solution partitioning of cadmium for Australian soils.

To assess transport and ecotoxicological risks of metals, such as cadmium (Cd) in soils, models are needed for partitioning and speciation. We derived regression-based "partition-relations" based on adsorption and desorption experiments for main Australian soil types. First, batch adsorption experiments were carried out over a realistic range of dissolved Cd concentrations in agricultural soils in Australia. Results showed linear sorption relationships, implying the adequacy of using Kd values to describe partitioning. Desorption measurements were then carried out to assess in-situ Kd values and relate these to soil properties The best transfer functions for solid-solution partitioning were found for Kd values relating total dissolved Cd concentration to total soil Cd concentrations, accounting for the variation in pH, SOM contents and DOC concentrations. Model predictions compared well with measurements of an independent data set, but there was a tendency to underestimate dissolved Cd concentrations of highly polluted soils.

Land application of sewage sludge (biosolids) in Australia: risks to the environment and food crops.

Australia is a large exporter of agricultural products, with producers responsible for a range of quality assurance programs to ensure that food crops are free from various contaminants of detriment to human health. Large volumes of treated sewage sludge (biosolids), although low by world standards, are increasingly being recycled to land, primarily to replace plant nutrients and to improve soil properties; they are used in agriculture, forestry, and composted. The Australian National Biosolids Research Program (NBRP) has linked researchers to a collective goal to investigate nutrients and benchmark safe concentrations of metals nationally using a common methodology, with various other research programs conducted in a number of states specific to regional problems and priorities. The use of biosolids in Australia is strictly regulated by state guidelines, some of which are under review following recent research outcomes. Communication and research between the water industry, regulators and researchers specific to the regulation of biosolids is further enhanced by the Australian and New Zealand Biosolids Partnership (ANZBP). This paper summarises the major issues and constraints related to biosolids use in Australia using specific case examples from Western Australia, a member of the Australian NBRP, and highlights several research projects conducted over the last decade to ensure that biosolids are used beneficially and safely in the environment. Attention is given to research relating to plant nutrient uptake, particularly nitrogen and phosphorus (including that of reduced phosphorus uptake in alum sludge-amended soil); the risk of heavy metal uptake by plants, specifically cadmium, copper and zinc; the risk of pathogen contamination in soil and grain products; change to soil pH (particularly following lime-amended biosolids); and the monitoring of faecal contamination by biosolids in waterbodies using DNA techniques. Examples of products that are currently produced in Western Australia from sewage sludge include mesophilic anaerobically digested and dewatered biosolids cake, lime-amended biosolids, alum sludge and compost.

Effect of water treatment residuals on soil phosphorus, copper and aluminium availability and toxicity.

Water treatment residuals (WTRs) are produced by the treatment of potable water with coagulating agents. Beneficial recycling in agriculture is hampered by the fact that WTRs contain potentially toxic contaminants (e.g. copper and aluminium) and they bind phosphorus strongly. These issues were investigated using a plant bioassay (Lactuca sativa), chemical extractions and an isotopic dilution technique. Two WTRs were applied to an acidic and a neutral pH soil at six rates. Reductions in plant growth in amended soils were due to WTR-induced P deficiency, rather than Al or Cu toxicity. The release of potentially toxic Al from WTRs was found to be mitigated by their alkaline nature and pH buffering capacity. However, acidification of WTRs was shown to release more soluble Al than soil naturally high in Al. Copper availability was relatively low in all treatments. However, the lability of WTR-Cu increased when the WTR was applied to the soil.

Copper lability in soils subjected to intermittent submergence.

Reducing conditions in soils can have significant influences on the availability of nutrient and toxic metals, through their remobilization, their release through reductive dissolution of oxide phases, and from the formation of precipitates. In the literature, contrasting results are reported on the effects of temporary waterlogging conditions on the availability of metals. In the present study, changes in the "labile" or "potentially available" pool of copper (Cu) in soils as a consequence of up to three intermittent soil submergence cycles was investigated using isotopic dilution. The soils (an Oxisol and an Inceprisol) selected were amended in the field with both biosolids-Cu and salt-Cu. Intermittent soil submergence was found to have a significant effect on the lability of Cu in soils, with E(total) values generally increasing in all the treatments with the different submergence cycles, the highest lability of Cu observed in the Cu-salt treatment. The presence of nonexchangeable colloidal forms of Cu, influenced by treatments and submergence cycles, was also reported.

Copper availability in seven Israeli soils incubated with and without biosolids.

Land application is becoming a preferred option for disposal of sewage sludge (biosolids) from wastewater treatment plants. However, it creates potential risks due to the heavy metal contents of these materials, with copper (Cu) being of chief concern. The long-term fate of biosolid metals applied to agricultural soils is not well understood, particularly in the soils of the Middle East. This investigation was conducted to determine whether the availability of Cu changes with time in biosolid-amended and nonamended soils from Israel. Seven soils, typifying the span of properties and formation environments encountered in Israel, were incubated with and without biosolids for 7 yr, and changes in organic carbon (OC) content and labile Cu concentration were determined. Isotopic exchange techniques, using 64Cu, and ion activity measurements, using a Cu2+ ion selective electrode, revealed that the available Cu concentration remained relatively low and stable over the 7-yr incubation. This was despite substantial reductions in OC. This study shows that, with regard to Cu, application of such biosolids to these soils at rates of up to 250 Mg ha(-1) does not pose a threat to the environment in the short to medium term.

Temporal trends of total and potentially available element concentrations in sewage biosolids: a comparison of biosolid surveys conducted 18 years apart.

The application of biosolids to agricultural land is becoming increasingly popular because of the many benefits they can offer in terms of improved soil fertility and productivity, and also because land application offers an economically viable disposal option. However, the heavy metal and nutrient content of biosolids are potential causes for concern due to the possibility of their accumulation in soils to levels that may adversely affect the environment. Therefore, total concentrations of elements in biosolids and the fraction potentially available to organisms must be known in order to accurately gauge the risks and to classify the biosolids. In 1983, deVries conducted a survey to determine the total and available contents of elements in biosolids collected from various treatment plants around Australia. We conducted a similar survey on biosolids collected in 2001, and thus were able to identify temporal trends in biosolid characteristics. The 2001 survey included biosolids from several treatment plants sampled in 1983, thus some direct comparisons were possible, and in four cases, it was possible to examine temporal trends in biosolid characteristics within individual treatment plants. Total element concentrations were determined by aqua regia digestion, and available element concentrations were determined by 0.01 M CaCl(2) extraction. Results showed total concentrations of Cu, Mn, Ni, Na, and Ca changed little over the period examined, however the 2001 median values of Cd, Mg, Pb, and Zn were all reduced by 60% or greater. Median total concentration of K was more than 50% higher, and P 120% higher, in the 2001 survey. Changes in the availability of elements surveyed in 1983 and 2001 were varied for different elements and for different biosolids. Extractable element concentrations (viewed as percentages of total concentrations) of Cu, Cd, and Ni all fell by 50-72% between 1983 and 2001, while K extractability fell by 35%.

The uptake and partitioning of cadmium in two cultivars of potato (Solanum tuberosum L.).

The uptake and distribution of Cd in potatoes over the course of a growing season was investigated in two cultivars of potatoes that differed in tuber Cd concentration. Plants were grown in soil with supplemental Cd. The concentrations of Cd in different tissues varied greatly in the order roots>shoots>> tubers. After the initiation of tuber bulking, shoot growth ceased and the increase in total plant Cd was mostly due to accumulation in the tubers. The constancy of the Cd concentration in shoots suggested that import of Cd via the xylem must be matched by export in the phloem, which implied that Cd must have significant phloem mobility. It was found that the differences in tuber Cd between cultivars Wilwash and Kennebec were not due to differences in total uptake or growth, but to differences in Cd partitioning within the plant. This partitioning was specific to Cd and was not observed for a range of nutrient elements. Most of the differences in tuber Cd concentration between the cultivars could be accounted for by a 3-fold higher retention of Cd in the roots of cv. Wilwash. The involvement of root sequestration, and xylem and phloem pathways in the loading of Cd into tubers is considered.

Background zinc concentrations in soil affect the zinc sensitivity of soil microbial processes--a rationale for a metalloregion approach to risk assessments.

Soil microbial processes are particularly sensitive to Zn, but great difficulty exists in deriving soil standards based on laboratory toxicity tests. Zinc toxicity data for soil microbial processes were collated from the literature, and their variability with soil properties was assessed. Data were screened for quality and reliability, and analysis was based on the highest metal dose at which no adverse effect was found (HNOAED). The HNOAED values were expressed on a pore-water basis and were found to be positively related to background concentrations of Zn in soil, also expressed on a pore-water basis. This suggests that soil microorganisms acclimate to indigenous concentrations of Zn in soil pore water, and this acclimation affects the subsequent response to Zn added as a pollutant. Thus, regions having low background Zn concentrations in soil pore water will be much more sensitive to Zn pollution than others having high background concentrations. A method to account for effects of background Zn on assessments of Zn toxicity is suggested where metalloregions are defined having common sets of abiotic and biotic factors that affect the toxicity of Zn. This approach could markedly improve regional or continental risk assessments for metals in the environment.

Stereoselective trans- and cis-dihydroxylations of 2H-pyranyl and dihydropyridinyl heterocycles synthesized from formal [3 + 3]-cycloaddition reactions of alpha,beta-unsaturated iminium ions with 1,3-dicarbonyl equivalents.

[reaction: see text]We describe here an inherent problem in direct epoxidation of the endocyclic olefin in 2H-pyrans fused to 2-pyrones. Such difficulties led to the development of highly stereoselective trans- and cis-dihydroxylations of these olefinic systems in both 2H-pyrans and dihydropyridines fused to a 2-pyrones or a 2-cyclohexenone. Protocols for the removal of the activated allylic hydroxyl group are also reported.

Determination of metal--EDTA complexes in soil solution and plant xylem by ion chromatography-electrospray mass spectrometry.

An ion chromatography-electrospray mass spectrometry (IC-MS) method was developed to quantify the metal complexes of ethylenediaminetetraacetic acid (EDTA) in soil solution and plant xylem exudate. Suitable separation of the metal-EDTA complexes was achieved on a Dionex AS5 column using 2 mM Na2CO3 as the eluant. However, satisfactory detection by eluant suppressed IC-MS, in either the positive or negative ion detection mode, could not be attained. A new eluant that still attained suitable separation and produced ionic species that could be detected by MS in the negative ion mode was developed. The eluant consisted of 2.5 mM (NH4)2CO3, 9.7 mM NH4OH, and 4% (v/v) methanol and had a pH 9.9. Even though eluant suppressed IC-MS degraded detection limits by a factor of 4 over the nonsuppressed system, using the retention time and not the m/z (mass-to-charge ratio) of the intact chelate for identification, the latter allowed the metal complexes to be detected intact and was optimized for the analysis of environmental samples. The number of metal-EDTA species that could be detected was limited by the eluant used for ion chromatography (i.e. only those complexes that were stable at high pH), with metal-EDTA complexes of Al, Cd, Cu, Co, Mn, Ni, Pb, and Zn being adequately resolved. Iron(III), Ca, MgEDTA, and EDTA itself were not detected. Detection limits for the various complexes ranged from 0.1 to 1 microM.

Trophic barriers to fertilizer Cd bioaccumulation through the food chain: a case study using a plant--insect predator pathway.

The objective of this study was to assess the uptake and subsequent transfer of Cd and Zn from a soil amended with a single application (150 kg P ha(-1)) of triple super phosphate fertilizer to wheat plants, aphids, and a predator and biocontrol agent of aphids, lacewings. The fertilizer amended soil and wheat plants grown on this soil had elevated concentrations of Cd compared to the controls, but similar concentrations of Zn. Aphids feeding on wheat plants on the fertilized soil had between three and seven times the concentrations of Cd and Zn observed in aphids feeding on the control plants. However, the lacewings showed no significant accumulation of Cd or Zn, and no differences in larval performance were recorded. Changes in the availability of Cd and Zn in the soils and the transfer through the plant-insect pathway were monitored using isotope dilution, by labeling the soils with carrier-free (109)Cd and (65)Zn. Decreases in the specific activities for Cd in the plants and aphids were observed for the fertilized soils compared to the controls, suggesting an increase in bioavailable Cd. On the fertilized soils the Cd:Zn ratio of the phloem-feeding aphids (0.008) was significantly less than the host plants (0.025), indicating a reduced relative uptake of Cd and a possible barrier for Cd along the soil--plant--herbivorous insect pathway--reducing uptake by phloem feeders and subsequently their predators.

Root exudates of the hyperaccumulator Thlaspi caerulescens do not enhance metal mobilization.

• To examine whether root exudates of the Zn/Cd hyperaccumulator Thlaspi caerulescens play a role in metal hyperaccumulation, we compared the metal mobilization capacity of root exudates collected from two ecotypes of T. caerulescens, and from the nonaccumulators wheat (Triticum aestivum) and canola (Brassica napus). • Plants were grown hydroponically and three treatments (control, -Fe and -Zn) were later imposed for 2 wk before collection of root exudates. • On a basis of root d. wt, the total soluble organic C in the root exudates of T. caerulescens was similar to that of wheat, and significantly higher than that of canola. In all treatment, the root exudates of T. caerulescens and canola mobilized little Cu and Zn from Cu- or Zn-loaded resins, and little Zn, Cd, Cu or Fe from a contaminated calcareous soil. By contrast, the root exudates of wheat generally mobilized more metals from both resin and soil. In particular, the -Fe treatment, and to a lesser extent the -Zn treatment, elicited large increases in the metal mobilization capacity of the root exudates from wheat. • We conclude that root exudates from T. caerulescens do not significantly enhance mobilization of Zn and Cd, and therefore are not involved in Zn and Cd hyperaccumulation.

Acute dislocation of the trapeziometacarpal joint in a child.

An acute dorsal dislocation of the trapeziometacarpal joint in a child is presented. The mechanisms of injury and controversies of treatment are discussed. The achievement of a stable reduction acutely is emphasized. After healing, joint stability is confirmed by obtaining stress radiographs to identify whether joint subluxation is present before degenerative changes occur.