Forms of Soil Phosphorus Accumulation in Grassland Soils

Australian soils are generally low in phosphorus (P) by world standards and require applied P to reduce this limitation on plant growth. In grazing systems P is deposited on the soil surface from fertiliser, livestock excretion and senescing pasture. Phosphate occurs in many forms in soils. Because of rising fertiliser prices there is growing interest in assessing and improving the availability of accumulated soil P. The objective of the research described here was to identify and quantify the forms of P in soils under permanent grasslands with a wide range of soil P status

Positive reform of tuna farm diving in South Australia in response to government intervention

© 2001 by Occupational and Environmental MedicineObjectives: Much of the tuna harvested in South Australia since 1990 has involved "farming" techniques requiring the use of divers. From 1993 to 1995, 17 divers from this industry were treated for decompression illness (DCI). In response, the State Government introduced corrective strategies. A decrease in the number of divers presenting for treatment was subsequently recorded. Consequently, the hypothesis was tested that the government intervention resulted in a decrease in the incidence of DCI in the industry and an improved clinical outcome of divers with DCI. Methods: The incidence of treated DCI in tuna farm divers was estimated from the number of divers with DCI treated and the number of dives undertaken extrapolated from a survey of the industry in 1997-8. General health was measured in the tuna farm diving population by a valid and reliable self assessment questionnaire. The outcome of the divers treated for DCI was analysed with a modified clinical severity scoring system. Results: The apparent incidence of treated DCI has decreased in tuna farm divers since the government intervention. The evidence supports a truly decreased incidence rather than underreporting. The general health of the tuna farm divers was skewed towards the asymptomatic end of the range, although health scores indicative of DCI were reported after 1.7% of the dives that did not result in recognised DCI. The clinical outcome of the divers treated since the intervention has improved, possibly because of earlier recognition of the disease and hence less time spent diving while having DCI. Conclusions: The government intervention in the tuna industry in South Australia has resulted in a reduced incidence of DCI in the industry

Trace element distribution and arsenic speciation in toenails as affected by external contamination and evaluation of a cleaning protocol

Open Access via the ACS agreement This research was performed on the XFM beamline at the Australian Synchrotron, part of ANSTO. Special thanks to Prof Dr Rajiv Chowdhury (University of Florida, Miami, USA) for the financial and academic support as scientific manager of the BRAVE study while at the University of Cambridge (Cambridge, UK). We gratefully acknowledge the contributions of all BRAVE study participants, the scientific staff of the collaborating centre icddr,b and the recruitment centre NICVD in Bangladesh. Epidemiological fieldwork in BRAVE has been supported by grants to the coordination centre for BRAVE at the British Heart Foundation (BHF) Cardiovascular Epidemiology Unit (CEU) at the University of Cambridge. The CEU is underpinned by programme grants from the: BHF (RG/13/13/30194; RG/18/13/33946), UK Medical Research Council (MR/L003120/1) and NIHR Cambridge Biomedical Research Centre (BRC-1215-20014; NIHR203312) [*]. *The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care.Peer reviewe

Quantifying the sensitivity of soil microbial communities to silver sulfide nanoparticles using metagenome sequencing

Soils are a sink for sulfidised-silver nanoparticles (Ag₂S-NPs), yet there are limited ecotoxicity data for their effects on microbial communities. Conventional toxicity tests typically target a single test species or function, which does not reflect the broader community response. Using a combination of quantitative PCR, 16S rRNA amplicon sequencing and species sensitivity distribution (SSD) methods, we have developed a new approach to calculate silver-based NP toxicity thresholds (HCx, hazardous concentrations) that are protective of specific members (operational taxonomic units, OTUs) of the soil microbial community. At the HC20 (80% of species protected), soil OTUs were significantly less sensitive to Ag₂S-NPs compared to AgNPs and Ag+ (5.9, 1.4 and 1.4 mg Ag kg-1, respectively). However at more conservative HC values, there were no significant differences. These trends in OTU responses matched with those seen in a specific microbial function (rate of nitrification) and amoA-bacteria gene abundance. This study provides a novel molecularbased framework for quantifying the effect of a toxicant on whole soil microbial communities while still determining sensitive genera/species. Methods and results described here provide a benchmark for microbial community ecotoxicological studies and we recommend that future revisions of Soil Quality Guidelines for AgNPs and other such toxicants consider this approach.Casey L. Doolette, Vadakattu V. S. R. Gupta, Yang Lu, Justin L. Payne, Damien J. Batstone, Jason K. Kirby, Divina A. Navarro, Mike J. McLaughli

Use of 33P to trace in situ the fate of canola below-ground phosphorus, including wheat uptake in two contrasting soils

Our understanding of the contribution of crop root residues to phosphorus (P) cycling is mainly derived from studies using excavated roots re-introduced to soil. This study aims to quantify total below-ground P (BGP) of mature canola in situ and to estimate directly the proportion accessed by subsequent wheat. 33P-Labelled phosphoric acid was fed by stem wick to canola (Brassica napus) grown in sand or loam in pots. Shoots were removed from all plants at maturity. Half of the pots were destructively sampled. After a 3-week fallow, wheat was grown for 5 weeks in the remaining undisturbed pots. At canola maturity, 23–36% of the 33P was partitioned in recovered roots and 34–40% in the soil. More 33P was recovered in the loam than the sand. Within the soil, 6–10%of the fed 33P was present in resin P and 3–5%was in hexanol-released P pools. Ratios of shoot P : BGP(8 : 1 in sand and 15 : 1 in loam) were much narrower than those of shoot P : recovered root P (17 : 1 in sand and 39 : 1 in loam). A greater proportion and amount of the mature canola BG33P was recovered by wheat grown in the loam (26%, 2.6 mg/plant) than in the sand (21%, 1.5 mg/plant). The majority of canolaBG33P remained in the bulk soil. Input of P below-ground by mature canola and subsequent P benefit to wheat was greater in loam than sand. The P from canola below-ground residues contributed up to 20% of P uptake in wheat during the first 5 weeks of growth. Longer term benefits of P from below-ground residues require investigation.Foyjunnessa, C, Ann McNeill, Ashlea Doolette, Sean Mason, and Mike J. McLaughli

Soil phosphorus pools in the detritusphere of plant residues with different C/P ratio - influence of drying and rewetting

Published online: 23 August 2018Little is known about the effect of drying and rewetting (DRW) on phosphorus (P) pools in the detritusphere, the soil adjacent to plant residues. Two plant residues differing in their potential to release P during decomposition were used: mature barley straw, C/ P 255 or young faba bean, C/P 38. Residues were placed between two PVC caps filled with soil at 50% water-holding capacity with open ends covered by fine mesh onto which the residues were placed. The open ends of the two PVC caps were pressed together with residues in between. For the unamended controls, no residues were placed between the meshes. After 2 weeks incubation, the soil was separated from the residues and then either dried and kept dry for 2 weeks followed by rapid rewetting to 50%water-holding capacity (WHC) rewetting (RW) or maintained at 50%ofWHC constantly moist (CM). Bioavailable P pools (readily available P pools: CaCl₂- and anion exchange-P; P bound to soil particles: citrate- and HCl-P; acid phosphomonoesterase- and microbial-P) were measured in dry soil and 1, 7, and 14 days after rewetting. Rewetting of dry soils induced a respiration flush on the first day after which respiration rates declined to those inCM. Compared to the unamended soil, the flush was about 75% higher with barley and more than twofold higher with faba bean. P pools were 3–20-fold higher with faba bean than with barley or in the control. At the end of the dry period, most P pools were higher in dry soil compared to CM. Rewetting had little effect on P pools 1, 7, and 14 days after rewetting compared to CM. To investigate if rewetting induced a short pulse of available P, a second experiment was carried out. As in the first experiment, faba bean detritusphere soil and control were generated and then dried or kept at 50% WHC for 2 weeks. Before rewetting, anion exchange membranes (AEM) were placed in the soil which were removed one, 2 or 4 days after rewetting. The P concentration on the AEMwas more than threefold higher with faba bean than the control. One day after rewetting, the P concentration on the AEM with faba bean was about threefold higher in RWthan in CM, but did not differ between RWand CM in the control. Four days after rewetting, nearly all P pools with faba bean were 10–30% lower in RW than in CM, except citrate-P which was about 5% higher in RW. We conclude that rewetting induces a short pulse of available P if the P pool concentration is high as in the detritusphere of faba bean. If P is removed from the soil (by binding to AEM or uptake by plants), rewetting can induce depletion of P pools compared to CM.Kehinde O. Erinle, Juqi Li, Ashlea Doolette, Petra Marschne

Phosphorus dynamics in a tropical forest soil restored after strip mining

Background and aims We hypothesized that successful early ecosystem and soil development in these P-deficient soil materials will initially depend on effective re-establishment of P storage and cycling through organic matter. This hypothesis was tested in a 26-year chronosequence of seven lightly fertilized, oxidic soil materials restored to eucalypt forest communities after bauxite mining. Methods Total P (Pt) status, Hedley P fractions and partial chemical speciation (NaOH-EDTA extraction and analysed using solution 31P NMR spectroscopy) were determined in the restored soils. Results Concentrations of Pt and most Hedley fractions changed with restoration period, declined with depth and were strongly positively correlated with C and N concentrations. Biological P dominated the Labile and Intermediate P fractions while Long-term P was dominantly inorganic. Organic P concentrations in NaOH-EDTA extracts and their chemical natures were similar in restored and unburned native forest sites. Phosphomonoesters were the dominant class of organic P. Conclusions Surprisingly rapid P accretion and fractional changes occurred over 26 years, largely in the surface soils and closely associated with organic matter status. Alkaline hydrolysis products of phosphodiesters and pyrophosphate indicated the importance of microbial P cycling. The important consequences for long-term ecosystem development and biological diversity require further study

Evaluation of the diffusive gradients in thin-films (DGT) technique for measuring nitrate and ammonium in soil

Rationale. The availability of soil nitrogen for plant uptake can be affected by numerous soil factors such as soil texture, moisture and organic matter content, temperature and microbial activity. Conventional extraction techniques may affect the measurement of plant-available N concentrations following sampling and sample preparation processes, including drying, sieving, homogenising, freezing and thawing. The diffusive gradients in thin-films (DGT) technique can overcome some limitations of the conventional extraction techniques and has been used to successfully estimate the plant-available fractions of nutrients, such as P, K, Zn, Cu and Mn in soils. Therefore, it is important to evaluate the use of DGT for measuring NO₃- and NH₄⁺ in a wide variety of soils and examine the factors that contribute to the plant-availability of these ions in soils. Methodology. The experiment evaluated the ability of the DGT technique to measure NO₃-N and NH₄-N in soils using binding layers containing A520E anion exchange resin or Microlite® PrCH cation exchange resin, respectively. The DGT results were compared to those from conventional KCl extraction. Results. The A520E- and PrCH-DGTs showed good detection limits for NO₃-N (6.90 µg L−¹) and NH₄-N (6.23 µg L−¹) and were able to measure potentially available NO₃-N and NH₄-N in unfertilised soils. The mass of NO₃-N and NH₄-N that accumulated on the DGT device increased linearly across soil concentrations ranging from 5 to 300 mg kg−¹ NO₃-N (depending on soil type) and 5–300 mg kg−¹ NH₄-N; which is equivalent to fertiliser rates of 75–450 kg ha¯¹ N. DGTs were used to measure potentially available NO₃-N and NH₄-N in ten soils with various physical and chemical properties. The DGT results were compared with conventional KCl extraction used to determine soil mineral N. DGT and KCl extraction measured values were significantly correlated with each other for NO₃-N (R² = 0.53; P-value < 0.001), but the relationship between the two measurements was weaker for NH₄-N (R² = 0.20, P-value = 0.045). Discussion. The results suggest that the two methods sample different N pools in the soils, with DGT targeting the NO₃-N and NH₄-N that are available in soil pore water and attached to labile solid phases

Ecological risk assessment of nano-enabled pesticides: a perspective on problem formulation

Plant protection products containing nanomaterials that alter the functionality or risk profile of active ingredients (nano-enabled pesticides) promise many benefits over conventional pesticide products. These benefits may include improved formulation characteristics, easier application, better targeting of pest species, increased efficacy, lower application rates, and enhanced environmental safety. After many years of research and development, nano-enabled pesticides are starting to make their way into the market. The introduction of this technology raises a number of issues for regulators, including how does the ecological risk assessment of nano-enabled pesticide products differ from that of conventional plant protection products? In this paper, a group drawn from regulatory agencies, academia, research, and the agrochemicals industry offers a perspective on relevant considerations pertaining to the problem formulation phase of the ecological risk assessment of nano-enabled pesticides.Glen W. Walker, Rai S. Kookana, Natalie E. Smith, Melanie Kah, Casey L. Doolette, Philip T. Reeves, Wess Lovell, Darren J. Anderson, Terence W. Turney, and Divina A. Navarr