Background Phosphorus (P) fertilizer is usually applied in excess of plant requirement and accumulates in soils due to its strong adsorption, rapid precipitation and immobilisation into unavailable ...forms including organic moieties. As soils are complex and diverse chemical, biochemical and biological systems, strategies to access recalcitrant soil P are often inefficient, case specific and inconsistently applicable in different soils. Finding a near-universal or at least widely applicable solution to the inefficiency in agricultural P use by plants is an important unsolved problem that has been under investigation for more than half a century. Scope In this paper we critically review the strategies proposed for the remobilization of recalcitrant soil phosphorus for crops and pastures worldwide. We have additionally performed a meta-analysis of available soil 31P–NMR data to establish the potential agronomic value of different stored P forms in agricultural soils. Conclusions Soil inorganic P stocks accounted on average for 1006 ± 115 kg ha−1 (57 ± 7%), while the monoester P pool accounted for 587 ± 32 kg ha−1 (33 ± 2%), indicating the huge potential for the future agronomic use of the soil legacy P. New impact driven research is needed in order to create solutions for the sustainable management of soil P stocks.
Pregnancy presents significant stresses to a woman's body from the physiological changes to the cardiovascular system, fluid shifts at the time of delivery and the risk of major haemorrhage in the ...peri-partum period. Medications used routinely in daily obstetric practice may have potent vasoactive effects. While most parturients are considered to be healthy and can withstand these significant physiological challenges, as the prevalence of cardiac disease among pregnant women increases it is important to consider the additional impact these medications may have in order to minimise the risk of cardiovascular instability and decompensation. This article will review drugs used in the induction of labour and the management of post-partum haemorrhage, and their relevance for women with cardiac disease.
Although N storage determines early spring growth in trees, the usefulness of autumn N supply remains unclear as N uptake decreases in autumn, but could be restored earlier in spring to compensate ...for low N cycling. We intended here to evaluate the effects of autumn N supply on N uptake, storage and cycling, and spring growth. Four levels of N fertilisation were applied to 1-year-old peach trees, between the end of shoot growth and leaf fall. In spring, N supply was
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N labelled. Organ dry weights and concentrations of
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N,
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N, starch and soluble sugars were evaluated after the first growth flush. Bud development had previously been described in the same trees by Jordan et al. (Trees-Struct Func 23:235–245,
2009
). Fertilisation promoted autumn N uptake, spring N uptake and growth up to a threshold level, since no differences were evidenced between the three highest N treatments. The variability in tree
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N contents was related to the number of phytomers per tree in autumn, i.e. to tree size. In spring, the depletion of the perennial structures was independent of treatment, indicating a complete mobilisation of the N stores. Spring growth was related to the amounts of cycling N, and spring N uptake was in turn proportioned to shoot and fruit growth. The lower N uptake of the N limited trees was not due to a C shortage since these trees displayed the highest starch concentrations. We conclude that a moderate autumn fertilisation improved spring growth and fruit production (Jordan et al. in Trees-Struct Func 23:235–245,
2009
) and that a deficit of N storage could not be compensated for by an increase in spring N uptake.
The establishment of the reference ambient background concentrations (ABCs) and quality reference values (QRVs) for trace metal (TM) concentrations in soils are required for the environmental ...assessment and any implementation of a protective action. This information is lacking for soils of the eastern Mitidja plain, which is an important agricultural production area in Algeria. Data for the aqua regia extractable Cd, Cr, Cu, Fe, Ni, Pb and Zn concentrations from 180 composite topsoil samples taken across the Mitidja plain in a stratified random pattern were statistically analysed. Descriptive statistical methods and linear regression equations were applied to determine the upper limit of the ABCs for the TMs. After removal of outliers, the derived QRVs were: Cd 0.24, Cr 62.1, Cu 99.3, Fe 45 590, Ni 47.7, Pb 33 and Zn 115 mg/kg. Iron is a macro element in the soils, but is included as its concentration can be used to normalise the concentrations of the other elements. The derived QRVs are similar or less than those reported for other regions of the world, apart from Cu, where a wide range (36 to 206 mg/kg) is reported. These reference values can be used to identify areas that may require follow-up surveys or to identify priority sites for decision making.
Background and Aims: Plant acquisition of endogenous forms of soil phosphorus (P) could reduce external P requirements in agricultural systems. This study investigated the interaction of citrate and ...phytase exudation in controlling the accumulation of P and depletion of soil organic P by transgenic Nicotiana tabacum plants. Methods: N. tabacum plant lines including wild-type, vector controls, transgenic plants with single-trait expression of a citrate transporter (A. thaliana frd3) or fungal phytases (phyA: A. niger, P. lycii) and crossed plant lines expressing both traits, were characterized for citrate efflux and phytase exudation. Monocultures and intercropped combinations of single-trait plants were grown in a low available P soil (12 weeks). Plant biomass, shoot P accumulation, rhizosphere soil pH and citrate-extractable-P fractions were determined. Land Equivalent Ratio and complementarity effect was determined in intercropped treatments and multiple-linearregression was used to predict shoot P accumulation based on plant exudation and soil P depletion. Results: Crossed plant lines with co-expression of citrate and phytase accumulated more shoot P than single-trait and intercropped plant treatments. Shoot P accumulation was predicted based on phytase-labile soil P, citrate efflux, and phytase activity (Rsq=0.58, P < .0001). Positive complementarity occurred between intercropped citrate-and phytase-exuding plants, with the greatest gains in shoot P occurring in plant treatments with A. niger phyA expression. Conclusions: We show for the first time that trait synergism associated with the exudation of citrate and phytase by tobacco can be linked to the improved acquisition of P and the depletion of soil organic P.
Most methods used in the identification of counterfeit whisky have focused on the profiling of volatile organic congeners determined by gas chromatography. We tested the use of total reflection x-ray ...fluorescence (TXRF) for trace element analysis of whisky and application of the data as a potential tool in the identification of counterfeit samples. Twenty five whiskies that were produced in different regions of Scotland or were blends, 5 counterfeit whiskies, 1 unmatured grain whisky, and 1 matured grain whisky were analysed for 11 elements (P, S, Cl, K, Ca, Mn, Fe, Cu, Zn, Br and Rb). The effect of cold plasma ashing with oxygen on whisky residues evaporated on the TXRF reflector on the instrument performance was investigated. Cold plasma ashing with oxygen reduced beam scatter and improved the limits of detection but was ultimately deemed unnecessary. The element concentration data for whisky obtained by TXRF (after log transformation) was compared with the values obtained by inductively coupled plasma spectroscopy and showed correlation values (R2) ≥ 0.942 for K, Mn and Cu: ≥ 0.800 for Ca, Fe and Rb; and ≥0.535 for P, S and Zn. The range of concentration values for individual elements was variable and principal components analysis of the elemental concentrations partially differentiated the whiskies by region or type but showed clear separation of the counterfeit samples from the other samples. Using the principal component scores of the elemental concentration data, linear discriminant analysis also distinguished the counterfeits from the other samples.
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•TXRF was applied to the elemental analysis of Scotch whisky and counterfeits for 11 elements.•No sample pre-treatment was required apart from adding Ge as an internal standard.•TXRF limits of detection ranged from 0.1 to 0.001 mg L−1 and compared well with ICP.•Only a small volume of whisky sample was required (10 μL) for the TXRF analysis.•Statistical analysis of the data by PCA and LDA correctly classified the counterfeit whiskies.
The mobility and resupply of inorganic phosphorus (P) from the solid phase were studied in 32 soils from the UK. The combined use of diffusive gradients in thin films (DGT), diffusive equilibration ...in thin films (DET) and the “DGT-induced fluxes in sediments” model (DIFS) were adapted to explore the basic principles of solid-to-solution P desorption kinetics in previously unattainable detail. On average across soil types, the response time (T c) was 3.6 h, the desorption rate constant (k–1) was 0.0046 h–1, and the desorption rate was 4.71 nmol l–1 s–1. While the relative DGT-induced inorganic P flux responses in the first hour is mainly a function of soil water retention and % Corg, at longer times it is a function of the P resupply from the soil solid phase. Desorption rates and resupply from solid phase were fundamentally influenced by P status as reflected by their high correlation with P concentration in FeO strips, Olsen, NaOH–EDTA and water extracts. Soil pH and particle size distribution showed no significant correlation with the evaluated mobility and resupply parameters. The DGT and DET techniques, along with the DIFS model, were considered accurate and practical tools for studying parameters related to soil P desorption kinetics.
We have used an integrated approach to study the mobility of inorganic phosphorus (P) from soil solid phase as well as the microbial biomass P and respiration at increasing doses of citric and oxalic ...acid in two different soils with contrasting agronomic P status. Citric or oxalic acids significantly increased soil solution P concentrations for doses over 2 mmol kg–1. However, low organic acid doses (<2 mmol kg–1) were associated with a steep increase in microbial biomass P, which was not seen for higher doses. In both soils, treatment with the tribasic citric acid led to a greater increase in soil solution P than the dibasic oxalic acid, likely due to the rapid degrading of oxalic acids in soils. After equilibration of soils with citric or oxalic acids, the adsorbed-to-solution distribution coefficient (K d) and desorption rate constants (k –1) decreased whereas an increase in the response time of solution P equilibration (T c) was observed. The extent of this effect was shown to be both soil and organic acid specific. Our results illustrate the critical thresholds of organic acid concentration necessary to mobilize sorbed and precipitated P, bringing new insight on how the exudation of organic acids regulate chemical–microbial soil phosphorus transformations.
Aims Intercropping can improve plant yields and soil phosphorus (P) use efficiency. This study compares inter- and intra-species intercropping, and determines whether P uptake and shoot biomass ...accumulation in intercrops are affected by soil P availability. Methods Four barley cultivars (Hordeum vulgare L.) and three legume species (Trifolium subterreneum, Ornithopus sativus and Medicago truncatula) were selected on the basis of their contrasting root exudation and morphological responses to P deficiency. Monocultures and barley-barley and barley-legume intercrops were grown for 6 weeks in a pot trial at very limiting, slightly limiting and excess available soil P. Aboveground biomass and shoot P were measured. Results Barley-legume intercrops had 10–70% greater P accumulation and 0–40% greater biomass than monocultures, with the greatest gains occurring at or below the sub-critical P requirement for barley. No benefit of barley-barley intercropping was observed. The plant combination had no significant effect on biomass and P uptake observed in intercropped treatments. Conclusions Barley-legume intercropping shows promise for sustainable production systems, especially at low soil P. Gains in biomass and P uptake come from inter- rather than intra-species intercropping, indicating that plant diversity resulted in decreased competition between plants for P.
In the last few decades, the Mitidja plain has undergone economic development which may have altered the concentrations of some trace metals in its soils. Therefore, this study was aimed at ...investigating the concentrations and sources of Cd, Cr, Cu, Fe, Ni, Pb and Zn in 180 composite topsoil samples using a combination of environmental quality indicators and multivariate statistical approaches with a geographic information system (GIS). Based on spatial distribution maps, various hot-spots have been identified. Enrichment factors (EFs) indicated that Cd, Cu, Pb and Zn were from anthropogenic sources, while Ni and Cr were controlled mainly by natural lithogenic source. Multivariate statistical analyses were in agreement, except for Cu which was classified as coming from both anthropogenic and lithogenic sources.
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