Is land condition a useful indicator of soil organic carbon stock in Australia?

The grazing lands of northern Australia contain a substantial soil organic carbon (SOC) stock due to the large land area. Manipulating SOC stocks through grazing management has been presented as an option to offset national greenhouse gas emissions from agriculture and other industries. However, research into the response of SOC stocks to a range of management activities has variously shown positive, negative or negligible change. This uncertainty in predicting change in SOC stocks represents high project risk for government and industry in relation to SOC sequestration programs. In this paper, we seek to address the uncertainty in SOC stock prediction by assessing relationships between SOC stocks and grazing land condition indicators. We reviewed the literature to identify land condition indicators for analysis and tested relationships between identified land condition indicators and SOC stock using data from a paired-site sampling experiment (10 sites). We subsequently collated SOC stock datasets at two scales (quadrat and paddock) from across northern Australia (329 sites) to compare with the findings of the paired-site sampling experiment with the aim of identifying the land condition indicators that had the strongest relationship with SOC stock. The land condition indicators most closely correlated with SOC stocks across datasets and analysis scales were tree basal area, tree canopy cover, ground cover, pasture biomass and the density of perennial grass tussocks. In combination with soil type, these indicators accounted for up to 42% of the variation in the residuals after climate effects were removed. However, we found that responses often interacted with soil type, adding complexity and increasing the uncertainty associated with predicting SOC stock change at any particular location. We recommend that caution be exercised when considering SOC offset projects in northern Australian grazing lands due to the risk of incorrectly predicting changes in SOC stocks with change in land condition indicators and management activities for a particular paddock or property. Despite the uncertainty for generating SOC sequestration income, undertaking management activities to improve land condition is likely to have desirable complementary benefits such as improving productivity and profitability as well as reducing adverse environmental impact.

Voltammetric determination of isoprenaline in pharmaceutical preparations using a copper(II) hexacyanoferrate(III) modified carbon paste electrode

The electroanalytical determination of isoprenaline in pharmaceutical preparations of a homemade carbon paste electrode modified with copper(II) hexacyanoferrate(III) (CuHCF) was studied by cyclic voltammetry. Several parameters were studied for the optimization of the sensor such as electrode composition, electrolytic solution, pH effect, potential scan rate and interferences in potential. The optimum conditions were found in an electrode composition (in mass) of 15% CuHCF, 60% graphite and 25% mineral oil in 0.5 mol l(-1) acetate buffer solution at pH 6.0. The analytical curve for isoprenaline was linear in the concentration range from 1.96 x 10(-4) to 1.07 x 10(-3) mol l(-1) with a detection limit of 8.0 x 10(-5) mol l(-1). The relative standard deviation was 1.2% for 1.96 x 10(-4) mol l(-1) isoprenaline solution (n=5). The procedure was successfully applied to the determination of isoprenaline in pharmaceutical preparations; the CuHCF modified carbon paste electrode gave comparable results to those results obtained using a UV spectrophotometric method. (C) 2004 Elsevier B.V. All rights reserved.

Preconcentration of polar phenolic compounds from water samples and soil extract by liquid-phase microextraction and determination via liquid chromatography with ultraviolet detection.

2016

Removal of BrO3 − from drinking water samples using newly developed agricultural waste-based activated carbon and its determination by ultra-performance liquid chromatography-mass spectrometry

Activated carbon was prepared from date pits via chemical activation with H3PO4. The effects of activating agent concentration and activation temperature on the yield and surface area were studied. The optimal activated carbon was prepared at 450 °C using 55 % H3PO4. The prepared activated carbon was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric-differential thermal analysis, and Brunauer, Emmett, and Teller (BET) surface area. The prepared date pit-based activated carbon (DAC) was used for the removal of bromate (BrO3 −). The concentration of BrO3 − was determined by ultra-performance liquid chromatography-mass tandem spectrometry (UPLC-MS/MS). The experimental equilibrium data for BrO3 − adsorption onto DAC was well fitted to the Langmuir isotherm model and showed maximum monolayer adsorption capacity of 25.64 mg g−1. The adsorption kinetics of BrO3 − adsorption was very well represented by the pseudo-first-order equation. The analytical application of DAC for the analysis of real water samples was studied with very promising results.

Use of Bioscreen C for growth of Mucor hiemalis in different carbon and nitrogen sources

O sistema automatizado Bioscreen C foi utilizado para o crescimento de quatro linhagens de Mucor hiemalis, isoladas do solo da Estação Ecológica de Juréia-Itatins (EEJI), estado de São Paulo, em meios líquidos com uma única fonte de carbono (2%) ou de nitrogênio (1%), pH 5,0, a 25ºC, e agitação de 150rpm por 5 dias. O meio com somente uma única fonte de nitrogênio foi adicionado com 2% de glicose. As leituras de densidade óptica foram realizadas a 540nm, em intervalos de 2h, por cinco dias. Os resultados foram analisados estatisticamente com o Teste de Friedman (alfa = 5%). Os melhores crescimentos foram obtidos com as linhagens M1, M2 e M3, que atingiram o início da fase log em 60 horas de cultivo. As melhores fontes de carbono variaram de acordo com a linhagem estudada, e extrato de levedura provou ser a melhor fonte de nitrogênio para todas as linhagens. Acetato de sódio inibiu o crescimento das quatro linhagens, sendo a M3 a mais afetada. O uso do sistema automatizado foi muito conveniente para as culturas em meio liquido, sendo rápido e automático, constituindo em uma boa técnica para a determinação das condições ambientais ótimas para crescimento de fungos filamentosos.

Carbon in humic fractions of organic matter in soil treated with organic composts under mango cultivation.

Soil organic matter (SOM) plays a key role in maintaining the productivity of tropical soils, providing energy and substrate for the biological activity and modifying the physical and chemical characteristics that ensure the maintenance of soil quality and the sustainability of ecosystems. This study assessed the medium-term effect (six years) of the application of five organic composts, produced by combining different agro-industrial residues, on accumulation and chemical characteristics of soil organic matter. Treatments were applied in a long-term experiment of organic management of mango (OMM) initiated in 2005 with a randomized block design with four replications. Two external areas, one with conventional mango cultivation (CMM) and the other a fragment of regenerating Caatinga vegetation (RCF), were used as reference areas. Soil samples were collected in the three management systems from the 0.00-0.05, 0.05-0.10, and 0.10-0.20 m layers, and the total organic carbon content and chemical fractions of organic matter were evaluated by determining the C contents of humin and humic and fulvic acids. Organic compost application significantly increased the contents of total C and C in humic substances in the experimental plots, mainly in the surface layer. However, compost 3 (50 % coconut bagasse, 40 % goat manure, 10 % castor bean residues) significantly increased the level of the non-humic fraction, probably due to the higher contents of recalcitrant material in the initial composition. The highest increases from application of the composts were in the humin, followed by the fulvic fraction. Compost application increased the proportion of higher molecular weight components, indicating higher stability of the organic matter.

Carbon Stocks in Compartments of Soil Organic Matter 31 Years after Substitution of Native Cerrado Vegetation by Agroecosystems.

ABSTRACT: Changes in carbon stocks in different compartments of soil organic matter of a clayey Latossolo Vermelho Distrófico (Typic Haplustox), caused by the substitution of native savanna vegetation (cerrado sensu stricto) by agroecosystems, were assessed after 31 years of cultivation. Under native vegetation, a stock of 164.5 Mg ha-1 C was estimated in the 0.00-1.00 m layer. After 31 years of cultivation, these changes in soil C stocks were detected to a depth of 0.60 m. In the case of substitution of cerrado sensu stricto by no-tillage soybean-corn rotation, a reduction of at least 11 % of the soil C pools was observed. However, the adoption of no-tillage as an alternative to tillage with a moldboard plow (conventional system) reduced CO2 emissions by up to 12 %.

Relationships between labile soil organic carbon fractions under different soil management systems.

ABSTRACT: The study of labile carbon fractions (LCF) provides an understanding of the behavior of soil organic matter (SOM) under different soil management systems and cover crops. The aim of this study was to assess the effect of different soil management systems with respect to tillage, cover crop and phosphate fertilization on the amount of the LCF of SOM. Treatments consisted of conventional tillage (CT) and no-tillage (NT) with millet as the cover crop and a no-tillage system with velvet bean at two phosphorus dosages. Soil samples were collected and analyzed for organic carbon (OC), C oxidizable by KMnO4 (C-KMnO4), particulate OC (POC), microbial biomass carbon and light SOM in the 0.0-0.05, 0.05-0.10 and 0.10-0.20 m soil layers. The Carbon Management Index (CMI) was calculated to evaluate the impacts of soil management treatments on the quality of the SOM. The different LCFs are sensitive to different soil management systems, and there are significant correlations between them. C-KMnO4 is considered the best indicator of OC carbon lability. In the soil surface layers, the CT reduced the carbon content in all of the labile fractions of the SOM. The use of phosphorus led to the accumulation of OC and carbon in the different soil fractions regardless of the tillage system or cover crop. The application of phosphate fertilizer improved the ability of the NTsystem to promote soil quality, as assessed by the CMI.

Convergence Of Soil Nitrogen Isotopes Across Global Climate Gradients.

Quantifying global patterns of terrestrial nitrogen (N) cycling is central to predicting future patterns of primary productivity, carbon sequestration, nutrient fluxes to aquatic systems, and climate forcing. With limited direct measures of soil N cycling at the global scale, syntheses of the (15)N:(14)N ratio of soil organic matter across climate gradients provide key insights into understanding global patterns of N cycling. In synthesizing data from over 6000 soil samples, we show strong global relationships among soil N isotopes, mean annual temperature (MAT), mean annual precipitation (MAP), and the concentrations of organic carbon and clay in soil. In both hot ecosystems and dry ecosystems, soil organic matter was more enriched in (15)N than in corresponding cold ecosystems or wet ecosystems. Below a MAT of 9.8°C, soil δ(15)N was invariant with MAT. At the global scale, soil organic C concentrations also declined with increasing MAT and decreasing MAP. After standardizing for variation among mineral soils in soil C and clay concentrations, soil δ(15)N showed no consistent trends across global climate and latitudinal gradients. Our analyses could place new constraints on interpretations of patterns of ecosystem N cycling and global budgets of gaseous N loss.

Effect of silicate fertilization on soil and on palisade grass plants under grazing intensities

Application of calcium silicate (SiCa) as soil acidity corrective was evaluated in a Rhodic Hapludox soil with palisade grass conducted under pasture rotation system with different grazing intensities. Experimental design was complete randomized blocks with four grazing intensities - grazing intensities were imposed by forage supply (50, 100, 150 and 200 kg t-1 of DM per LW) - in experimental plots with four replicates and, in the subplots, with seven doses of calcium silicate combined with lime: 0+0, 2+0, 4+0, 6+0, 2+4, 4+2 and 0+6 t ha-1, respectively. In the soil, it was evaluated the effect of four levels of calcium silicate (0, 2, 4 and 6 t ha-1) at 45, 90, and 365 days at three depths (0-10, 10-20 and 20-40 cm) and at 365 days, it was included one level of lime (6 t ha-1). For determination of leaf chemical composition and silicate content in the soil, four levels of calcium silicate (0, 2, 4 and 6 t ha-1) were evaluated at 45 and 365 days and at 45 days only for leaf silicate, whereas for dry matter production, all corrective treatments applied were evaluated in evaluation seasons. Application of calcium silicate was positive for soil chemical traits related to acidity correction (pH(CaCl2), Ca, Mg, K, H+Al and V), but the limestone promoted better results at 365 days. Leaf mineral contents were not influenced by application of calcium silicate, but there was an increase on silicate contents in leaves and in the soil. Dry matter yield and chemical composition of palisade grass improved with the application of correctives.

Isotopic view of vegetation and carbon and nitrogen cycles in a cerrado ecosystem, southeastern Brazil

Carbon and nitrogen biogeochemical cycles in savannas are strongly regulated by the seasonal distribution of precipitation and pulses of nutrients released during the wetting of the dry soil and are critical to the dynamics of microorganisms and vegetation. The objective of this study was to investigate the spatial and temporal variability of C and N isotope ratios as indicators of the cycling of these elements in a cerrado sensu stricto area, within a protected area in a State Park in the state of São Paulo, Brazil. The foliar δ13C and δ15N values varied from -33.6 to -24.4 ‰ and -2.5 to 4.5 ‰, respectively. The δ13C values showed a consistent relationship with canopy height, revealing the importance of structure of the canopy over the C isotopic signature of the vegetation. Carbon isotopic variations associated with the length of the dry season indicated the importance of recent fixed C to the integrated isotopic signature of the leaf organic C. The studied Cerrado species showed a depleted foliar δ15N, but a wide range of foliar Nitrogen with no difference among canopy heights. However, seasonal variability was observed, with foliar δ15N values being higher in the transition period between dry and rainy seasons. The variation of the foliar C and N isotope ratios presented here was consistent with highly diverse vegetation with high energy available but low availability of water and N.

Lessons from the Terra Preta de Índios of the Amazon region for the utilisation of charcoal for soil amendment

The potential of charcoal and of partially combusted organic waste to mimic the soil organic matter of the Terras Pretas de Índios (Amazonian Dark Earths) from the Amazon Region is discussed. These materials serve as soil conditioners and as sequesterers of carbon in recalcitrant and in reactive forms. Studies carried out by Brazilian and by international groups have contributed to the emergence of an awareness of the compositions and of the uses of these materials. In this contribution we report on chemical studies that are leading to the development of a scientific and technological awareness, and of innovations that will have value in finding novel uses in applications to soil of chars from organic wastes such as those from the biofuel industry, and from metallurgical and various coal plant residues.

Electrochemical Behavior and Determination of Fluconazole

The electrochemical behavior of fluconazole showed an irreversible oxidation process, with the electrochemical - chemical mechanism being highly dependent on the electrode material. Adsorption of reagent at positive applied potential was observed at Pt electrode while preferential adsorption of the oxidation products was observed at Glassy Carbon surfaces. In pH below 7.0, the anodic current process was intensively decreased. At carbon paste electrode, the fluconazole oxidation current, recorded in phosphate buffer solution (pH 8.0), changed linearly with the fluconazole concentration, Ipa = 5.7×10-5 (mA) × 0.052 [Fluconazol] (μg mL-1), in the range of 48.0 to 250.0 μg mL-1. The detection limit obtained was 6.3 μg mL-1.

A biosensor based on immobilization of lactate oxidase in a PB-CTAB film for FIA determination of lactate in beer samples

An amperometric lactate biosensor with lactate oxidase immobilized into a Prussian Blue (PB) modified electrode was fabricated. The advantage of using cetyltrimethylammonium bromide (CTAB) in the electrodeposition step of PB films onto glassy carbon surfaces was confirmed taking into account both the stability and sensitivity of the measurements. The biosensor was used in the development of a FIA amperometric method for the determination of lactate. Under optimal operating conditions (pH = 6.9, E = -0.1 V), the linear response of the method was extended up to 0.28 µmol L-1 lactate with a limit of detection of 0.84 mmol L-1. The repeatability of the method for injections of a 0.28 mmol L-1 lactate solution was 2.2 % (n = 18). The usefulness of the method was demonstrated by determining lactate in beer samples and the results were in good agreement with those obtained by using a reference spectrophotometric enzyme method.

Deep plant-derived carbon storage in Amazonian podzols

Equatorial podzols are soils characterized by thick sandy horizons overlying more clayey horizons. Organic matter produced in the topsoil is transferred in depth through the sandy horizons and accumulate at the transition, at a depth varying from 1 to more than 3 m, forming deep horizons rich in organic matter (Bh horizons). Although they cover great surfaces in the equatorial zone, these soils are still poorly known. Studying podzols from Amazonia, we found out that the deep Bh horizons in poorly drained podzol areas have a thickness higher than 1m and store unexpected amounts of carbon. The average for the studied area was 66.7 +/- 5.8 kgCm(-2) for the deep Bh and 86.8 +/- 7.1 kgCm(-2) for the whole profile. Extrapolating to the podzol areas of the whole Amazonian basin has been possible thanks to digital maps, giving an order of magnitude around 13.6 +/- 1.1 PgC, at least 12.3 PgC higher than previous estimates. This assessment should be refined by additional investigations, not only in Amazonia but in all equatorial areas where podzols have been identified. Because of the lack of knowledge on the quality and behaviour of the podzol organic matter, the question of the feedback between the climate and the equatorial podzol carbon cycle is open.