Subsoil Samples Research Articles

Effect of Verticillium dahliae Soil Inoculum Levels on Spinach Seed Infection.

Verticillium dahliae is a soilborne pathogen and a threat to spinach seed production. The aim of this study was to understand the relation between V. dahliae soil inoculum and infection in harvested seed. Quantitative polymerase chain reaction was used for quantification of the pathogen. Semifield experiments in which spinach was grown in soils with different inoculum levels enabled us to determine a threshold level for V. dahliae DNA of 0.003 ng/g of soil for seed infection to occur. Soils from production fields were sampled in 2013 and 2014 during and before planting, as well as the harvested seed. Seed from plants grown in infested soils were infected with V. dahliae in samples from both the semifield and open-field experiments. Lower levels of pathogen were found in seed from spinach grown in soils with a scattered distribution of V. dahliae (one or two positive of three soil subsamples) than in soils with a uniform distribution of the pathogen (three of three positive soil subsamples). Our results showed that infection of V. dahliae in harvested seed strongly depended on the presence of pathogen inoculum in the soil.

Occurrence and spatial pattern of water repellency in a beech forest subsoil

Abstract Most recent studies on soil water repellency (WR) were limited to the humous topsoil or to shallow subsoil layers slightly below the main root zone to approximately 0.5 m depth. Hence, the main objective of the present study was to investigate the wettability pattern of a forest soil including the deeper subsoil. The selected site was a 100 years old beech forest on a well-drained sandy Cambisol in northern Germany which showed moderate to partly extended acidification. Results obtained from three sampling transects (3 m length, 2 m depth; sampling grid 8 × 8 samples per transect; minimum distance of sampling locations to nearest tree about 0.5 m) show that contact angles (CA) were always in the subcritical WR range (0° < CA < 90°). Significant impact of the tree distance on WR was not observed for any of the transects. A prominent feature of two transects was the minimum WR level (CA < 10°) for samples with soil organic carbon (SOC) contents around 0.25–0.4%. For the topsoils it was observed that CA increased with SOC content from that minimum to a maximum CA of 60–75° for transects 1 and 2 with mean pH values < 3.5. For transect 3 with slightly higher average pH close to 4.0, average CA of samples were always < 10° and showed no trend to increase with increasing SOC content or other soil parameters like N content or C/N ratio. Subsoil samples, however, behave differently with respect to SOC: for these samples, generally low in SOC, the CA increase with decreasing SOC occurred at all transects for approximately 50% of the samples but did not show any clear tendencies with respect to further parameters like texture, pH or N content. We conclude that the SOC content is the most prominent parameter determining wettability, either positively correlated with WR for topsoils or negatively correlated for subsoil samples very low in SOC. We finally conclude for moderately acid beech forest stands that emerging WR starts in the A horizon after reaching a pH lower than 3.5, whereas subsoil WR might appear already at higher pH values. Even SOC contents of ~0.01–0.02% turned out to be very effective in increasing the CA up to 70°, which points out clearly the importance of small amounts of soil organic matter in affecting subsoil wettability. With respect to site hydrology we conclude that ongoing acidification as well as predicted higher frequencies of extended droughts due to climate change will promote the occurrence of WR with corresponding implications for site and catchment hydrology.

Effects of Integrated Soil Amelioration Techniques to Mature Newly Established Research Fields

The Rural Development Administration moved to Jeonju for the balanced development of the land. This situation required establishment of new research fields with soils appropriate to cultivation. We applied a variety of amelioration techniques to mature soils of new research fields of the National Institute of Agricultural Science (NAS) and evaluated effects of the integrated amelioration techniques. The schedule of amelioration was following: 1) location of research fields was determined, 2) surface and subsoil samples were collected separately, 3) after aligning the top level of research fields, subsoil and surface soil were re-established with soil amendment, 4) the green manure crops were grown four seasons to improve the uniformity and increase the organic content of the research field, and 5) drainage canal and/or underdrainage were applied to poorly drained fields. The last green manure crop was rape in RDA fields and green barley in NAS fields. The average height, fresh weight, and dry matter weight of rape in good condition were 123 cm, <TEX>$3,938kg\;10a^{-1}$</TEX>, and <TEX>$651kg\;10a^{-1}$</TEX>, respectively. The height, fresh weight, and dry matter of green barley, on average, were 97 cm, <TEX>$3,013kg\;10a^{-1}$</TEX>, and <TEX>$1,004kg\;10a^{-1}$</TEX>, respectively. In the chemical properties of paddy field, pH and levels of silicate, calcium, magnesium, and potassium were in appropriate range but organic matter content of <TEX>$16g\;kg^{-1}$</TEX> was less than the optimum level. In the chemical properties of upland field, pH and levels of phosphorus, calcium, magnesium, and potassium were appropriate range but organic matter content of <TEX>$12g\;kg^{-1}$</TEX> was less than the optimum range. Evaluation of well-adapted soil was performed. The field in RDA was classified into the superior class with points ranging from 90 to 95 by the field evaluation test. The fields in NAS were mainly evaluated as the superior class with points greater than 85. However, some fields in NAS remained low quality with scores between 80 and 83. Further soil amelioration practices were suggested to fields with low soil quality.

Characterization and fingerprinting of soil and groundwater contamination sources around a fuel distribution station in Galicia (NW Spain).

Soil and groundwater contamination around a fuel distribution station in Tomiño (NW Spain) was evaluated. For this purpose, top and subsoil (up to 6.4 m) and groundwater were sampled around the station, approximately in a 60-m radius. Samples were analysed by HS-SPME-GC-MS to identify and quantify volatile fuel organic compounds (VFOC) (MTBE, ETBE and BTEX) and diesel range organics (DRO). Analysis and fingerprinting data suggested that the contamination of soil and groundwater was provoked by a fuel leak from underground storage tanks. This was reflected by hydrocarbon indices and principal component analysis, which discriminated a direct source of contamination of the subsoil samples around the station. The contaminants probably migrated from tank nearby soils to surrounding soils and leached to groundwater, following a SW direction. Irrigation with contaminated groundwater provoked a severe contamination of topsoils, which were enriched with the lightest components of gasoline and diesel. Fingerprinting also revealed the continuity of the leak, reflected by the presence of volatiles in some samples, which principally appeared in fresh leaks. MTBE was detected in a very high concentration in groundwater samples (up to 690 μg L(-1)), but it was not detected in fresh gasoline. This also evidenced an old source of contamination, probably starting in the mid-1990s, when the use of MTBE in gasoline was regulated.

Effectiveness of cracker dust as a capping material for Pb-rich soil in the mining town of Broken Hill, Australia

Lead (Pb)-poor ‘cracker dust’, commonly used in kerb and gutter construction, has been installed on top of Pb-rich soil surfaces in Broken Hill over the last few decades, with the aim of reducing the risk of human exposure to Pb particulates. In this study, topsoil (0–0.1m) and subsoil (0.3–0.5m) samples were collected along rays spanning all parts of the Broken Hill urban area to investigate the effectiveness of remediation with cracker dust. Total Pb concentrations in the fine earth fraction (<2mm) of topsoil and subsoil samples and the dust-sized fraction (<100μm) of topsoil samples were measured. Undisturbed subsoil Pb concentrations are high near the ‘Line of Lode’ (LoL) orebody, especially on its southern flank, but are similar to background Pb concentrations at locations more than 0.8km from the LoL. Topsoil Pb concentrations at locations near the LoL are very high, but tend to decrease rapidly with increasing distance from the LoL. At most sampled locations the topsoil is significantly enriched in Pb relative to the subsoil, while Pb concentrations in the dust-sized fraction of topsoils are generally twice as high as those in the fine earth fraction of topsoils. Notably, where cracker dust has been applied, most topsoil Pb concentrations are significantly lower, indicating that remediation with cracker dust has been generally effective. Although contemporary dust deposits in Broken Hill can be very rich in Pb, the relatively small amounts of dust deposited ensure that Pb accretion from fugitive dust deposition is a very gradual process; undisturbed cracker dust should have a ‘clean lifespan’ of at least 100years. However, a small number of cracker dusted sites are found to have Pb-enriched surfaces, suggesting that the efficacy of cracker dust is curtailed where fluvial transport of Pb-rich sediment and/or mixing of the applied cracker dust with the underlying Pb-rich soil occurs.

Using cesium-137 to quantify sediment source contribution and uncertainty in a small watershed

Knowledge of sediment provenance is critical for precision conservation planning and calibration of soil erosion models. The objectives are to evaluate the ability of 137Cs to apportion sediment source contributions, quantify uncertainty of the estimates, and estimate desirable sample numbers. We collected 50 surface soil samples from overland in a watershed (15.6km2), 28 subsoil samples from gully bank, and 43 sediment samples in channels. The 137Cs activity was measured by γ spectrometry. Proportion means were calculated by solving a linear mixing model. Uncertainty was estimated by the first-order approximation and Monte Carlo (MC) simulation. The 137Cs tracer was conservative in the fraction of <63μm. The 137Cs activities differed between sources in the whole watershed at P=0.05. The mean proportions of the <63μm fraction (relative error) predicted for the watershed using the mixing model were 0.42 (35%) for the overland source and 0.58 (25%) for the gully source, with a 95% confidence interval of ±0.145 for both. Overland source contributed most uncertainty to the proportion estimates, followed by sediment, with minimum from gully. The MC simulation predicted the same mean proportions, but with relative errors being <3% for both. Compared with the first-order approximation, MC underestimated uncertainty of the means due to the large sample number used in simulation. In general, 30 to 50 samples are needed for each source and sediment to generate reliable estimates using 137Cs. Estimated source proportions of the fine sediment may be converted to proportional contributions of total soil erosion by adjusting by particle sizes and sediment delivery ratio. No adjustment or weighting should be made directly to the mixing model unless conservativeness of the tracer is violated.

Changes in the properties of Fijian Oxisols over 30 years of sugarcane cultivation

Sugarcane production plateaued in Fiji at ~4 million tonnes annually (average ~55 t/ha) during the latter part of the 1980s but, in recent years, despite the continuing release of high yielding varieties, the total production has decreased to under 3 million tonnes (average ~45 t/ha). This study was initiated to study the changes in the properties of Oxisols following sugarcane cultivation to ascertain whether yield declines were due to degradation of soil biophysical and chemical properties. The study lasted from 1978 (when the soils were first cleared for agriculture) to 2009. Soil (0–15, 30–40 and 70–80 cm) properties including pH, organic carbon, cation exchange capacity, water retention, bulk density, phosphate retention and exchangeable bases were monitored. The observed topsoil changes could generally be related to changes in organic matter and associated ion exchange properties. The major changes occurred in the first three years after clearing, but some changes continued for many years. Subsoil samples (30–40 cm) showed an increase in organic carbon after cane cultivation, probably due to soil mixing during land preparation, organic matter movement during cropping and decay of sugarcane roots. At 70–80 cm, small but significant increases in organic carbon were observed along with small decreases in pH. Overall, these changes indicate that careful management of topsoils is essential for maintaining soil fertility and hence sugarcane productivity on these highly weathered soils.

Fertilizer effects on phosphorus fractions and organic matter in Andisols

Andisols are characterized by a high phosphorus (P) fixation capacity, which is a limiting factor for plant production. Continuous application of P fertilizer may result in an accumulation of P associated with soil organic matter (SOM), which further acts to reduce the availability of the added P. The objectives of this study were (1) to evaluate the impact of P fertilizer inputs on the quantities and chemical forms of P, and (2) to investigate relationships between P forms SOM and land use. Topsoil (0-20 cm) and subsoil (20-40 cm) samples were taken from two Andisols series under grassland and arable cropping. Soil P forms were determined using sequential fractionation, while SOM analysis involved a combination of 13C nuclear magnetic resonance (NMR) spectroscopy and pyrolysis-GC-mass spectrometry. Fertilization increased total P, total organic P, organic carbon, and inorganic P fractions, mainly in arable soils. Labile P was higher in grassland (3% of total P) than in arable soils (1% of total P). A clear effect of fertilization was observed on organic matter compounds measured by pyrolysis in both soil depths. Interestingly, the polysaccharide-derived compounds increased in fertilized soils and lipid-derived compounds decreased. Thus fertilization principally affected labile P and labile SOM forms, whereas recalcitrant forms of P and SOM remained unchanged.

Impact of Repeated Applications of Metalaxyl on Its Dissipation and Microbial Community in Soil

Metalaxyl, an important phenylamide fungicide, is widely used for controlling fungal diseases caused by pathogens of the orders Peronosporales and Pythiales. Under laboratory conditions, metalaxyl was applied to soil samples at the recommended field rate (1×FR) and double of recommended field rate (2×FR) for two and three times. Soil subsamples were taken at 0, 1, 3, 7, 14, 28, and 45 days after the last application of metalaxyl for determination of metalaxyl residues and 7, 14, 28, and 56 days for enumeration of cultivable microorganisms and DGGE profile of soil microbial community. Soil incubation experiments revealed that metalaxyl was degraded faster in the third application than in the second application of the fungicide, half-lives of metalaxyl decreasing from 16.2 to 9.9 days for recommended field rate and 22.1 to 20.0 days for double of recommended field rate. Soil bacterial and fungal populations decreased in the first 14 days and then recovered to the control levels; population of actinomycetes did not alter in the first 28 days but increased at the end of the experiment after the second application. However, after the third treatment, temporary increase in soil bacteria population, nonsignificant inhibition effect on fungal population, and obvious stimulation effect on actinomycetes number were observed. DGGE results showed that successive inputs of metalaxyl altered the bacterial community structure. There were differences in the persistence and effects of metalaxyl on microbial community between the second and the third metalaxyl treatments.

What do yellowish-brown soils and stone layers tell us about Late Quaternary landscape evolution and soil development in the humid tropics? A field study in the Serra dos Órgãos, Southeast Brazil

The occurrence, spatial distribution and properties of yellowish-brown soils and stone layers allow deriving conclusions about landscape evolution and soil development in the humid tropics. In this study, standard soil profiles and saprolite and subsoil samples along an altitudinal gradient from the high mountain ranges (~1500m.a.s.l.) to the lowlands (~8m.a.s.l.) in the Serra dos Órgãos mountain range in the Brazilian state of Rio de Janeiro are analyzed. Field mapping techniques and laboratory methods are used to analyze the samples and reconstruct Late Quaternary landscape and soil development processes.It is suggested that the formation of stone layers is polygenetic with dissolution processes (geogenic), bioturbation (pedogenic), and slope processes including coverage of terrace gravels (geomorphic) as possible mechanisms. Yellowing of the upper soil horizons is assumed to be the result of (bio)chemical processes (xanthization, chelation), which took – and take – place in periods of wet climate conditions and closed forest cover in the Late Quaternary. It can be distinguished between pre-colonial and modern yellowish-brown colluvial deposits with or without stone layer(s). It is suggested that the deposition of pre-colonial colluvial soils primarily took place in dryer periods and forest retreat during the Late Pleistocene and Holocene. However, it is proposed that the model of cyclic changes between geomorphic activity with colluviation on the one hand and stability and pedogenesis on the other hand need to be further differentiated due to small-scale temporal and spatial climatic changes and sensitive vegetation responses to these fluctuations. Moreover, it is suggested that due to the very steep relief and intense rainfall in the central mountain ranges of the Serra dos Órgãos, accelerated displacement of soil material by landslides and mudslides took also place under closed forest cover in the late Holocene. Modern colluvial deposits have originated from deforestation and land use intensification processes within the last 300years. They cover wide parts of the lower slopes, foothills, and depressions and indicate massive erosion and deposition processes since the European colonization.

Bioaccessibility of lead in urban soil of Broken Hill, Australia: A study based on in vitro digestion and the IEUBK model

This study was conducted to investigate lead (Pb) bioaccessibility in urban soil and to assess health risk to children in the city of Broken Hill, Australia, which was established around one of the world's largest lead–zinc–silver mines. Fifty-three topsoil (0–0.1m) and 50 subsoil (0.3–0.5m) samples were collected from earthen footpaths, nature strips, parks or vacant land throughout the urban area. The soil samples were analysed for total Pb concentration, Pb bioaccessibility and Pb mineral phases, together with important soil physicochemical properties known to influence Pb bioaccessibility. Lead bioaccessibility ranged from 24% to 89% in topsoil and from 16% to 100% in subsoil, exhibiting a generally decreasing pattern with increasing distance from the orebody. Lead bioaccessibility was strongly positively related to total Pb concentration in both the topsoil and subsoil. In subsoil, a moderate negative correlation existed between Pb bioaccessibility and soil pH, while a moderate positive correlation existed between Pb bioaccessibility and soil organic matter (OM) content. In contrast, only a weak positive correlation existed between Pb bioaccessibility and OM content in topsoil. The presence of different Pb mineral phases also appeared to have caused variation in soil Pb bioaccessibility, with galena (PbS)-rich samples tending to exhibit lower Pb bioaccessibility. The prediction of blood lead (PbB) levels in Broken Hill children aged 1–4years using the IEUBK model well matched the measured data from a recent PbB screening, suggesting a high risk of childhood chronic low-level Pb exposure (PbB levels >5μg/dL) in Broken Hill, especially in the vicinity of the orebody. Future Pb abatement programs in Broken Hill should utilise the IEUBK model to establish target soil Pb values in an effort to achieve particular child PbB outcomes.

Distribution of terbuthylazine and atrazine residues in crop-cultivated soil: The effect of herbicide application rate on herbicide persistence

Field experiments were carried out to compare the effect of herbicide application rate on the distribution and persistence of atrazine (ATR), terbuthylazine (TBA), and their dealkylated degradation products in two conventionally cultivated cornfield soils: a silt loam soil and a silty clay loam soil, both typical for the crop-producing area of continental Croatia. Herbicides were applied pre-emergence at the registered (R) (1.0–1.5kgha−1), double-registered (2R), and triple-registered (3R) rates. Topsoil (0–30cm) and subsoil (30–60cm) samples were collected periodically during a crop rotation cycle of 17months. Soil microcosm experiments were performed under controlled conditions to investigate the influence of the herbicide application rate on their biodegradation in herbicide-treated cornfield topsoils. The herbicide half-lives (DT50) calculated by using monophasic and biphasic first-order kinetics models were compared. The herbicide sorption intensity in the studied soils was evaluated in terms of the Freundlich sorption isotherm. Under field conditions, TBA was retained within the first 60cm of both agricultural soils at least twice as long as ATR. While ATR residues persisted in soil only until corn harvest (5months), the residues of TBA and its N-deethylated degradation product were still measurable at the end of the crop rotation cycle (17months). The persistence of both herbicides was higher in soil with higher herbicide sorption intensity. ATR and TBA application rates higher than registered generally did not significantly influence the herbicide biodegradation rates or dissipation from the topsoil layers. The enhanced application rate slightly decreased the TBA persistence only in soil exhibiting a rather slow biodegradation. A temperature-leaching potential index for ATR and TBA applied at R rate showed the same leachability class for both herbicides. The leachability class of TBA could be higher than that of ATR in soil with moderate TBA persistence (DT50=30–100days). From an environmental perspective, TBA could pose a similar risk for groundwaters as ATR.

Funcionalidad de hongos micorrízicos arbusculares en tres comunidades vegetales de la Reserva Florística Manejada de San Ubaldo-Sabanalamar, Cuba

&lt;p&gt;Despite the ubiquity and importance of indigenous arbuscular mycorrhizal fungi (AMF) for plant ecosystems; functioning of indigenus mycorrhizal symbiosis (IMS) and related environmental factors at coastal Caribbean ecosystems remains still scarce. In order to determine functionality of IMS under contrasting land uses and wet seasons from Cuba, the influence of the water stress on some AMF functionality parameters from a semi-natural savannah (NS), a recovered savannah (RS) and an agro-ecosystem (AG) from the Managed Floristic Reserve San Ubaldo-Sabanalamar, Pinar del Rio, Cuba were assessed during two-years. Soil and root samples were collected in April and October, during the dry and wet seasons, respectively, in 2008 and 2010. Four plots in each ecosystem were selected, and five soil sub-samples were randomly collected, bulked, mixed homogeneously and used as the composite sample per plot. The host plant root biomass, arbuscular mycorrhizal colonization of the host plant, density of the intraradical and extraradical AMF mycelia, fungal endophyte biomass and AMF spore density were assessed. The host plant root biomass increased in the NS environment during the dry season, and approximately 12.85g root/dm&lt;sup&gt;3&lt;/sup&gt; dry soil was recorded. The colonization scores were significantly higher in all environments during the wet season of the second year, with means ranging from 79% to 89%. The extraradical mycelia were significantly more abundant in the dry season of the second year in all environments, with a maximum of 279mg/dm&lt;sup&gt;3&lt;/sup&gt; in the RS ecosystem. The density of AMF spores was highest in the dry season of the second year for the three studied ecosystems. The RS ecosystem hosted 5 670 spores/100g dry soil. In general, the influence of rainfall seasonality on the function of AMF was stronger than the influence of ecosystem management. The root biomass and extraradical mycelia were high in the dry seasons, suggesting strategies to increase the volume of soil for the mutual benefit of the symbionts. The increase in spore density during the dry seasons appears as an adaptation allowing AMF to survive period of water shortage. This study improves our understanding of the adaptative responses of arbuscular mycorrhizal symbiosis to seasonal variations in soil water availability. &lt;/p&gt;

English

This study examined the differences in the nutrient concentration of the parent material of teak plantations under basement and sedimentary rocks in south western Nigeria. Systematic line transect was employed to establish 18 plots (30 m x 30 m), each in Ilaro (sedimentary rock) and Olokemeji (basement complex rock) plantations which were 37, 40 and 42 years old while twelve rock samples each from 3 quadrants each of 30 m2 were selected for rock nutrient analysis. Topsoil (0-15 cm) and subsoil (15-30 cm) samples, above-ground plant parts (leaf, bark, stem, twig and branch) and biomass parameters (bole height, girth, total height and crown diameter) were collected. The soil samples were analyzed for soil physicochemical and micronutrients while plant parts were analyzed for nutrient contents (nitrogen, phosphorous, potassium, calcium and magnesium) using standard procedures. Pearson’s correlation and regression analysis were used to establish the type and level of association between soil properties and vegetation parameters respectively at p<0.05. The result indicates that there is no significant difference between the various minerals found in the rocks of the two locations. Secondary test indicate that there is significant difference among the three horizons A, B and C on the mean concentration of phosphorus and iron with p = 0.008<0.05 and p = 0.046 < 0.05 respectively. The multiple comparisons revealed that there is no statistical significant difference in phosphorous concentration between horizons A and B horizon but that there is a statistical significant difference between horizon A & C and B & C with p = 0.005< 0.05 for all. Key words: Bedrock geology, parent rock materials, physical properties, physico-chemical properties, soil nutrients.

The Chemophytostabilisation Process of Heavy Metal Polluted Soil.

Industrial areas are characterised by soil degradation processes that are related primarily to the deposition of heavy metals. Areas contaminated with metals are a serious source of risk due to secondary pollutant emissions and metal leaching and migration in the soil profile and into the groundwater. Consequently, the optimal solution for these areas is to apply methods of remediation that create conditions for the restoration of plant cover and ensure the protection of groundwater against pollution. Remediation activities that are applied to large-scale areas contaminated with heavy metals should mainly focus on decreasing the degree of metal mobility in the soil profile and metal bioavailability to levels that are not phytotoxic. Chemophytostabilisation is a process in which soil amendments and plants are used to immobilise metals. The main objective of this research was to investigate the effects of different doses of organic amendments (after aerobic sewage sludge digestion in the food industry) and inorganic amendments (lime, superphosphate, and potassium phosphate) on changes in the metals fractions in soils contaminated with Cd, Pb and Zn during phytostabilisation. In this study, the contaminated soil was amended with sewage sludge and inorganic amendments and seeded with grass (tall fescue) to increase the degree of immobilisation of the studied metals. The contaminated soil was collected from the area surrounding a zinc smelter in the Silesia region of Poland (pH 5.5, Cd 12 mg kg-1, Pb 1100 mg kg-1, Zn 700 mg kg-1). A plant growth experiment was conducted in a growth chamber for 5 months. Before and after plant growth, soil subsamples were subjected to chemical and physical analyses. To determine the fractions of the elements, a sequential extraction method was used according to Zeien and Brümmer. Research confirmed that the most important impacts on the Zn, Cd and Pb fractions included the combined application of sewage sludge from the food industry and the addition of lime and potassium phosphate. Certain doses of inorganic additives decreased the easily exchangeable fraction from 50% to 1%. The addition of sewage sludge caused a decrease in fraction I for Cd and Pb. In combination with the use of inorganic additives, a mobile fraction was not detected and an easily mobilisable fraction was reduced by half. For certain combinations of metals, the concentrations were detected up to a few percent. The application of sewage sludge resulted in a slight decrease in a mobile (water soluble and easily exchangeable metals) fraction of Zn, but when inorganic additives were applied, this fraction was not detected. The highest degree of immobilisation of the tested heavy metals relative to the control was achieved when using both sewage sludge and inorganic additives at an experimentally determined dose. The sequential extraction results confirmed this result. In addition, the results proved that the use of the phytostabilisation process on contaminated soils should be supported.

Laboratory-based evaluation of optical performance for a new soil penetrometer visible and near-infrared (VisNIR) foreoptic

In situ visible and near infrared (VisNIR) spectroscopy has been gaining interest as a proximal soil sensing technique to rapidly and inexpensively measure soil properties. For this study, our goal was to design a VisNIR soil penetrometer foreoptic that matched the optical performance of a commercial ASD (Analytical Spectral Devices Inc., Boulder, CO, USA) foreoptic and was compatible with any spectrometer having a fiber optic input (e.g. commonly used ASD field spectrometers). Space available for penetrometer optics was constrained by a several practical design requirements: (a) ability to collect in situ soil VisNIR reflectance and insertion force simultaneously; (b) thick probe walls strong enough for insertion into dry soil with high clay content; and (c) a narrow enough cross-sectional diameter for insertion using a standard soil coring hydraulic push system. In this paper, we evaluate the optical and chemometric performance of our design relative to a commercial ASD foreoptic under controlled conditions in a laboratory setting, in order to isolate the optical performance of the probe from complications associated with in situ use. Both the VisNIR penetrometer and ASD Contact Probe, attached to an ASD AgriSpec spectrometer in the lab, were used to interrogate 389 milled and pressed surface and subsoil samples taken from two US continent-scale transects. The reflectance spectra obtained from these two foreoptics were highly correlated (r>0.95 for most wavelengths) and the 1st derivatives of the spectra were well correlated for all but the detector splice points (r>0.9 for most wavelengths). Partial least squares regression (PLSR) was used to calibrate and validate VisNIR models predicting soil organic carbon content for both foreoptics. Using reflectance data, our VisNIR penetrometer yielded quantitative SOC predictions with standard error of prediction (SEP=0.19log[gkg−1]) and ratio of prediction to determination (RPD=2.34) highly similar to the ASD contact probe (SEP=0.18 and RPD=2.45). Regression coefficients of PLS calibration models from both foreoptic were comparable and highly correlated (r=0.91). These results suggest that our penetrometer foreoptic provides VisNIR reflectance spectra comparable to a widely-used commercial foreoptic. In future work, we deploy this penetrometer in the field and evaluate the performance of this foreoptic where soil heterogeneity, smearing and moisture can impact the quality of VisNIR spectra.

Decoding potential effects of climate and vegetation change on mineral weathering in alpine soils: An experimental study in the Wind River Range (Wyoming, USA)

Climate change and a related increase in temperature, particularly in alpine areas, force both flora and fauna to adapt to the new conditions. These changes should in turn affect soil formation processes. The aim of this study was to identify possible consequences for soils in a dry-alpine region with respect to weathering of primary minerals and leaching of elements under expected vegetation and climate changes. To achieve this, a field empirical approach investigating an altitudinal sequence was used in combination with laboratory weathering experiments simulating several scenarios. The study sites are located in Sinks Canyon and Stough Basin of the Wind River Range, Wyoming, USA. The following sites (from moist to dry with increasing temperature along the sequence) were investigated: 10 soil profiles (Typic Haplocryoll) in a tundra ecotone, 10 soil profiles (Ustic Haplocryoll) in a pine-fir forest and 20 soil profiles (Ustic Argicryoll) in sagebrush. All soils developed on granitoid moraines. Soil mineralogy was analysed using cathodoluminescence and X-ray diffraction. This revealed that biotite and plagioclase were both weathered to smectite while plagioclase also weathered to kaolinite. Cooler, wetter, altitude-dependent conditions promoted weathering of primary minerals. Furthermore, the soils of the tundra and forest zone exhibited a higher acidity and more organic carbon.In a series of wet laboratory batch experiments, materials from topsoils (A horizons) and subsoils (B horizons) in each ecotone were examined alone or in combination with other samples. In a first step, aqueous extracts of the topsoil samples were generated in batch reactors and analysed for the main ions. In a second and a third step the topsoil extracts were reacted with the subsoil samples of the same ecotone, and with the subsoil samples of the ecotones at higher altitude. The total duration of these batch experiments was 1800h, and the solutes were measured using ICP-OES and ion chromatography. Dissolved Ca, Mg and K were mainly controlled by the chemical weathering of oligoclase, K-feldspar and biotite. With increasing altitude the total concentrations of Ca, Mg and K in the aqueous extracts decreased, the relative ionic contribution from K decreased, while the ionic contribution from Ca increased.Climate change (warming, changed precipitation) potentially will reduce weathering intensity, soil acidity and the content of organic carbon. An altitudinal shift in vegetation due to climate change seems to affect the ionic composition of the soil solution. In the case of a shift from forest to sagebrush and tundra to forest or sagebrush, the relative contribution from K would increase at the expense of Ca. We hypothesise that K will play an important role in future biogeochemical cycles under the assumptions of climate warming and subsequent vegetation shifts to higher altitudes.

Impact of Intensive Greenhouse Production System on Soil Quality

Composite top- and subsoil samples were collected from the greenhouses in the Al-Balawneh area, Jordan, where intensive greenhouse production system (IGPS) has been practiced since 1998, to study the impact of IGPS on soil quality as measured by the chemical and biological properties to develop a sustainable production system. The study showed that IGPS led to higher electrical conductivity in top- and subsoils compared to an uncultivated soil (control). Quality and amount of irrigation water, lack of efficient drainage, and quantity and types of applied fertilizers were major factors resulting in salt buildup. IGPS resulted in lower total N (TN) and NO3-N in the soil compared to the control. The lower TN was due to crop uptake, microbial immobilization, volatilization, and irregular application of composted animal manure or poultry manure. In contrast, higher residual Olsen-P content was detected in both soil layers of greenhouses than in the control. Residual P was classified as very high in the topsoil layers and sufficient to high in the subsoil layers. Residual available K in the soils of greenhouses was relatively lower than that in the control and it was, however, classified as high to very high. A large increase of Cl and a considerable decrease in the bacterial count were observed in both soil layers of IGPS compared to the control treatment. Economically sustainable soil management practices need to be adopted by farmers to achieve a sustainable and profitable production. This can be accomplished through education, targeted towards the farming community in the central Jordan Valley.

Geochemical assessment of steel smelter-impacted urban soils, Ahvaz, Iran

Geochemical study of urban soils is a challenging work due to high diversity of urban areas and multiple influences of anthropogenic sources on the soil geochemical composition. In the present study, a soil geochemical survey has been performed to determine the spatial distribution and possible sources of metals in the area around the Iran National Steel Industrial Group (INSIG). Concentrations of metals (Cr, Ni, Mn, Zn, Cu, Pb, V, Co and Fe) were determined in 63 topsoil (0–20cm) and 46 subsoil (40–50cm) samples. In addition, the pH, soil organic carbon (SOC), cation exchange capacity (CEC), soil grain sizes and CaCO3 were measured for each sample. The mean concentrations of Cr, Ni, Mn, Zn, Cu, Pb, V and Co in the topsoils were 556mg/kg, 261mg/kg, 2204mg/kg, 1716mg/kg, 157/kg, 122mg/kg, 177mg/kg and 41mg/kg, respectively. This study is based on comparisons of statistical parameters, the spatial distribution of studied elements and the results of hierarchical cluster analysis (HCA) and principal component analysis (PCA). Four natural geochemical associations and one anthropogenic geochemical association were identified for the topsoil layer. Natural geochemical associations (sand, silt and CEC), (Cr, Ni and V), (Co and clay) and (pH) are mainly influenced by geogenic/pedogenic factors, while anthropogenic association (Mn, Zn, Cu, Pb, Fe, SOC and CaCO3) is related to anthropogenic activities in the study area. The principal component analysis of the subsoil data set revealed four main components: the “anthropogenic specific” association of (Zn, Cu, Pb, Fe, SOC and CaCO3) and three “natural specific” associations of (pH, sand, silt and CEC), (Cr, Ni, V and Co) and (Mn and clay). A distinct anomaly of anthropogenically introduced metals was found in soils closer to the steel smelter in the N–SE axes of the study area. The results of HCA and correlation analyses for the data sets of two soil layers suggested that chelated elements (Zn, Cu, Pb and Fe) by soil organic fraction were transported down to the subsurface layer (40–50cm). According to the Canadian Soil Quality Guidelines, Cr, Ni, Mn, Zn and Cu were the primary critical metals in the both soil layers. This study may provide decision makers with the useful information for management practices to protect human health.

Speciation of Heavy Metals by Modified BCR Sequential Extraction in Soils Contaminated by Phosphogypsum in Sfax, Tunisia

The accumulation of trace metals in soil is a serious environmental problem that creates a hazard when metals are transferred to water or plants. To understand the mobility and bioavailability of trace metals, the concentrations and distributions of trace metals must be established for different physical and chemical phases of the soil. We determined the concentrations of trace metals (Zn, Pb, Cu, Cr, Co, Ni, Mn, and Fe) in soil using the sequential extraction method recommended by Community Bureau of Reference (BCR) and analysed chemical properties, such as the pH, cation exchange capacity, total organic carbon, electrical conductivity, and calcium carbonate. Our results revealed higher concentrations of trace metals in topsoil samples (0–20 cm) than in subsoil samples (20–40 cm and 40–60 cm) for most metals at four sites. Zn in the topsoil was mostly associated with the non-resistant fraction at all sites. Approximately 60% more Pb was bound to the non-residual, exchangeable and reducible fractions at all sites, and soil depths. Cr, Cu, Ni and Fe were mainly in the residual fraction, whereas Mn was largely present in the non-resistant fraction. The global contamination factor of trace metals decreased with soil depth. The mobility and bioavailability were greatest for Zn, followed by Cu and Pb. DOI: http://dx.doi.org/10.5755/j01.erem.70.4.7807