Applied and Environmental Soil Science The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Soil Microbial Community Structure and Target Organisms under Different Fumigation Treatments Thu, 26 Mar 2015 09:57:07 +0000 Producers of several high-value crops in California rely heavily on soil fumigants to control key diseases, nematodes, and weeds. Fumigants with broad biocidal activity can affect both target and nontarget soil microorganisms. The ability of nontarget soil microorganisms to recover after fumigation treatment is critical because they play an important role in sustaining the health of agricultural and natural soil systems. Fumigation trial was conducted in Parlier, CA, and the study focuses on the effects of different rates of Telone C35 and also methyl bromide fumigation with polyethylene (PE) and totally impermeable film (TIF) tarps on target and nontarget soil microorganisms using field samples. Results indicated that the populations of target organisms, such as Fusarium oxysporum and Pythium spp., were reduced at all rates of fumigants. Phospholipid fatty acid (PLFA) analysis indicated that all major nontarget soil microbial groups such as Gram positive bacteria, Gram negative bacteria, fungi, and arbuscular mycorrhizal fungi (AMF) were affected by methyl bromide (MeBr) fumigation treatment. In general, the effects of Telone C35 (299 L/ha) under PE tarp had the least impact on microbial community structure and better effect on controlling target microorganisms and, therefore, indicated the better option among fumigation treatments. Sadikshya R. Dangi, James S. Gerik, Rebecca Tirado-Corbalá, and Husein Ajwa Copyright © 2015 Sadikshya R. Dangi et al. All rights reserved. Phosphorus Status, Inorganic Phosphorus Forms, and Other Physicochemical Properties of Acid Soils of Farta District, Northwestern Highlands of Ethiopia Mon, 16 Mar 2015 16:24:43 +0000 Soil acidity and low availability of P limit crop production in the highlands of Ethiopia. The objective of this study was to determine the P status, distribution and forms of inorganic P and relate them to selected chemical properties of eight representative acidic surface soil samples from Farta District. Soil pH (H2O) varied between 4.74 and 5.50. The moderate to high CEC suggests that besides kaolinite, the soils also contain expandable 2 : 1 clay minerals. Though the total P content was high, the available Olsen P content was very low or low in all soils except one. In most soils, the abundance of inorganic P fractions was as follows: P bound by oxalate extractable iron (-P) reductant soluble Fe-P occluded Al-Fe-P P bound by oxalate extractable aluminum (-P) calcium bound P (Ca-P). Olsen P had a very strong positive correlation () with -P (), -P (), and oxalate extractable P (). Though Fe bound P reserves were quite abundant and the degree of P saturation of + (median 3.3%) was moderate, the extremely low P saturation of (median 0.5%) explains the P deficiency of the soils. Asmare Melese, Heluf Gebrekidan, Markku Yli-Halla, and Birru Yitaferu Copyright © 2015 Asmare Melese et al. All rights reserved. Artificial Neural Networks for Estimating Soil Water Retention Curve Using Fitted and Measured Data Mon, 16 Mar 2015 13:31:20 +0000 Artificial neural networks for estimating the soil water retention curve have been developed considering measured data and require a large quantity of soil samples because only retention curve data obtained for the same set of matric potentials can be used. In order to preclude this drawback, we present two ANN models which tested the performance of ANNs trained with fitted water contents data. These models were compared to a recent new ANN approach for predicting water retention curve, the pseudocontinuous pedotransfer functions (PTFs), which is also an attempt to deal with limited data. Additionally, a sensitivity analysis was carried out to verify the influence of each input parameter on each output. Results showed that fitted ANNs provided similar statistical indexes in predicting water contents to those obtained by the pseudocontinuous method. Sensitivity analysis revealed that bulk density and porosity are the most important parameters for predicting water contents in wet regime, whereas sand and clay contents are more significant in drier conditions. The sensitivity analysis for the pseudocontinuous method demonstrated that the natural logarithm of the matric potential became the most important parameter, and the influences of all other inputs were reduced to be not relevant, except the bulk density. Tirzah Moreira de Melo and Olavo Correa Pedrollo Copyright © 2015 Tirzah Moreira de Melo and Olavo Correa Pedrollo. All rights reserved. Microrelief-Controlled Overland Flow Generation: Laboratory and Field Experiments Mon, 09 Mar 2015 07:26:08 +0000 Surface microrelief affects overland flow generation and the related hydrologic processes. However, such influences vary depending on other factors such as rainfall characteristics, soil properties, and initial soil moisture conditions. Thus, in-depth research is needed to better understand and evaluate the combined effects of these factors on overland flow dynamics. The objective of this experimental study was to examine how surface microrelief, in conjunction with the factors of rainfall, soil, and initial moisture conditions, impacts overland flow generation and runoff processes in both laboratory and field settings. A series of overland flow experiments were conducted for rough and smooth surfaces that represented distinct microtopographic characteristics and the experimental data were analyzed and compared. Across different soil types and initial moisture conditions, both laboratory and field experiments demonstrated that a rough soil surface experienced a delayed initiation of runoff and featured a stepwise threshold flow pattern due to the microrelief-controlled puddle filling-spilling-merging dynamics. It was found from the field experiments that a smooth plot surface was more responsive to rainfall variations especially during an initial rainfall event. However, enhanced capability of overland flow generation and faster puddle connectivity of a rough field plot occurred during the subsequent rain events. Xuefeng Chu, G. Padmanabhan, and Daniel Bogart Copyright © 2015 Xuefeng Chu et al. All rights reserved. Phosphorus Sorption Kinetics in Reclaimed Lignite Mine Soils under Different Age Stands of Robinia pseudoacacia L. in Northeast Germany Wed, 18 Feb 2015 15:48:18 +0000 The objectives of the work were to study phosphorus (P) dynamics in postmining soils under short rotation coppices at different stages of Robinia pseudoacacia L. growth (2, 3, 4, and 14 years old). From the results obtained, the amount of total P, total organic P, plant available P, and P stock increased with increasing age of R. pseudoacacia. However, values were very low compared to that recommended for optimum plant growth, reflecting a general deficit in P. Additionally, the P sorption and desorption processes were investigated. The total P sorption capacity obtained from the laboratory experiments was on average, 2.5 times greater for soils under the oldest R. pseudoacacia than values measured at the younger sites. Values of P saturation factor (α) were comparatively lower compared to that reported in the literature. This may be attributed primarily to the less P saturation of the postmining soils, coupled with rather small contents of oxalate iron and aluminium (sum of 47 mmol kg−1). Results demonstrate significant difference between 2 and 14 years old R. pseudoacacia; thus establishing of short rotation coppice (SRC) on degraded marginal sites may be a valuable method of soil reclamations. Anna Slazak and Dirk Freese Copyright © 2015 Anna Slazak and Dirk Freese. All rights reserved. Short-Term Effects of Biogas Digestates and Pig Slurry Application on Soil Microbial Activity Tue, 13 Jan 2015 11:49:52 +0000 The effect of four biogas digestates (BD-A, BD-B, BD-C, and BD-D) and pig slurry (PS) on soil microbial functions was assessed at application rates corresponding to 0–1120 kg -N ha−1. At dose corresponding to 140 kg -N ha−1, 30.9–32.5% of the carbon applied in BD-A, BD-C, and PS was utilized during 12 days, while for BD-B and BD-D corresponding utilization was 19.0 and 16.9%, respectively. All BDs resulted in net nitrogen assimilation at low rates (17.5–140 kg -N ha−1) but net mineralization dominated at higher rates. PS resulted in net mineralization at all application rates. All residues inhibited potential ammonium oxidation (PAO), with EC50-values ranging between 45 and 302 kg -N ha−1. Low rates of BDs appeared to weakly stimulate potential denitrification activity (PDA), while higher rates resulted in logarithmic decrease. The EC50-values for PDA were between 238 and 347 kg -N ha−1. No inhibition of PDA was observed after amendment with PS. In conclusion, biogas digestates inhibited ammonia oxidation and denitrification, which could be an early warning of potential hazardous substances in the digestates. However, this effect can also be regarded as positive, since it may reduce nitrogen losses. J. Abubaker, K. Risberg, E. Jönsson, A. S. Dahlin, H. Cederlund, and M. Pell Copyright © 2015 J. Abubaker et al. All rights reserved. Leaching of Chromium, Copper, and Arsenic from CCA-Treated Utility Poles Thu, 18 Dec 2014 09:28:35 +0000 Concentrations of Cu, Cr, and As in soils surrounding 26 Douglas Fir Chromated Copper Arsenate (CCA) treated utility poles and in rainwater runoff from a new CCA treated utility pole segment (log) suspended outside in a cylinder were studied. The age of the utility poles, distances from the poles, rainfall amounts, and characteristics of soil samples including cation exchange capacity (CEC), pH, and total organic carbon (TOC) were considered. Heavier rainfall, damp conditions, and more weathered poles contributed to the greatest leaching of Cu, Cr, and As. The maximum measured soil concentrations of Cu, Cr, and As were 37.5, 65.5, and 38.9 mmol/kg and maximum Cu, Cr, and As concentrations in rainwater run-off were 14, 77.7 and 55.8 μmol/L. Metal concentrations decreased with distance from the poles and, except at one utility pole location, Cu was the most leached of the three elements. The As appeared to have greater mobility in the soil than the Cr. Along the transmission line nearest the coast and from which the greatest amount of samples was collected, soil CEC and TOC values were the highest and the CEC and TOC were directly and strongly correlated. Cynthia A. Coles, Joseph A. Arisi, Marion Organ, and Geoff I. Veinott Copyright © 2014 Cynthia A. Coles et al. All rights reserved. Assessment of the Effectiveness of Ectomycorrhizal Inocula to Promote Growth and Root Ectomycorrhizal Colonization in Pinus patula Seedlings Using the Most Probable Number Technique Mon, 08 Dec 2014 09:12:44 +0000 The aim of this study was to evaluate the response of Pinus patula seedlings to two inocula types: soil from a Pinus plantation (ES) and an in vitro produced inoculum (EM). The most probable number method (MPN) was used to quantify ectomycorrhizal propagule density (EPD) in both inocula in a 7-order dilution series ranging from 100 (undiluted inoculum) to 10−6 (the most diluted inoculum). The MPN method allowed establishing differences in the number of infective ectomycorrhizal propagules’ density (EPD) ( per g; per g). The results suggest that the EPD of an inoculum may be a key factor that influences the successfulness of the inoculation. The low EPD of the ES inoculum suggests that soil extracted from forest plantations had very low effectiveness for promoting root colonization and plant growth. In contrast, the high EPD found in the formulated inoculum (EM) reinforced the idea that it is better to use proven high quality inocula for forest nurseries than using soil from a forestry plantation. Manuel Restrepo-Llano, Nelson W. Osorio, and Juan D. León Copyright © 2014 Manuel Restrepo-Llano et al. All rights reserved. DOC and CO2-C Releases from Pristine and Drained Peat Soils in Response to Water Table Fluctuations: A Mesocosm Experiment Thu, 27 Nov 2014 06:26:16 +0000 Hydrological conditions are considered to be among the main drivers influencing the export of dissolved organic carbon (DOC) from terrestrial to aquatic ecosystems, and hydrology is likely to alter due to climate change. We built a mesocosm experiment by using peat profiles from a pristine and from a drained (drained in 1978) peatland. A several-week-long low water table period followed by a high water table period, that is, a setting mimicking drought followed by flood, released relatively more DOC from pristine peat than from drained peat. From pristine peat profiles DOC was released into soil water in such quantities that the concentration of DOC remained stable despite dilution caused by added spring water to the mesocosms. In drained peat the DOC concentrations decreased during the high water table period indicating stronger dilution effect in comparison to pristine peat. At the landscape level DOC load from a drained peatland to the recipient water body may, however, increase during flooding because of high water runoff out of the peatland containing high DOC concentrations relative to the forest and agricultural areas. During the high water table period neither peat type nor water table had any clear impact on carbon dioxide (CO2-C) fluxes. Merjo P. P. Laine, Rauni Strömmer, and Lauri Arvola Copyright © 2014 Merjo P. P. Laine et al. All rights reserved. Litter Controls Earthworm-Mediated Carbon and Nitrogen Transformations in Soil from Temperate Riparian Buffers Sun, 14 Sep 2014 09:09:01 +0000 Nutrient cycling in riparian buffers is partly influenced by decomposition of crop, grass, and native tree species litter. Nonnative earthworms in riparian soils in southern Quebec are expected to speed the processes of litter decomposition and nitrogen (N) mineralization, increasing carbon (C) and N losses in gaseous forms or via leachate. A 5-month microcosm experiment evaluated the effect of Aporrectodea turgida on the decomposition of 3 litter types (deciduous leaves, reed canarygrass, and soybean stem residue). Earthworms increased CO2 and N2O losses from microcosms with soybean residue, by 112% and 670%, respectively, but reduced CO2 and N2O fluxes from microcosms with reed canarygrass by 120% and 220%, respectively. Litter type controlled the CO2 flux (soybean ≥ deciduous-mix litter = reed canarygrass > no litter) and the N2O flux (soybean ≥ no litter ≥ reed canarygrass > deciduous-mix litter). However, in the presence of earthworms, there was a slight increase in C and N gaseous losses of C and N relative to their losses via leachate, across litter treatments. We conclude that litter type determines the earthworm-mediated decomposition effect, highlighting the importance of vegetation management in controlling C and N losses from riparian buffers to the environment. Maria Kernecker, Joann K. Whalen, and Robert L. Bradley Copyright © 2014 Maria Kernecker et al. All rights reserved. Tillage System Affects Soil Organic Carbon Storage and Quality in Central Morocco Tue, 02 Sep 2014 09:52:44 +0000 Stabilizing or improving soil organic carbon content is essential for sustainable crop production under changing climate conditions. Therefore, soil organic carbon research is gaining momentum in the Mediterranean basin. Our objective is to quantify effects of no tillage (NT) and conventional tillage (CT) on soil organic carbon stock (SOCs) in three soil types (Vertisol, Cambisol, and Luvisol) within Central Morocco. Chemical analyses were used to determine how tillage affected various humic substances. Our results showed that, after 5 years, surface horizon (0–30 cm) SOC stocks varied between tillage systems and with soil type. The SOCs was significantly higher in NT compared to CT (10% more in Vertisol and 8% more in Cambisol), but no significant difference was observed in the Luvisol. Average SOCs within the 0–30 cm depth was 29.35 and 27.36 Mg ha−1 under NT and CT, respectively. The highest SOCs (31.89 Mg ha−1) was found in Vertisols under NT. A comparison of humic substances showed that humic acids and humin were significantly higher under NT compared to CT, but fulvic acid concentrations were significantly lower. These studies confirm that NT does have beneficial effects on SOCs and quality in these soils. R. Moussadek, R. Mrabet, R. Dahan, A. Zouahri, M. El Mourid, and E. Van Ranst Copyright © 2014 R. Moussadek et al. All rights reserved. Heavy Metal Polluted Soils: Effect on Plants and Bioremediation Methods Tue, 12 Aug 2014 11:48:39 +0000 Soils polluted with heavy metals have become common across the globe due to increase in geologic and anthropogenic activities. Plants growing on these soils show a reduction in growth, performance, and yield. Bioremediation is an effective method of treating heavy metal polluted soils. It is a widely accepted method that is mostly carried out in situ; hence it is suitable for the establishment/reestablishment of crops on treated soils. Microorganisms and plants employ different mechanisms for the bioremediation of polluted soils. Using plants for the treatment of polluted soils is a more common approach in the bioremediation of heavy metal polluted soils. Combining both microorganisms and plants is an approach to bioremediation that ensures a more efficient clean-up of heavy metal polluted soils. However, success of this approach largely depends on the species of organisms involved in the process. G. U. Chibuike and S. C. Obiora Copyright © 2014 G. U. Chibuike and S. C. Obiora. All rights reserved. Uranium Leaching from Contaminated Soil Utilizing Rhamnolipid, EDTA, and Citric Acid Tue, 22 Jul 2014 11:45:06 +0000 Biosurfactants have recently gained attention as “green” agents that can be used to enhance the remediation of heavy metals and some organic matter in contaminated soils. The overall objective of this paper was to investigate rhamnolipid, a microbial produced biosurfactant, and its ability to leach uranium present in contaminated soil from an abandoned mine site. Soil samples were collected from two locations in northern Arizona: Cameron (site of open pit mining) and Leupp (control—no mining). The approach taken was to first determine the total uranium content in each soil using a hydrofluoric acid digestion, then comparing the amount of metal removed by rhamnolipid to other chelating agents EDTA and citric acid, and finally determining the amount of soluble metal in the soil matrix using a sequential extraction. Results suggested a complex system for metal removal from soil utilizing rhamnolipid. It was determined that rhamnolipid at a concentration of 150 μM was as effective as EDTA but not as effective as citric acid for the removal of soluble uranium. However, the rhamnolipid was only slightly better at removing uranium from the mining soil compared to a purified water control. Overall, this study demonstrated that rhamnolipid ability to remove uranium from contaminated soil is comparable to EDTA and to a lesser extent citric acid, but, for the soils investigated, it is not significantly better than a simple water wash. Sara Asselin and Jani C. Ingram Copyright © 2014 Sara Asselin and Jani C. Ingram. All rights reserved. Crop Diversity Effects on Near-Surface Soil Condition under Dryland Agriculture Tue, 22 Jul 2014 08:07:06 +0000 Unprecedented changes in agricultural land use throughout the northern Great Plains of North America have highlighted the need to better understand the role of crop diversity to affect ecosystem services derived from soil. This study sought to determine the effect of four no-till cropping systems differing in rotation length and crop diversity on near-surface (0 to 10 cm) soil properties. Cropping system treatments included small grain-fallow (SG-F) and three continuously cropped rotations (3 yr, 5 yr, and Dynamic) located in south-central North Dakota, USA. Soil pH was lower in the 3 yr rotation (5.17) compared to the Dynamic (5.51) and SG-F (5.55) rotations . Among cropping system treatments, 5 yr and Dynamic rotations possessed significantly greater soil organic C (SOC) and total N (mean = 26.3 Mg C ha−1, 2.5 Mg N ha−1) compared to the 3 yr (22.7 Mg C ha−1, 2.2 Mg N ha−1) and SG-F (19.9 Mg C ha−1, 2.0 Mg N ha−1) rotations . Comparison of SOC measured in this study to baseline values at the research site prior to the establishment of treatments revealed only the 5 yr and Dynamic rotations increased SOC over time. The results of this study suggest that a diverse portfolio of crops is necessary to minimize soil acidification and increase SOC. Mark A. Liebig, David W. Archer, and Don L. Tanaka Copyright © 2014 Mark A. Liebig et al. All rights reserved. Establishing Land Suitability Criteria for Cashew (Anacardium occidentale L.) in Indonesia Tue, 22 Jul 2014 00:00:00 +0000 Commodity development requires site selection which should be established prior to large scale development. The land suitability criteria for cashew are not presently available. The relationship between the biophysical aspects, especially land and soil with commodity productivity, is also not known in depth. The objective of this study is to establish the criteria of land suitability for cashew in Indonesia, based on its production and land characteristics. Cashew plantations in 5 provinces were sampled. The data of production per tree per year were obtained from farmers, while the soil was sampled and analyzed in the laboratory. Age-adjusted cashew production was used as the yield response and plotted against land characteristics. Boundary lines resulting from the scatter of points were described; these lines produced the limits of land suitability criteria. The criteria were established using a projection of the intersection between the boundary line and yield interval. The criteria were also built in accordance with the productivity index of FAO for the internal boundary inside the S (suitable) class and by calculating the break-event point production for the boundary between S (suitable) and N (nonsuitable) order. The main result of this research is land suitability criteria for cashew. Widiatmaka, Atang Sutandi, Anas Iswandi, Usman Daras, Muhammad Hikmat, and Ari Krisnohadi Copyright © 2014 Widiatmaka et al. All rights reserved. Survival of a Rifampicin-Resistant Pseudomonas fluorescens Strain in Nine Mollisols Mon, 21 Jul 2014 07:21:38 +0000 Pseudomonas fluorescens strain D7 (P.f. D7) is a naturally occurring soil bacterium that shows promise as a biological herbicide to inhibit growth of annual grass weeds, including downy brome (Bromus tectorum L.), in crop- and rangelands. Pseudomonas fluorescens strain D7rif (P.f. D7rif) is a rifampicin-resistant strain of P.f. D7. One of the greatest obstacles to successful biological weed control is survival of the organism under field conditions. Nine soils in the taxonomic order of Mollisols, collected from downy brome-infested areas of the Western and Central United States, were inoculated with P.f. D7rif and incubated in the laboratory to determine the effects of soil type, soil properties, incubation temperature, and soil water potential on survival of P.f. D7rif over 63 days. Silt loam soils from Lind, Washington, and Moro, Oregon, sustained the highest P.f. D7rif populations, and recovery was the lowest from Pendleton, Oregon soil. Survival and recovery of P.f. D7rif varied with soil type and temperature but not with the two soil water potentials tested. After 63 days, P.f. D7rif was recovered at levels greater than log 5.5 colony forming units (CFU) g−1 soil from five of the nine test soils, a level adequate to suppress downy brome under field or range conditions. Tami L. Stubbs, Ann C. Kennedy, and Horace D. Skipper Copyright © 2014 Tami L. Stubbs et al. All rights reserved. Potential of Igniscum sachalinensis L. and Salix viminalis L. for the Phytoremediation of Copper-Contaminated Soils Wed, 09 Jul 2014 07:48:44 +0000 The potential of Salix viminalis L. and Igniscum sachalinensis L. for phytoremediation of copper- (Cu-) contaminated soils was studied under greenhouse conditions. Approximately 5 kg of potted agricultural and sewage amended soils sampled from the top 0 to 20 cm depth in Neuruppin, Germany, was treated with CuSO4 at concentrations 0 (control), 250, 750, and 1250 mg Cu kg−1 soil and ethylenediaminetetraacetic acid (EDTA) at 1000 mg kg−1 soil, respectively. Each plant species was grown on four replicates of each soil treatment. Copper accumulated in aboveground tissues tends to increase with increasing soil Cu concentration and was the lowest in stem and leaf of both plant species grown on control soils. At 750 and 1250 mg Cu kg−1 soil, Cu accumulated in stem and leaf of I. sachalinensis increased by over 12- and 20-fold, respectively, whereas there was no vegetative growth in S. viminalis beyond 250 mg Cu kg−1 soil. Application of EDTA to sewage amended soils increased Cu accumulated in the stem and leaf, especially in I. sachalinensis. In general, I. sachalinensis seems to have the potential to tolerate high soil Cu content and simultaneously bioaccumulate Cu in tissues and thus may have better prospects for phytoremediation. Isong Godlove Tingwey, Seth Nii-Annang, and Dirk Freese Copyright © 2014 Isong Godlove Tingwey et al. All rights reserved. Determination of Biological Nitrogen Fixation Induced N2O Emission from Arable Soil by Using a Closed Chamber Technique Mon, 07 Jul 2014 09:09:44 +0000 Intensive use of mineral N fertilizers and organic amendments has resulted in higher N2O emissions. A growing worldwide concern for these problems has motivated researchers, environmentalists, and policy makers to find alternatives to overcome such losses. Biological nitrogen fixation is one of many natural biological approaches to minimize the use of fertilizers and to possibly reduce N2O emissions. A greenhouse study was performed by growing inoculated and noninoculated soybean seeds (Glycine max (L.) Merr.) in PVC columns. The objective was to measure the contribution of Bradyrhizobium Japonicum and mineral-N fertilizer to promoting N2O emission. A closed chamber technique was used for gas sampling. N2O measurements were carried out shortly after nodulation. Bradyrhizobium Jopanicum induced N2O cumulative (121.8 μg kg−1) fluxes of inoculated seeds was significantly (α = 0.05) higher than those of mineral N fertilized treatment (NIS) and the control (bare soil). Total nitrogen content of the roots and seeds was not affected by inoculation. Total carbon ( 42.1  ±  0.1%), total nitrogen (3.1  ±  0.1%), and crude protein (19.9  ±   0.7%) contents of leaves of the inoculated seeds were significantly higher than those of noninoculated seed treatments. N2O fluxes significantly increased with high dissolved organic carbon content (70.77  ±  3.99  mg L−1) at R3 and at R8 stages when (39.60  ±  0.94 mg L−1) concentrations were high. Ambreen Shah Copyright © 2014 Ambreen Shah. All rights reserved. Comparison of Three Supervised Learning Methods for Digital Soil Mapping: Application to a Complex Terrain in the Ecuadorian Andes Tue, 20 May 2014 07:15:05 +0000 A digital soil mapping approach is applied to a complex, mountainous terrain in the Ecuadorian Andes. Relief features are derived from a digital elevation model and used as predictors for topsoil texture classes sand, silt, and clay. The performance of three statistical learning methods is compared: linear regression, random forest, and stochastic gradient boosting of regression trees. In linear regression, a stepwise backward variable selection procedure is applied and overfitting is controlled by minimizing Mallow’s Cp. For random forest and boosting, the effect of predictor selection and tuning procedures is assessed. 100-fold repetitions of a 5-fold cross-validation of the selected modelling procedures are employed for validation, uncertainty assessment, and method comparison. Absolute assessment of model performance is achieved by comparing the prediction error of the selected method and the mean. Boosting performs best, providing predictions that are reliably better than the mean. The median reduction of the root mean square error is around 5%. Elevation is the most important predictor. All models clearly distinguish ridges and slopes. The predicted texture patterns are interpreted as result of catena sequences (eluviation of fine particles on slope shoulders) and landslides (mixing up mineral soil horizons on slopes). Martin Hitziger and Mareike Ließ Copyright © 2014 Martin Hitziger and Mareike Ließ. All rights reserved. Arsenic, Chromium, and Other Potentially Toxic Elements in the Rocks and Sediments of Oropos-Kalamos Basin, Attica, Greece Tue, 06 May 2014 12:38:08 +0000 Rocks and sediments are non-anthropogenic sources of elements contamination. In this study, a series of potentially toxic elements were quantified in rocks and sediments of the Oropos-Kalamos basin. Only As, Hg, Pb, and Sb contents, in all the examined rocks and sediments, were higher than the levels given in international literature. Concentration of the elements As, Cr, Hg, Mo, Ni, and U is highly elevated in the lignite compared to crustal element averages. The enrichment of Cr and Ni in the lignite can be attributed to the known ultramafic rock masses surrounding the basin, while enrichment of As, Hg, Mo, Sb, and U is associated with the past geothermal activity of the Upper Miocene (about 15 million years ago). Nickel and Cr were transported into the lignite deposition basin by rivers and streams draining ultramafic rock bodies. The results of this study imply the natural source of Cr3+ and Cr6+ contamination of the Oropos-Kalamos groundwater, since high Cr contents were also recorded in the lignite (212.3 mg kg−1), chromiferous iron ore occurrences (256.6 mg kg−1), and alluvial deposits (212.5 mg kg−1), indicating Cr leaching and transportation to the depositional basin dating from the Upper Miocene age. D. Alexakis and D. Gamvroula Copyright © 2014 D. Alexakis and D. Gamvroula. All rights reserved. Spatial Variability of Physical Soil Quality Index of an Agricultural Field Sun, 04 May 2014 06:48:46 +0000 A field investigation was carried out to evaluate the spatial variability of physical indicators of soil quality of an agricultural field and to construct a physical soil quality index (SQ) map. Surface soil samples were collected using m grid from an Inceptisol on Ganges Tidal Floodplain of Bangladesh. Five physical soil quality indicators, soil texture, bulk density, porosity, saturated hydraulic conductivity (), and aggregate stability (measured as mean weight diameter, MWD) were determined. The spatial structures of sand, clay, and were moderate but the structure was strong for silt, bulk density, porosity, and MWD. Each of the physical soil quality indicators was transformed into 0 and 1 using threshold criteria which are required for crop production. The transformed indicators were the combined into SQ. The kriged SQ map showed that the agricultural field studied could be divided into two parts having “good physical quality” and “poor physical soil quality.” Sheikh M. Fazle Rabbi, Bina R. Roy, M. Masum Miah, M. Sadiqul Amin, and Tania Khandakar Copyright © 2014 Sheikh M. Fazle Rabbi et al. All rights reserved. Mechanical Mastication of Utah Juniper Encroaching Sagebrush Steppe Increases Inorganic Soil N Sun, 27 Apr 2014 13:43:40 +0000 Juniper (Juniperus spp.) has encroached on millions of hectares of sagebrush (Artemisia spp.) steppe. Juniper mechanical mastication increases cover of understory species but could increase resource availability and subsequently invasive plant species. We quantified the effects of juniper mastication on soil resource availability by comparing total C, total N, C : N ratio, Olsen extractable P, sulfate S, and pH using soil samples and inorganic N () using ion exchange membranes. We compared resource availability in paired masticated and untreated areas in three juniper-dominated sagebrush and bunchgrass ecosystems in the Utah portion of the Great Basin. Inorganic N was 4.7 times higher in masticated than in untreated areas across seasons (). Within masticated areas, tree mounds of juniper leaf scales and twigs served as resource islands with 1.9 times higher inorganic N and total C, and 2.8 times higher total N than bare interspaces across seasons (). Bare interspaces had 3.0–3.4 times higher inorganic N than interspaces covered with masticated trees during late-summer through winter (). Soil fertility changes associated with mastication were not considered sufficient to favor establishment of annual over perennial grasses, and we expect both to increase in cover following juniper mastication. Kert R. Young, Bruce A. Roundy, and Dennis L. Eggett Copyright © 2014 Kert R. Young et al. All rights reserved. Soil Erosion Prediction Using Morgan-Morgan-Finney Model in a GIS Environment in Northern Ethiopia Catchment Tue, 22 Apr 2014 11:51:33 +0000 Even though scientific information on spatial distribution of hydrophysical parameters is critical for understanding erosion processes and designing suitable technologies, little is known in Geographical Information System (GIS) application in developing spatial hydrophysical data inputs and their application in Morgan-Morgan-Finney (MMF) erosion model. This study was aimed to derive spatial distribution of hydrophysical parameters and apply them in the Morgan-Morgan-Finney (MMF) model for estimating soil erosion in the Mai-Negus catchment, northern Ethiopia. Major data input for the model include climate, topography, land use, and soil data. This study demonstrated using MMF model that the rate of soil detachment varied from <20 t ha−1 y−1 to >170 t ha−1 y−1, whereas the soil transport capacity of overland flow (TC) ranged from 5 t ha−1 y−1 to >42 t ha−1 y−1. The average soil loss estimated by TC using MMF model at catchment level was 26 t ha−1 y−1. In most parts of the catchment (>80%), the model predicted soil loss rates higher than the maximum tolerable rate (18 t ha−1 y−1) estimated for Ethiopia. Hence, introducing appropriate interventions based on the erosion severity predicted by MMF model in the catchment is crucial for sustainable natural resources management. Gebreyesus Brhane Tesfahunegn, Lulseged Tamene, and Paul L. G. Vlek Copyright © 2014 Gebreyesus Brhane Tesfahunegn et al. All rights reserved. Characterization of Environmental Nano- and Macrocolloid Particles Extracted from Selected Soils and Biosolids Mon, 14 Apr 2014 09:28:04 +0000 Environmental nanoparticles found in soil systems and biosolids may pose a considerable risk to groundwater quality as contaminant carriers. Little effort has been invested in the characterization of natural nanocolloids compared to corresponding macrocolloids. This study involved physicochemical, mineralogical, and morphological characterizations of nanocolloids and macrocolloids fractionated from three Kentucky soils and one biosolid. Particle size and morphology were investigated using scanning/transmission electron microscopy and dynamic light scattering. Mineralogical composition was determined by X-ray diffraction and thermogravimetric and Fourier-transform infrared spectroscopy analyses. Zeta potentials and cation exchange capacities assessed surface charge and chemical reactivity. The estimated average hydrodynamic diameter of nanoparticles was nearly twice the ideal 100 nm range, apparently due to irregular particle shapes and partial aggregation. Nanoparticles were also found attached to surfaces of macrocolloids, forming macro-nano aggregates and obscuring some of their physical and chemical characteristics. However, nanocolloids exhibited greater surface reactivity, likely due to their smaller size, poor crystallinity, and morphological shape distortions. In spite of some behavior modification due to nanoaggregation phenomena, nanocolloids appeared to be much more potent vectors of contaminant transport in subsurface environments than their macrosize fractions. Nevertheless, their heterogeneous nature brings to light important considerations in addressing pollution prevention and remediation challenges. J. L. Ghezzi, A. D. Karathanasis, C. J. Matocha, J. Unrine, and Y. L. Thompson Copyright © 2014 J. L. Ghezzi et al. All rights reserved. Using Capacitance Sensors for the Continuous Measurement of the Water Content in the Litter Layer of Forest Soil Thu, 03 Apr 2014 07:34:18 +0000 Little is known about the wetting and drying processes of the litter layer ( layer), likely because of technical difficulties inherent in nondestructive water content (WC) monitoring. We developed a method for continuously measuring the WC of leaf litter (the “LWC method”) in situ using capacitance sensors. To test variants of this approach, five (for the LWC_5) or ten (for the LWC_10 method) Quercus serrata leaves were attached around capacitance sensors. The output voltage used for each LWC method was linearly correlated with the gravimetric WC (LWC_5: ; LWC_10: ), producing different slopes for each calibration line. For in situ continuous measurements of WC in the layer, two sensors were used, one placed on top of the layer and the other at the boundary between the and mineral layers. The average continuous WC of the layer was then calculated from the output voltage of the two sensors and the calibration function, and this value was linearly correlated with the gravimetric WC . However, because the layer characteristics (e.g., thickness, water-holding capacity, and species composition) may differ among study sites, appropriate approaches for measuring this layer’s moisture properties may be needed. Mioko Ataka, Yuji Kominami, Takafumi Miyama, Kenichi Yoshimura, Mayuko Jomura, and Makoto Tani Copyright © 2014 Mioko Ataka et al. All rights reserved. Soil Assessment along Toposequences in Rural Northern Nigeria: A Geomedical Approach Thu, 27 Mar 2014 11:29:06 +0000 Case numbers of endemic Ca-deficiency rickets (CDR) have been reported to be alarmingly rising among children of subsistence farms in developing countries within the last 30 years. Fluoride toxicities in the environment are known to not be related to the disease. To investigate if, instead, CDR is caused by a nutrient deficiency in the environment, subsistence farms in an endemic CDR area near Kaduna, northern Nigeria, were investigated for bedrock, slope forms, soil types, and soil characteristics. The natural environment was investigated according to the World Reference Base, soil texture was analysed by pipette and sieving, and plant-available macronutrients were determined using barium-chloride or Ca-acetate-lactate extraction. The analyses showed that granite and slope deposits were the dominant parent materials. The typical slope forms and soil types were Lixisols and Acrisols on pediments, Fluvisols in river valleys, and Plinthosols and Acrisols on plains. Compared with West African background values, all of the soils had normal soil textures but were low in macronutrients. Comparisons to critical limits, however, showed that only the P concentrations were critically low, which are typical for savanna soils. A link between nutrient deficiency in soils and CDR in the Kaduna area was therefore considered unlikely. Lena Hartmann, Marvin Gabriel, Yuanrong Zhou, Barbara Sponholz, and Heinrich Thiemeyer Copyright © 2014 Lena Hartmann et al. All rights reserved. Biosolids Soil Application: Agronomic and Environmental Implications 2013 Sun, 16 Mar 2014 09:38:53 +0000 Silvana I. Torri, Rodrigo Studart Corrêa, Giancarlo Renella, Leonid Perelomov, and Alejandro Valdecantos Copyright © 2014 Silvana I. Torri et al. All rights reserved. County-Scale Spatial Variability of Macronutrient Availability Ratios in Paddy Soils Tue, 11 Mar 2014 00:00:00 +0000 Macronutrients (N, P, and K) are essential to plants but also can be harmful to the environment when their available concentrations in soil are excessive. Availability ratios (available concentration/total concentration) of macronutrients may reflect their transforming potential between fixed and available forms in soil. Understanding their spatial distributions and impact factors can be, therefore, helpful to applying specific measures to modify the availability of macronutrients for agricultural and environmental management purposes. In this study, 636 topsoil samples (0–15 cm) were collected from paddy fields in Shayang County, Central China, for measuring soil properties. Factors influencing macronutrient availability ratios were investigated, and total and available concentrations of macronutrients were mapped using geostatistical method. Spatial distribution maps of macronutrient availability ratios were further derived. Results show that (1) availability of macronutrients is controlled by multiple factors, and (2) macronutrient availability ratios are spatially varied and may not always have spatial patterns identical to those of their corresponding total and available concentrations. These results are more useful than traditional soil macronutrient average content data for guiding site-specific field management for agricultural production and environmental protection. Mingkai Qu, Weidong Li, and Chuanrong Zhang Copyright © 2014 Mingkai Qu et al. All rights reserved. The Solid Phase Distribution and Bioaccessibility of Arsenic, Chromium, and Nickel in Natural Ironstone Soils in the UK Wed, 05 Mar 2014 13:31:23 +0000 Thirty soil samples (12 residential gardens and 18 allotments) were collected from the Cherwell District of north Oxfordshire in south-central England. The underlying parent geology of the area is dominated by Jurassic ironstone. The samples were analysed for their total contents of As, Cr, and Ni by X-ray fluorescence spectroscopy and for the bioaccessible fractions of these elements using a physiologically based extraction test. Four soils (two residential soils and two allotment soils) were chosen for further determination of their element solid phase distribution. The study showed that whilst total concentrations of As, Cr, and Ni are elevated due to the soil parent material, the bioaccessibility test showed that only a small proportion of the total concentration is available for absorption into the human body (<15%). The sequential extraction test showed that the nonmobile forms of the elements are strongly sorbed on to iron oxides. Parent material geology has a significant effect on the total element concentrations and the bioaccessibility of potentially harmful element (PHE). Land use does not show such a large effect but the allotment bioaccessibility data show a bigger spread and possibly higher values for As and Cr which may be due to agronomic (cultivation) practices such as addition of fertilisers and organic matter. Joanna Wragg, Mark Cave, and Sean Gregory Copyright © 2014 Joanna Wragg et al. All rights reserved. Soil Management for Sustainable Agriculture 2013 Wed, 26 Feb 2014 09:25:27 +0000 Philip J. White, John W. Crawford, María Cruz Díaz Álvarez, and Rosario García Moreno Copyright © 2014 Philip J. White et al. All rights reserved.