Showing papers in "Soil Science in 2013"
TL;DR: In this article, the adsorption-desorption behavior of phosphate on ferrihydrite, goethite, and hematite and underlying mechanisms were comparatively investigated with batch kinetics, solution equilibrium, and mineral characterization.
Abstract: The adsorption-desorption behavior of phosphate on ferrihydrite, goethite, and hematite and underlying mechanisms were comparatively investigated with batch kinetics, solution equilibrium, and mineral characterization. The phosphate adsorption kinetics for all Fe (hydr)oxides are described b
162 citations
TL;DR: In this article, the effect of Conocarpus biochar application on the hydraulic properties of a sandy loam soil was investigated in the context of soil properties and its efficiency as a long-term C sequester.
Abstract: Biochar research has received greater interest in recent years because of its potential beneficial effects on soil properties and its efficiency as a long-term C sequester. In this study, the effect of Conocarpus biochar application on the hydraulic properties of a sandy loam soil was invest
96 citations
TL;DR: Biochar addition to agricultural soil is reported in several studies to reduce climate gas emissions, boost carbon storage, and improve soil fertility and crop productivity as discussed by the authors, but knowledge of how biochar amendment affects soil physical changes is limited.
Abstract: Biochar addition to agricultural soil is reported in several studies to reduce climate gas emissions, boost carbon storage, and improve soil fertility and crop productivity. These effects may be partly related to soil physical changes resulting from biochar amendment, but knowledge of how bi
58 citations
TL;DR: Rice (Oryza sativa L.) is a semiaquatic plant produced globally as a staple food crop under flooded-soil conditions for the majority of the time it is actively growing.
Abstract: Rice (Oryza sativa L.) is a semiaquatic plant produced globally as a staple food crop under flooded-soil conditions for the majority of the time it is actively growing. Prolonged flooding results in the rapid depletion of oxygen and renders the soil highly anaerobic and reduced, both of whic
38 citations
TL;DR: In this paper, two data fusion methods (i.e., sample data fusion and sensor data fusion) were performed using a Fourier transform near-infrared (NIR) spectrometer and a portable X-ray fluorescence (PXRF) analyzer for predicting the contents of soil clay, silt, and sand in three sets of soil sample data, which were collected in a medium-scale area and two small-scale areas, respectively.
Abstract: Abstract Multiple proximal soil sensors provide more useful and complementary information than a single sensor does for improving the prediction of soil properties. In this study, two data fusion methods (i.e., sample data fusion and sensor data fusion) were performed using a Fourier transform near-infrared (NIR) spectrometer and a portable X-ray fluorescence (PXRF) analyzer for predicting the contents of soil clay, silt, and sand in three sets of soil sample data, which were collected in a medium-scale area and two small-scale areas, respectively. To verify the performance of these methods and confirm related theoretical analysis, calibration models on individual sample and sensor data sets, fused sample data sets, and fused sample and sensor data sets were constructed for three soil textural fractions. First, we applied stepwise multiple linear regression to PXRF measurements and partial least-squares regression to NIR spectral data in the three different sampling areas. Then, we used the sample data set from the medium-scale area as reference and combined it with other two sample data sets to calibrate the models. Finally, we further fused the principal components of NIR spectral data from principal component analysis with the PXRF measurements to improve the accuracy of soil texture prediction. It was found that the models based on fused data could significantly improve the accuracy of soil texture prediction compared with those based on individual sample or sensor data sets. The best model for the prediction of clay and sand contents was calibrated on fused PXRF measured data and NIR principal components from different sampling areas. Whereas geographical locations and soil types might impact the accuracy and fitness of the models, data fusion through multiple sensors and different sampling areas showed great promise as a technique for rapidly assessing soil textural fractions. Further evaluation of the data fusion methods suggested here may provide a practical technique for future applications in soil research.
38 citations
TL;DR: In this article, the authors evaluate Technosol and 'technogenic' qualifiers for other Reference Soil Groups, and propose new solutions which would improve the classification of technogenic soils in WRB.
Abstract: Technosols are relatively young soil group in WRB soil system, and there is still a lot of to do to better understand processes taking place in these soils and to classify them in a proper way. The objectives of this paper were to (1) evaluate Technosol and 'technogenic' qualifiers for other Reference Soil Groups, and (2) propose new solutions which would improve the classification of technogenic soils in WRB. New qualifiers n Edific, Nekric, Misceric, Artefactic, Radioactivic and new specifier n Technic n are proposed to be added to keys to Technosols. Moreover, Salic and Sodic qualifiers should be also available for Technosols. Further- more, the supplementation of definitions of thionic horizon and sulphidic material with reference to Technosols is also suggested.
37 citations
TL;DR: In this article, the potential of medical computed tomographic (CT) scanning for analyzing soil structure (macroporosity, soil matrix density, number of macropores) and how these estimates compare with, and complement, traditional laboratory measurements (bulk density, etc.).
Abstract: The aim of this study was to articulate the potential of medical computed tomographic (CT) scanning for analyzing soil structure (macroporosity, soil matrix density, number of macropores) and how these estimates compare with, and complement, traditional laboratory measurements (bulk density,
34 citations
TL;DR: In this article, the authors evaluated the contribution of roots in soil erosion control and the effect of root density in soil erodibility and soil physical properties, and found a positive correlation between soil shear strength and root density, but no influence of roots on bulk density and saturated hydraulic conductivity.
Abstract: Although both aboveground and belowground components of vegetation act together in reducing soil erosion, mainly the aboveground component has received attention in past research. The aim of this study was to evaluate the contribution of roots in soil erosion control and the effect of root density in soil erodibility and soil physical properties. Perennial ryegrass (Lolium perenne L. Hugo) was grown in soil pans, and laboratory rainfall simulation experiments were conducted after 4, 8, 12 weeks of their growth with seeding density of 50 kg ha-1, after 4 weeks for seeding density of 100 kg ha-1, and on a control. The experiments with ryegrass were done in the presence of complete plants and after clipping off the shoots. Roots of ryegrass grew rapidly, attaining densities of 0.614 kg m-2 and 2.280 kg m-2 in 4 and 12 weeks, respectively. With increasing root density, splash and wash decreased exponentially. There was positive correlation between soil shear strength and root density, but no influence of roots on bulk density and saturated hydraulic conductivity was observed.
32 citations
TL;DR: In this paper, the authors evaluated chronosequence effects on restoration quality indicators in reclaimed coal mine soil from different land use landscapes and agroecosystems in Mississippi, and found that reclamation practices improved soil quality over time.
Abstract: Abstract Surface mining drastically disturbs landscapes and soil properties. Reclamation can restore and improve soil quality and biomass productivity. Time required for soil reclamation to restore soil quality to premined conditions in southeastern United States is unclear. The objective of this study was to evaluate chronosequence effects on restoration quality indicators in reclaimed coal mine soil from different land use landscapes and agroecosystems in Mississippi. Study sites in 0‐ to 3‐, 5‐ to 7‐, and 10‐ to 12‐year‐old reclaimed soils were compared with adjacent undisturbed sites. Soil samples collected at the 0‐ to 15‐cm and the 15‐ to 30‐cm depths within a grid in a radius of 3 m were mixed to produce composite samples and kept frozen until analyzed. Soil bulk density (&rgr;b) was the highest (1.48 g cm−3) in the youngest (< 1 year) site and decreased with increasing age to the oldest (12‐year) site (1.07 g cm−3). Soil quality indicators (aggregate stability, total C, organic C, and microbial biomass C) increased with increasing reclamation age in forest and grass ecosystems. Concentrations of C were greater at the summit than at shoulder and foot‐slope positions. Soil pH, Ca, Mg, Cu, and Zn were higher in newly reclaimed soil than in soils reclaimed 12 years earlier possibly because of reclamation liming practices, which buffer pH to greater than 7.0 in newly reclaimed sites. Reclamation practices improved soil quality over time. Soil quality indicators reached levels similar to those of undisturbed soil within 7 to 12 years after reclamation, indicating successful reestablishment of healthy and sustainable soils in the postmining ecosystems.
31 citations
TL;DR: In this article, the suitability of LDM as a routine method for determining soil PSD, evaluate the precision or its repeatability of PSD parameters, and establish a simplified protocol for transforming the LDM results into SPM ones.
Abstract: Laser diffraction method (LDM) provides a rapid solution for obtaining soil particle size distribution (PSD) especially in the anal- ysis of a larger number of soil samples. However, there are disadvan- tages associated with the use of LDM for PSD measurements over the traditional sieve-pipette method (SPM). The present study is aimed to assess the suitability of LDM as a routine method for determining soil PSD, evaluate the precision or its repeatability of PSD parameters, and establish a simplified protocol for transforming the LDM results into SPM ones. The soil samples (n = 43) from 13 Chinese provinces were analyzed, and the results indicated that the relative errors for clay, silt, and sand fractions by the LDM were 35.34, 27.38, and 19.41%, respec- tively, compared with those by the SPM in the condition of limited sam- ple numbers and large between-sample variation; samples could best be run at least twice during the LDM analysis to reduce the error caused by a limited sample volume; and a soil particle refractive index of 1.50 and a soil particle absorption index of 0.01 were found to be optimal for the Mie theory model. With relatively limited sample numbers and apparent textural difference between the samples, the distinct incompatibilities were observed in the present work between the PSD obtained by the LDM and SPM. However, depending on the specific research purpose, the deviations between the LDM and SPM may be considerably reduced with an increase in the sample capacity or a decrease in the spatial scale.
28 citations
TL;DR: In this article, a new index of pore connectivity based on water flux, Cw, was developed as a ratio between K and pore volume for each pore size class.
Abstract: No-tillage (NT) systems have been increasing during the last several decades. Development of a near-surface layer of laminar structure under NT has also been reported. The objectives of this work were to determine whether preferential connectivity of different pore size classes in two differently textured soils under NT exists and to propose a new index of pore connectivity based on water flux (Cw). The study was carried out at two sites in the Pampas Region of Argentina under long-term NT. Site 1 had a loamy A-horizon, and Site 2 had a sandy loam A-horizon. Undisturbed samples were extracted in vertical and horizontal directions within the first 8 cm of the soil. Saturated hydraulic conductivity (K s), near-saturated hydraulic conductivity (h: −50, −100, −200, −300, and −500 cm), pore size distribution from water retention curve, and total porosity were determined. The index of pore connectivity based on water flux, Cw, was developed as a ratio between K and pore volume for each pore size class. Site 1 showed laminar structure in the A-horizon, whereas Site 2 showed a blocky structure. We found a preferential connectivity in horizontal direction of macropores in Site 1. The index of pore connectivity was useful to assess the presence of preferential orientation of different pore size classes. In future studies, the connectivity of the different pore size classes should not be neglected.
TL;DR: In this paper, the authors used repacked lysimeters with 90 cm height and 25 cm inner diameter for comprehensively determining ammonia (NH3) and nitrousoxide (N2O) emissions and N leachinglosses in a rice-wheat cropping system irrigated with N-rich wastewater from a live stock pond.
Abstract: Sewage effluents are increasingly used for farmland irrigation worldwide. This practice makes N losses via gaseous forms and leaching process more complex. Twelve repacked lysimeters with 90 cm height and 25 cm inner diameter were used for comprehensively determining am- monia (NH3) and nitrousoxide(N2O) emissionsand N leachinglossesina rice-wheat cropping system irrigated with N-rich wastewater from a live- stock pond. There were four irrigation treatments with three replications: wastewater with high N concentration (HW), wastewater with medium N concentration (MW, one-half dilution of wastewater of HW), wastewater with low N concentration (LW, one-fourth dilution of wastewater of HW), and ultrapure water control (CK). All treatments received equal amounts of total N (225 kg N ha �1 in the riceseasonand 150kgNha �1 in thewheat season) by balancing with commercial N fertilizer. The wastewater was provento be as effective ascommercialN fertilizer to achieve the optimum crop yields when applied in an appropriate amount. The NH3 emission, N leaching, and N2O emission losses accounted for 16.2 to 19.8%, 4.6 to 6.4%, and 0.26 to 0.35% of the total N applied in the rice season, respec- tively, whereas they were 2.7 to 3.3%, 2.2 to 2.8%, and 0.77 to 1.0% in the wheat season. Irrigating with wastewater did not change the NH3 emission flux pattern after N fertilizer (urea) was applied, but it boosted the NH3 emission flux to a certain extent in the rice season, especially for the MW treatment, which was mainly attributed to the high ammonium con- tent and pH of the flood surface water resulting from a combined effect of wastewater and urea-N application. In addition, N-rich wastewater irri- gation did not significantly increase N2O emission and N leaching when the total N inputs and the amount of irrigation were the same.
TL;DR: In this article, a strong linear relationship was found between gas transport parameters and soil-pore geometry revealed by X-ray CT, indicating that gas dispersivity has a linear and inverse relationship with gas diffusivity.
Abstract: Gas transport parameters and X-ray computed tomography (CT) measurements in porous medium under controlled and identical conditions provide a useful methodology for studying the relationships among them, ultimately leading to a better understanding of subsurface gaseous transport and other soil physical processes. The objective of this study was to characterize the relationships between gas transport parameters and soil-pore geometry revealed by X-ray CT. Sands of different shapes with a mean particle diameter (d 50) ranging from 0.19 to 1.51 mm were used as porous media under both air-dried and partially saturated conditions. Gas transport parameters including gas dispersivity (α), diffusivity (D P/D 0), and permeability (k a) were measured using a unified measurement system (UMS). The 3DMA-Rock computational package was used for analysis of three-dimensional CT data. A strong linear relationship was found between α and tortuosity calculated from gas transport parameters (
), indicating that gas dispersivity has a linear and inverse relationship with gas diffusivity. A linear relationship was also found between k a and d 50/T UMS 2, indicating a strong dependency of k a on mean particle size and direct correlation with gas diffusivity. Tortuosity (T MFX) and equivalent pore diameter (d eq.MFX) analyzed from microfocus X-ray CT increased linearly with increasing d50 for both Granusil and Accusand and further showing no effect of particle shape. The T UMS values showed reasonably good agreement with T MFX values. The k a showed a strong relationship when plotted against d eq.MFX/T MFX 2, indicating its strong dependency on pore size distribution and tortuosity of pore space.
TL;DR: In this article, different prediction techniques are available to assess and map spatial variability of soil properties, but selecting the most suitable one is not the most appropriate for agricultural and environmental use.
Abstract: Information on the spatial variability of soil texture including soil clay content in a landscape is very important for agricultural and environmental use. Different prediction techniques are available to assess and map spatial variability of soil properties, but selecting the most suitable
TL;DR: In this article, the effects of inorganic and organic fertilizer treatments (control, chemical fertilizer, animal manure, compost, and compost + mycorrhizal inoculation) on bulk density (ρ b ), C and N concentrations, soil organic C (SOC) pool, C sequestration, total N, aggregate fractions, water-stable aggregates (WSA), and mean weight diameter (MWD) in the long-term field experiment initiated in 1996 on the Mediterranean coast of Turkey.
Abstract: Soil management practices significantly impact soil aggregation and carbon (C) dynamics. Organic fertilizer and mycorrhizal inoculation also affect aggregate stability and soil C pool. Thus, this study was designed to assess the effects of inorganic and organic fertilizer treatments (control, chemical fertilizer, animal manure, compost, and compost + mycorrhizal inoculation) on bulk density (ρ b ), C and N concentrations, soil organic C (SOC) pool, C sequestration, total N, aggregate fractions, water-stable aggregates (WSA), and mean weight diameter (MWD) in the long-term field experiment initiated in 1996 on the Mediterranean coast of Turkey. Disturbed and undisturbed soil samples were collected from the 0- to 0.15-m and 0.15- to 0.30-m depths after wheat (Triticum aestivum) harvest in June 2010 to determine the soil physical and chemical characteristics. Soils that received animal manure, compost, and compost + mycorrhizae contained more C (in percent), N (in percent), SOC, and total N concentrations than control. In comparison with control, chemical fertilizers also affected soil C and N concentrations and pools by increasing plant biomass production. The C/N ratio of soil was less than 10 in control and chemical fertilizer treatments but more than 10 in animal manure, compost, and compost + mycorrhizae treatments. Organic fertilizers significantly reduced ρ b and increased porosity (in percent). Total amounts and rate of C and N sequestration increased with application of organic fertilizers. The rate (kg C ha ―1 year ―1 ) of C sequestration in 0- to 0.15-m depth was 7.19 for control, 329.6 for animal manure, and 273.4 for the compost + mycorrhizae treatment. Furthermore, organic fertilizers significantly increased the SOC concentrations in different aggregate size fractions. The C and N concentrations in the 0.25- to 1.0-mm aggregate size were higher than those in the less than 0.25-mm fraction. Concentrations of C and N decreased significantly with the decrease in aggregate size less than 0.25 mm (P < 0.0009). Application of organic fertilizers impacted soil ρ b , WSA, and MWD. Compost + mycorrhizae―treated soil had the highest MWD (3.09 mm), and the control treatment had the least (1.49 mm). Decline in aggregate size decreased WSA in compost and mycorrhizae treatments. The high values of MWD were associated with mycorrhizal inoculation rather than with application of organic fertilizer. Application of organic fertilizers including mycorrhizal inoculation contributed considerably to soil aggregation and soil C sequestration. There was more C concentration in 1- to 2-mm and 0.5- to 1-mm aggregate sizes than in the less than 0.25-mm size range. Additional research is needed to assess the role of mycorrhizae on macroaggregate development and C sequestration under long-term soil and crop management systems.
TL;DR: In a 120-year old beech (Fagus sylvatica L) stand located in Middle Pomerania, Germany, the authors of as discussed by the authors found that leaves were the major component of plant litterfall and their contribution was 82.4n84.5% in the non-seed years and 47.2% during the seed year.
Abstract: Studies of plant litterfall mass, its dynamics, structure and chemical composition were conducted between 2007n2010 in a 120-year old beech (Fagus sylvatica L.) stand located in Middle Pomerania. The annual mass of litterfall during the study period ranged from 2.793 to 5.398 tha n1 and its maximum was observed during the seed year. Leaves were the major component of plant litterfall and their contribution was 82.4n84.5% in the non-seed years and 47.2% during the seed year. Inflorescences, seeds, and seed coats were important components of litterfall during the seed year and accounted together up to 39.8% of the total litterfall mass. Particular fractions of litterfall significantly differed in the chemical composition. The highest concentrations of nitrogen, phospho- rus and potassium were noticed in seeds and leaves collected in spring and the maximum content of calcium was observed in leaves collected in autumn. The weighted mean annual concentrations of nitrogen ranged within 0.81n1.13%, phosphate n 0.126n0.153%, potassium n 0.298n0.485% and calcium n 0.416n0.583%. The influx of elements with litterfall to the soil was: 167.3n225.9 kgha n1 of ash, 23.2n61.0 kgha n1 of nitrogen, 3.6n7.6 kgha n1 of phosphorus, 8.3n26.2 kgha n1 of potassium and 15.3n22.4 kgha n1 of calcium.
TL;DR: In this article, the authors make a comparative study of the effects of organic materials with different degrees of stabilization and source (an untreated pig slurry, the solid fraction of the digestate from the anaerobic fermentation of pig wastes, a livestock-derived organic matter compost, and an urban waste compost) on the size, activity, and structure of the microbial community in two arable soils.
Abstract: Abstract Although the application of organic amendments to arable soils is considered to be a suitable tool for improving soil fertility and enhancing carbon (C) stocks, more research is required on the influence of input of organic matter on the activity and structure of the soil’s microbial community. The aim of this work was therefore to make a comparative study of the effects of organic materials with different degrees of stabilization and source (an untreated pig slurry, the solid fraction of the digestate from the anaerobic fermentation of pig wastes, a livestock-derived organic matter compost, and an urban waste compost) on the size, activity, and structure of the microbial community in two arable soils. These effects, studied through a laboratory incubation experiment, were related to the quantity and quality of organic matter added, as well as to the rapid changes in the more labile water-soluble organic matter fraction. Particular attention was devoted to the short-term variations after organic amendment, during which changes in CO2 emissions, microbial biomass C, and water-extractable organic C pools were most pronounced. Phospholipid fatty acid profiles and 16S rDNA sequence analyses evidenced changes in the microbial community structure of amended soils. Modifications of the structure of bacterial communities after amendment, generally involving declining proportions of Gram-positive bacteria (Actinobacteria and Firmicutes) and an increase in abundance of Gram-negative bacteria (Acidobacteria, Bacteriodetes, and Proteobacteria), were both quality and quantity dependent, with effects being proportional to the mineralizable organic C content of the added materials.
TL;DR: In this article, the authors examined the use of visible near-infrared spectroscopy (Vis-NIR) as a speedy method to predict soil organic carbon (SOC) and to monitor spatial and temporal changes in SOC compared with labor-intensive traditional laboratory (TL) measurements.
Abstract: Monitoring the spatial and temporal changes in soil organic carbon (SOC) brought about by climate change and agricultural practices is challenging because existing SOC monitoring methods are very time and resource consuming. This study examined the use of visible near-infrared spectroscopy (Vis-NIR) as a speedy method to predict SOC and to monitor spatial and temporal changes in SOC compared with labor-intensive traditional laboratory (TL) measurements. For SOC prediction, topsoil (0–25 cm) and subsoil (25–50 cm) samples in the Danish soil spectral library for the years 1986 and 2009 were used. Empirical Bayesian Kriging was used to map SOC. The Vis-NIR predictions indicated that average topsoil and subsoil SOC had decreased slightly in Denmark from 1986 to 2009, and this was confirmed by TL measurements of SOC. In East Denmark, Vis-NIR predictions differed significantly from the measured SOC values. For subsoil samples, the ability of Vis-NIR to predict SOC levels varied. In West Jutland, Central Jutland, North Jutland, and Thy, Vis-NIR–predicted SOC levels did not differ from TL-measured levels, showing good predictive ability. For topsoil samples, the spatial pattern of change in TL-measured and predicted SOC was consistent during the 23-year study period, but there were significant discrepancies in the corresponding SOC change patterns for subsoil samples. To conclude, Vis-NIR is a promising method for monitoring spatial and temporal changes in SOC at the national scale, especially in the topsoil. Some difficulties can arise in low SOC subsoils, so more systematic work is needed to improve the method for practical applications.
TL;DR: In this article, the content, distribution and mobility of barium and strontium in various forest podzol soils were determined using the five-step procedure of Tessier et al. (1979).
Abstract: Abstract The study was aimed at determining the content, distribution and mobility of barium and strontium in various forest podzol soils. Samples with a wide range of chemical and physical properties were collected from typical uncontaminated soils of south-western Poland. The total metal content in the analyzed soils was considered as the geochemical background thanks to the natural features of the study site. Sequential chemical extraction procedure were used to provide information on the mobility and bioavailability of the studied metals in the soil. Fractions of Ba and Sr were determined using the five-step procedure of Tessier et al. (1979). The results show that heavy metals were generally represented by the exchangeable fraction (F1 . barium) and the residual fraction (F5 . strontium) with the average values at 53 and 69%, respectively. The mobility of barium in all soil profiles was very high, ranging within 52.54% and indicating a generally high availability and mobility. Relatively very low levels of the trace elements were found in the fraction bound to organic matter (F4: 3.8%). Very low levels of strontium were found also in the fraction bound to carbonates (F2: 2.3%). Humic-eluvial, illuvial and sideric horizons were enriched in the fractions of barium and strontium bound to iron and manganese oxides (F3).
TL;DR: In this article, a total of 537 soil samples were collected based on a 30 × 30-m grid from a permanent dairy farm in southeastern Ireland, and five different subsample experiments at lower densities based on the original data set were performed to study the optimal soil sampling design for soil P and Mg using geostatistics and a GIS (geographical information system).
Abstract: Soil sampling design is an important issue for agricultural management and environmental monitoring. In this study, a total of 537 soil samples were collected based on a 30 × 30–m grid from a permanent dairy farm in southeastern Ireland. Five different subsample experiments at lower densities based on the original data set were performed to study the optimal soil sampling design for soil P and Mg using geostatistics and a GIS (geographical information system). Soil P ranged from 1.3 to 35.7 mg L, with a CV value of 0.68. Soil Mg ranged from 134.7 to 685.2 mg L, with a small CV value of 0.28. Soil P followed neither a normal nor a lognormal distribution. Box-Cox transformation was applied to achieve normality. On the other hand, soil Mg followed a normal distribution, as did its subdata. For soil P, an omnidirectional spherical model was used to describe the spatial autocorrelation. For soil Mg, a nested model (an exponential model combined with a Gaussian model) was used to fit the variograms. Further soil P interpolated maps revealed that soil grid sampling interval could increase to 90 m without a significant loss of spatial information, whereas soil Mg sampling interval could increase to 120 m, confirming that soil Mg had much stronger spatial structure than soil P. According to this study, a grid of 90 × 90 m was recommended for soil sampling, which was confirmed in other practical grassland farms. The spatial structure information was very useful to optimize soil sampling design for practical grassland management.
TL;DR: In this paper, the authors proposed a method to prevent nonphysical combinations of soil hydraulic parameter sets obtained by optimization by adopting the soil hydraulic analytical model by Kosugi because it enables the feasible parameter space to be reduced by predicting parameter σ from Rm, which are the variance and mean of the log-transformed soil pore-dius, respectively.
Abstract: Effective soil hydraulic parameters of soil vegetation atmo- sphere transfer (SVAT) models can be derived in a cost-efficient way by inverse modeling. Nevertheless, a serious drawback of SVAT models based on Richards' equation is that they require as many as five unex- ploited correlated hydraulic parameters. To reduce the feasible parame- ter space, we propose a method to prevent nonphysical combinations of soil hydraulic parameter sets obtained by optimization. We adopt the soil hydraulic analytical model by Kosugi because it enables the feasible parameter space to be reduced by predicting parameter σ from Rm, which are the variance and mean of the log-transformed soil pore ra- dius, respectively. To further decrease the parameter space, we derive two models to predict saturated hydraulic conductivity, Ks, from three or four Kosugi soil water retention parameters, respectively. These two models are based on the combination of the Hagen-Poiseuille and Darcy equations that use three semiempirical parameters (τ1, τ2, and τ3) cali- brated on large UNSODA and HYPRES databases. Our derived models are compared with a version of the Mishra and Parker (1990. Ground Water. 28:775-777) Ks model being modified to account for the pa- rameters of Kosugi's relationships. The results show that the uncertain- ties of the developed Ks model are comparable to the uncertainties of Ks measurements. Moreover, the developed Ks model outperforms the Mishra and Parker model. Therefore, the developed method will enable one to substantially reduce the feasible range of the inverted Kosugi's hydraulic parameters.
TL;DR: In this paper, the authors used flow calorimetry to compare and better understand sulfate and phosphate sorption and sorption mechanisms on amorphous aluminum hydroxide (AHO).
Abstract: The fate and transport of sulfate and phosphate in the environment are largely mediated by how these anions react with soil colloids, especially metal (hydr)oxides. The overall objective of this study was to use flow calorimetry to compare and better understand sulfate and phosphate sorption and sorption mechanisms on amorphous aluminum hydroxide (AHO). This was performed by measuring the in situ heats of NO3 and Cl and K and Na exchange before and after reaction of AHO with sulfate and phosphate, by measuring heats of sulfate and phosphate sorption on AHO, and by determination of the amount of sulfate and phosphate sorbed. The AHO used in our study was synthesized in-house and was amorphous. All solutions used in our experiments had pH of 5.8 and ionic strengths of 50 mmol/L. Sulfate and phosphate treatment of the AHO reduced anion exchange by 61% and 77%, respectively, relative to the measured heats of NO3 and Cl exchange before SO4 or H2PO4 treatment. Sulfate and phosphate treatment of the AHO did not change measured heats of K and Na exchange. The molar heats of sorption were 2.9 ± 1.4 kJ/mol for sulfate and − 6.5 ± 3 kJ/mol for phosphate. The thermodynamic exchange (NO3 and Cl and K and Na) and sorption (SO4 and H2PO4) data obtained by the flow calorimeter differentiated between outer- and inner-sphere SO4 and H2PO4 sorption mechanisms in situ and indicated that these ligands irreversibly sorbed on AHO by most likely forming monodentate complexes, bidentate bridging complexes, and Al-hydroxy surface precipitates.
TL;DR: In this article, a method for assessing available soil Ca does not fully characterize soil Ca forms, and it has been hypo-hypo to account for discrepancies in ecosystem Ca budgets.
Abstract: Acid deposition and repeated biomass harvest have decreased soil calcium (Ca) availability in many temperate forests worldwide, yet existing methods for assessing available soil Ca do not fully characterize soil Ca forms. To account for discrepancies in ecosystem Ca budgets, it has been hypo
TL;DR: In this article, multivariate empirical mode decomposition (MEMD) was applied to reveal the multiscale influences of soil properties on SWC distribution in the Loess Plateau landscapes.
Abstract: The characterization of hydrological and biological processes requires information on the scaling properties of soil water content (SWC). In this regard, accurate estimation of nonstationary and nonlinear SWC distribution for various scales is a challenge. In this study, multivariate empirical mode decomposition (MEMD) was applied to reveal the multiscale influences of soil properties on SWC distribution in the Loess Plateau landscapes. Seven data sets analyzed in this study were SWC of 0 to 100 cm measured at seven different periods from two transects with obvious differences in five soil properties, that is, soil organic matter, clay, silt, sand, and bulk density. Soil water content and soil properties were separated into different numbers (four in Transect 1 and three in Transect 2) of intrinsic mode functions (IMF) and residue representing different "common" scales by MEMD. Scale-specific relationships between SWC and soil properties varied with scales and measurement periods. The influence of soil properties on SWC was more deterministic at greater scales. Soil water content at each IMF (specific scale) or residue was predicted from the scale-specific controlling factors and the summing up of all the predicted IMF, and residue simulated well the SWC distribution at the measurement scale. Soil organic matter and soil particle composition were the main explanatory variables for the overall SWC estimation, respectively, for the two transects. The overall SWC prediction using MEMD outperformed the SWC predictions using the traditional method based on the original data.
TL;DR: In this paper, the authors identify the variations in physical, chemical, and mineralogical composition of soils of the region lying between the southern part of Zagros and Persian Gulf to Oman Sea.
Abstract: There are relatively few comprehensive documents about the mineralogy of arid regions, and no study has been reported on the characteristics and mineralogical trends of the soils of arid regions in the Hormozgan Province, southern Iran. The objective of this study was to identify the variations in physical, chemical, and mineralogical composition of soils of the region lying between the southern part of Zagros and Persian Gulf to Oman Sea. X-ray diffraction, thin-section studies, and transmission electron microscopy with energy-dispersive X-ray spectroscopy were conducted to determine the relationship between mineral distribution and climate, along with an evaporate environment reflected by a variety of geological structures. On the basis of nature and composition, the soils can be classified into Alluvial soils rich in silt and Desert soils, sandy soils poor in organic carbon in which evaporate Tertiary Formations played an important role on the formation of contemporary minerals. The maximum portions of silt and sand fraction were composed of quartz and alkali-feldspars, whereas calcite and dolomite were elevated in soil samples without acid treatments. The clay mineralogy results revealed that detrital input and inheritance are possibly the main source of kaolinite, smectite, chlorite, and illite, whereas in situ neoformation during the Tertiary shallow saline and alkaline environment could be the dominant cause of palygorskite occurrences in the sedimentary rocks. The chemical composition of clay suspension, determined by electron microprobe analysis, corresponds to that of Mg-rich predominant palygorskite, with a degree of tetrahedral substitution from almost less than 2 to 23%. In conclusion, the soil mineralogy did not vary systematically with depth but showed spatial variations, and the relative influence of mineral distribution in topsoils can be summarized as follows: parent rocks > geomorphological setting > water table position > climate > physiography and soil evolution. The soils, in general, contained moderate to high amounts of weatherable minerals, indicating their early to intermediate stages of development.
TL;DR: In this article, B. tectorum invasion and elevated bioturbation have potential long-term ramifications to soil pedogenesis and plant successional trajectories, as well as changes in surface soil properties induced by both invasion-fostered increase in mice and rodents.
Abstract: Abstract Bromus tectorum (cheatgrass) has replaced native Artemisia (sagebrush)/bunchgrass communities throughout the Intermountain West. Using the framework of Jenny (1941), we hypothesized that invasion by B. tectorum could alter pedogenic trajectories. Hypothesis testing involved monitoring the invasion of a Krascheninnikovia lanata (winterfat) community by B. tectorum. In 1999, 13 points were established, 50 m apart, extending from the invasion front to noninvaded areas. For more than 11 years, soils were sampled randomly near each point, 0 to 20 cm, and analyzed for various soil attributes. Using autoregression, trends with time between invaded and noninvaded soils differed significantly (P ⩽ 0.05) in solution-phase ortho-P and Ca + 2, phosphatase activities, and net 30-day N mineralization potentials. Notable trends with time, regardless of invasion status, included a decline in solution-phase Mg + 2 and K + and an increase in soil pH and the molar proportion of NH4 + in the mineral N fraction. Relative to noninvaded soils, B. tectorum soils had greater mineral N and greater molar proportion of NH4 + in that fraction; greater amidase and phosphatase activities; greater solution-phase ortho-P and molar proportion of NO2− in the NO2−−N + NO3−−N pool; greater micronutrient availability of Fe and Cu; and higher soil pH. The decline in solution-phase Ca + 2 and ortho-P and the increase in soil pH are likely caused by an invasion-fostered increase in bioturbation from rodents, which mixes carbonate-bearing soil from lower horizons to the soil surface. Changes in surface soil properties induced by both B. tectorum invasion and elevated bioturbation have potential long-term ramifications to soil pedogenesis and plant successional trajectories.
TL;DR: In this paper, the sorption and desorption characteristics of lowland peaty clay soils are described based on experimental laboratory studies, and the maximum P sorption capacity is comparable to that of acid sandy soils if based on the amount of oxalate-extractable aluminum and iron.
Abstract: To determine phosphorus (P) losses from agricultural land to surface water, information is needed about the behavior of P in soils. In this study, the sorption and desorption characteristics of lowland peaty clay soils are described based on experimental laboratory studies. The maximum P sorption capacity is comparable to that of acid sandy soils if based on the amount of oxalate-extractable aluminum and iron. A fraction of the maximum amount of sorbed P is bound reversibly (Q), which can be measured with an iron-impregnated paper. The fraction of the maximum reversibly sorbed P depends on the amount of oxalate-extractable aluminum and iron. In the topsoil, the maximum of the fraction of reversibly bound P (Qm) is about one third of maximum P sorption capacity; and in the subsoil, about two thirds. All sorption and desorption parameters are related to soil characteristics of peat samples.
TL;DR: In this article, the authors investigated the mineral properties and OM stabilization in 12 surface tropical soil samples and found that stable carbon (stable C) was primarily preserved in silt and clay fractions.
Abstract: Abstract The association of organic matter (OM) with minerals in soils that leads to the stabilization of OM has been linked to specific surface area (SSA) and mineralogy. This study investigated the mineral properties and OM stabilization in 12 surface tropical soil samples. The results showed that stable carbon (stable C) was primarily preserved in silt and clay fractions. The clay fraction was mainly composed of kaolinite, with minor amounts of hematite. The SSA was highly correlated with both crystalline and poorly crystalline Fe oxides and clay content, but there was low correlation with stable and labile carbon. The correlation between SSA and Fe oxides was stronger with crystalline than with poorly crystalline minerals and clay. In general, the SSA of soils increased after removal of organic carbon. However, some samples, especially in the clay fraction, showed a decrease in SSA after removal of organic carbon because of the effect of coating or precipitation of OM on the weakly crystalline Fe oxides.
TL;DR: In this article, a brown coal preparation (Rekulter) was applied as the source of organic matter in autumn 1999 to the studied soil, which was contaminated with cadmium, lead and zinc.
Abstract: Organic matter takes part in all soil processes and influences the physical, chemical and biological properties of soil. The paper presents the analysis of heavy metal contents (Zn, Pb, Cd) in soil and biomass of darnel multifloral (Lolium multiflorum Lam.) cultivated at diverse conditions of soil reaction and organic matter content. A brown coal preparation (Rekulter) was applied as the source of organic matter in autumn 1999 to the studied soil, which was contaminated with cadmium, lead and zinc. The limiting influence of Rekulter on the uptake of heavy metals by darnel multifloral (two cuts of the test plant) was the highest in the case when the largest dose was applied to soil with the highest pH (about 6.0). Bioaccumulation indexes (BI) for Cd, Pb, Zn indicate the mobility and bioavailability of Cd, Pb and Zn in soils. The BI for particular heavy metals were generally low, with the lowest in the case when the largest dose of Rekulter was applied to all cuts of the test plant
TL;DR: In this paper, the impact of soil management practices on phosphorus (P) forms and lability in Alabama Decatur silt loam cropped with cotton was assessed and the data indicated that inorganic P in the soils studied was mainly associated with Fe and Al oxides and was not readily bioavailable.
Abstract: Abstract Alabama is a major cotton production state in the USA. In this study, we assessed the impact of soil management practices on phosphorus (P) forms and lability in Alabama Decatur silt loam cropped with cotton. The data indicated that inorganic P in the soils studied was mainly associated with Fe and Al oxides and was not readily bioavailable. On the other hand, elevated levels of water plus Fe and Al inorganic P fractions were observed in soils treated with poultry litter compared to the control and other inorganic fertilized soils. Most of the soil organic P was associated with Al oxide (> 40%) with the exception of the no-till and control treatments where the bulk of the soil organic P was organic matter bound. Water soluble organic P increased after poultry litter applications whereas no increase was observed with inorganic fertilization. Statistical analysis (mean separation) revealed that the phosphatase and phytase hydrolyzed water soluble organic P within each treatment was not significantly different at P < 0.05. More than 50% of organic P in the sequentially-extracted NaOH fraction was hydrolyzable by the various phosphatase enzymes, indicating that NaOH-extractable organic P is labile. Any portion of the organic P extracted in the fractions that was not hydrolyzed by the enzymes is considered to be in the complex forms tightly bound to colloidal and other materials.