bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil Mapping Using GIS, Expert Knowledge, and Fuzzy Logic
Authors: Zhu A. X. , Hudson B. , Burt J. , Lubich K. , Simonson D.
Published: July 2010

A geographical information system (GIS) or expert knowledge‐based fuzzy soil inference scheme (soil‐land inference model, SoLIM) is described. The scheme consists of three major components: (i) a model employing a similarity representation of soils, (ii) a set of inference techniques for deriving the similarity representation, and (iii) use of the similarity representation. The similarity representation allows the soil landscape to be considered as a continuum, and thereby overcomes the generalization of soils in conventional soil mapping. The set of inference techniques is based on the soil factor equation and the soil–landscape model. The soil–landscape concept contends that if one knows the relationships between each soil and its environment for an area, then one is able to infer what soil might be at each location on the landscape by assessing the environmental conditions at that point. Under the SoLIM, soil environmental conditions over an area are characterized using GIS or remote sensing techniques. The relationships between soils and their formative environmental conditions are extracted from local soil experts or from field observations using a set of artificial intelligence techniques. The characterized environmental conditions are then combined with the extracted relationships to derive a similarity representation of soils over an area. It is demonstrated through two case studies that the SoLIM for soil survey has many advantages over the conventional soil survey approach. Soil information products derived through the SoLIM are of high quality in terms of both level of spatial detail and degree of attribute accuracy. In addition, the scheme shows promise for improving the efficiency of soil survey and subsequent updates through reducing time and costs of conducting a survey. However, the degree of success of the SoLIM highly depends on the availability and quality of environmental data, and the quality of knowledge on soil–environmental relationships over the study area.
Potential use of Rare Earth Oxides as Tracers for Soil Erosion and Aggregation Studies
Authors: Zhang X. C. , Friedrich J. M. , Nearing M. A. , Norton L. D.
Published: July 2010

Most existing soil loss data are spatially‐averaged, though various tracing techniques have been used for obtaining spatially‐distributed data. Spatially‐distributed soil erosion data are needed for validating physically‐based erosion prediction models and for better understanding soil erosion dynamics. The objectives of this study were to evaluate the feasibility of using rare earth element (REE) oxides directly as tracers for soil erosion studies by examining their binding ability with soil materials, and also to test a quick acid‐extraction procedure. Five REE oxide powders were directly mixed with a Miami silt loam soil (fine‐loamy, mixed, mesic Typic Hapludalfs) and then leached with deionized water in a soil box to evaluate the mobility of REEs. Following leaching, soil samples were sectioned in 25‐mm increments and analyzed for REEs. The REE‐tagged soil was wet sieved to obtain REE concentrations in each aggregate size group. A simple acid‐leaching method was used to extract REEs from all soil samples. The extracts were analyzed by Inductively Coupled Plasma‐Mass Spectrometry (ICP‐MS) techniques. The data indicated that the maximum coefficient of variation of the proposed procedure was <10% for all REEs. The REE oxides were uniformly incorporated into soil aggregates of different sizes (>53 μm) and were bound with silt‐size particles. This finding shows that the direct use of REE oxides is feasible, which should be superior to other REE‐tagged particulate tracers because it eliminates the need of tagging exotic particles with REEs. Also, direct mixing of a trace amount of REEs does not substantially alter physicochemical properties of soil particles and aggregates. This work has shown that REE oxides have a great potential for tracing soil erosion and aggregation.
Carbon and Nitrogen Dynamics in Preferential Flow Paths and Matrix of a Forest Soil
Authors: Bundt Maya , Jäggi Maya , Blaser Peter , Siegwolf Rolf , Hagedorn Frank
Published: July 2010

Natural abundance (δ) of the stable isotopes 13C and 15N has gained acceptance for studying C and N cycling in forests. In most studies, bulk soil samples are collected to determine isotope abundance. Such sampling overlooks the potential impact of preferential flow on isotope distribution. The objective of this study was to investigate the effects of preferential flow on the distribution of soil organic carbon (SOC), total N, δ13C, and δ15N in a forest soil in Central Switzerland. Preferential flow paths in the soil were identified with a dye tracer, Brilliant Blue (Plüss‐Staufer AG, Oftringen, Switzerland), that was homogeneously applied to the soil surface. In the stained preferential flow paths, concentrations of SOC and total N were 15 to 75% higher than in the soil matrix. The total increase of SOC in preferential flow paths ranged from 740 to 960 g C m−2 in four individual soil plots. Values of δ13C and δ15N were lowest in tree leaves and in the forest floor, and increased with soil depth, thus with the degree of decomposition of SOC. In the mineral soil, preferential flow paths were significantly depleted in 13C by 0.15 to 0.4‰ as compared with the soil matrix. The δ15N values increased with soil depth from 0.9 to 4.7‰ in the preferential flow paths and from 0.5 to 6‰ in the soil matrix. Adding a highly enriched 15N‐tracer homogeneously to the soil surface showed a higher recovery of 15N in the soil and in the fine roots sampled from preferential flow paths than in those sampled from the soil matrix. Our results suggest that in preferential flow paths, SOC is younger and N cycling is more rapid than in the soil matrix.
A technique to facilitate diffusions for nitrogen‐isotope analysis by direct combustion
Authors: Moran K. K. , Mulvaney R. L. , Khan S. A.
Published: July 2010

A technique was developed that permits the use of boric acid‐indicator solution in carrying out diffusions for inorganic 15N analysis of soil extracts by direct combustion, so as to eliminate the need for a separate quantitative determination. In this technique, the titrated sample is acidified with 2.5 M KHSO4 and subsequently treated with methanol to remove H3BO3 The NH+4‐N is dissolved in 1 mL of deionized water, concentrated after transfer to a microcentrifuge tube, and freeze‐dried in a tin capsule. Isotope‐ratio analyses were accurate to within 5% when diffusions were performed on 100 to 1000 μg of NH+4‐N (0.2–10 atom % 15N), whereas errors of 8 to 17% occurred with 25 to 50 μg of labeled N, even after correction for isotopic dilution by atmospheric NH3 The technique described permits 15N analysis of any form of N that can be recovered by H3BO3 diffusion of soil, soil extracts, soil hydrolysates, Kjeldahl digests, water, or wastewater.
Soil Consistence and Structure as Predictors of Water Retention
Authors: Rawls W. J. , Pachepsky Ya. A.
Published: July 2010

It is impractical to measure water retention for large‐scale hydrologic, agronomic, and ecological applications or at the design stages of many projects; therefore, water retention estimates are often used. Field soil descriptions routinely include structure and consistence characterization. The objective of this work was to use the National Resource Conservation Service (NRCS) database to evaluate the potential for structural and consistence properties to serve as predictors of soil hydraulics properties. Total of ≈2140 samples were found that had (i) values of water contents at −33 kPa and −1500 kPa, (ii) structure characterized with grade, size, and shape, (iii) consistence characterized with dry and moist consistency, stickiness, and plasticity, and (iv) textural class determined in the field and from lab textural analysis. Because structural and consistence parameters were represented by categories rather than numbers, regression trees were used for recursive partitioning of the data sets into groups to decrease overall variability measured as the sum of squared errors within groups. Plasticity class, grade class, and dry consistency class were leading predictors of water retention at both −33 kPa and −1500 kPa matric potentials. The accuracy of estimates from structural and consistence parameters was lower than from textural classes. Using soil structural and consistence parameters along with textural classes provided a small, although significant improvement in accuracy of water retention estimates as compared with estimation from texture alone. Soil structural and consistence parameters can serve as predictors of soil water retention because those parameters reflect soil basic properties that affect soil hydraulic properties.
Accounting for Soil Spatial Autocorrelation in the Design of Experimental Trials
Authors: Fagroud M. , Van Meirvenne M.
Published: July 2010

Soil heterogeneity complicates the design and analysis of field experiments. Block designs were developed for this purpose. However, the analysis of experimental results supposes that the residuals from the treatment are spatially independent and that within block variation is random. Experience indicates that this rarely is the case in field experiments, because of the strong spatial autocorrelation of soil properties. This paper applies geostatistical tools, such as variogram analysis and conditional stochastic simulation, to investigate the optimal experimental plot size and shape and to decide which experimental design is to be preferred. The methodology is illustrated using a case study of water‐use efficiency under semiarid conditions in Morocco. It was found that under these conditions an experiment with 16 treatments would use best a plot size of 4 by 8 m oriented north‐south, configured according to an incomplete block design with 8 plots per block oriented in two rows in the east‐west direction.
Effect of Carbonate on the Adsorption of Selenate and Sulfate on Goethite
Authors: Wijnja H. , Schulthess C. P.
Published: July 2010

Although it is generally recognized that goethite surfaces present in natural environments have carbonate species adsorbed, knowledge of their effect on the reactivity of goethite toward other anions remains limited. Accordingly, the effect of CO3 on the adsorption of SeO4 and SO4 on goethite is determined. Carbonate promotes the adsorption of SeO4 and SO4 between pH 6 and 8. The maximum effect occurs at relatively low CO3 concentrations (0.2 mM), and the promotive effect decreases and eventually becomes competitive with further increase in CO3 adsorption. Acetate (AcO) and formate also appear to promote adsorption of SeO4 and SO4. Based on existing Fourier transformed dsorption of SeO4 and SO4 Based on existing Fourier transformed infrared (FTIR) spectroscopic data and new electrophoretic mobility data, CO3 may promote the adsorption of other oxyanions by forming extra reactive protonated sites that coexist with the adsorbed CO3. Acetate and formate presumably interact through the same mechanism. Goethite surfaces present in natural environments may have substantial amounts of CO3 adsorbed. Depending on the CO3 levels, this may enhance, decrease, or have a neutral effect on the adsorption of moderate affinity anions such as SeO4 and SO4. Accordingly, the combined effects of promotive and competitive interactions may render CO3 less competitive overall than was commonly presumed. Similarly, the presence of AcO and formate may be less competitive with other anions due also to their promotive interaction effect.
Diffuse Double‐Layer Models, Long‐Range Forces, and Ordering in Clay Colloids
Authors: McBride M. B. , Baveye P.
Published: July 2010

The modern view of colloidal particle behavior in water is based on the DLVO (Derjaguin‐Landau‐Verwey‐Overbeek) theory, which hypothesizes strictly repulsive long‐range interactions among charged particles. However, numerous phenomena of colloidal behavior, some recently discovered, cannot be explained quantitatively or qualitatively by this theory. An alternative description of the fundamental forces involved in the formation of dispersions and gels was outlined in 1938 by Langmuir, and further developed theoretically by Sogami, Ise, and Smalley. This model, unlike DLVO, hypothesizes a long‐range Coulombic attractive force countering osmotic repulsion, which may explain experimentally confirmed multiparticle phenomena such as long‐range attraction and transitions among ordered (liquid crystalline) and disordered phases of colloidal suspensions. The key concepts of Sogami–Ise theory and its experimental support are reviewed in the present article. This review begins with an analysis of the extent to which dynamic (Brownian) motion and interparticle steric hindrance influence the macroscopic properties of clay dispersions and gels. It is shown that the covolume theory of Onsager in some cases could explain the existence of apparent long‐range interparticle interactions, and phase transitions between ordered and disordered states in colloidal dispersions, without invoking long‐range forces. Nevertheless, in situations where the composition of the electrolyte solution influences the observed interparticle interactions, the experimental evidence for long‐range attraction among charged colloidal spheres points to a force that is fundamentally electrostatic in nature, of the type envisioned by Langmuir. After consideration of all experimental and theoretical results to date, it is concluded that the DLVO theory adequately describes the repulsive interaction between isolated like‐charged particles, whereas a long‐range attractive force is needed to explain multiparticle interactions in suspensions under conditions of low electrolyte concentration and high particle charge.
A pH‐Dependence Implicit Formulation of Cation‐ and Anion‐exchange Capacities of Variable‐charge Soils
Authors: Katou Hidetaka
Published: July 2010

Cation‐ and anion‐exchange capacities (CEC and AEC) of variable‐charge soils are often expressed as a function of pH and the electrolyte concentration. A difficulty following this formulation is that changes in pH with time and space must be computed precisely if ion transport is to be predicted. In this paper, an alternative formulation of CEC and AEC is presented in which pH does not appear explicitly. The formulation is based on the notion that, unless H+ or OH− is added, changes in the total cation adsorption, Qcat (= CEC), and the total anion adsorption, Qan (= AEC), in response to a change in the total electrolyte concentration, C, are nearly equivalent. This means that the net surface charge remains virtually constant and leads to an equation that relates d[H+]/dC to partial derivatives of Qcat and Qan with respect to [H+] and C. Using this relation, we show that, if the exchange capacities are expressed by Qcat = kcat[H+]−acatCbcat and Qan = kan[H+]−aanCban, the change in Qcat (or Qan) with C in a soil saturated with monovalent ions is described by an ordinary differential equation which does not contain pH as a variable. The Qcat–C relations predicted by solving the equation closely agreed with those by the conventional method in which pH‐dependent adsorption, mass balance, and electroneutrality equations were solved simultaneously. The advantage of this approach is that once the adsorption parameters are known, the transport equation for H+ need not be solved in predicting transport of electrolyte ions in soil.
Surface Soil Physical Properties After Twelve Years of Dryland No‐Till Management
Authors: Shaver T. M. , Peterson G. A. , Ahuja L. R. , Westfall D. G. , Sherrod L. A. , Dunn G.
Published: July 2010

Water is the principle limiting factor in dryland cropping systems. Surface soil physical properties influence infiltration and cropping systems under no‐till management may affect these properties through residue addition. The objectives of this study were: (i) to determine how cropping intensity and topographic position affect soil bulk density, porosity, sorptivity, and aggregate stability in the surface 2.5 cm of soils at three eastern Colorado sites; and (ii) to relate these properties to crop residue returned to the soil surface. No‐till cropping systems had been in place on three slope positions, at three sites, for 12 yr prior to this study. Wheat (Triticum aestivum L.)‐corn (Zea mays L.)‐fallow (WCF) and continuous cropping (CC) systems were compared with wheat‐fallow (WF) on summit and toeslope positions at two sites (Sterling and Stratton), and at the third site (Walsh) wheat‐sorghum [Sorghum bicolor (L.) Moench]‐fallow (WSF) replaced WCF. Cropping systems (CC and WCF or WSF) that returned more crop residue decreased bulk density and increased total and effective porosities compared with WF. Site and slope positions that produced more crop residue also improved these properties. However, sorptivity developed no significant differences as a result of cropping system. Macroaggregates made up a higher percentage of total aggregates in CC and WCF or WSF compared with WF in proportion to residue added and were also a function of clay content of the soil at different sites and slope positions. These factors enhance the potential for greater infiltration and hence greater water availability for crops.
Soil Compaction Effects on Growth of Young Ponderosa Pine Following Litter Removal in California's Sierra Nevada
Authors: Gomez A. , Powers R. F. , Singer M. J. , Horwath W. R.
Published: July 2010

Increased use of heavy equipment and more frequent entry into forest stands has increased the potential for soil compaction and decreased productivity. We examined compaction and tree growth relationships on three California soils of contrasting textures (clayey, loamy, and sandy loam) on plots from which the organic soil horizon had been removed. Compacted and noncompacted treatments were compared. Changes in bulk density (Db), soil strength, and total porosity, measured during the growing season, were greatest in the 15‐ to 30‐cm depth at all sites. Bulk density increases were greatest in the loamy soil (30%) and least in the sandy loam (23%). Total porosity decrease in the upper 45 cm averaged 20, 9, and 13% for the clay, loam, and sandy loam textures, respectively. In the 30‐ to 45‐cm soil depth, compacted soils reached critical water potentials (<−1.5 MPa) 50 d sooner in the loam and 67 d sooner in the clay. In the sandy loam, compaction extended the period of plant‐available water for 86 and 48 d in the 1‐ to 15‐ and 15‐ to 30‐cm soil depths. Midday stem water stress was greater for trees in compacted plots of loamy and clayey textures, but less on sandy loam. Soil compaction did not reduce tree growth universally in these 3‐ to 8‐yr‐old plantations. Effects were detrimental, insignificant, and beneficial for clayey, loamy, and sandy loam soils, respectively. Results show that compaction effects depend strongly on soil texture and soil water regime. Soil physical values, per se, are not always reliable criteria for evaluation.
Formulating the Charge‐distribution Multisite Surface Complexation Model Using FITEQL
Authors: Tadanier Christopher J. , Eick Matthew J.
Published: July 2010

Sorptive interactions at the solid–water interface strongly influence the bioavailability of many important nutrient oxyanions and trace contaminant metals in both natural and engineered settings. Recently, the charge‐distribution multisite complexation (CD‐MUSIC) model has been developed to model ion adsorption behavior on variable‐charge minerals. Although this model shows great promise, its use has been limited by lack of incorporation into commonly used computer codes. In this study formulation of the CD‐MUSIC model in the surface complexation modeling program FITEQL 4.0 is described, and demonstrated using Cu2+‐ and orthophosphate (Pi)‐goethite adsorption data. Mass‐action and mass‐balance expressions for Cu2+ and Pi adsorption on goethite were developed using a combination of monodentate and bidentate surface species. Pauling's rules were used to determine the charge of surface adsorption sites and adsorption site density (nm−2) was calculated from crystallographic considerations. Electrostatic component coefficients in the mass‐balance expressions were adjusted to reflect the actual charge of goethite adsorption sites, thereby satisfying both the local charge balance for adsorbed species and the global charge balance of the system as a whole. FITEQL 4.0 was used to determine the best‐fit equilibrium constants for the Cu2+ and Pi surface adsorption mass‐action expressions, and the associated speciation of adsorbed ions. The speciation of adsorbed Cu2+ ions was dominated by a single monodentate surface species; whereas, two monodentate and one bidentate surface species were required to adequately describe Pi adsorption. Formulating the CD‐MUSIC model as outlined here provides a thermodynamically, electrostatically, and crystallographically consistent approach for solving surface adsorption equilibrium problems with FITEQL.
Organic carbon at soil particle surfaces—evidence from x‐ray photoelectron spectroscopy and surface abrasion
Authors: Amelung Wulf , Kaiser Klaus , Kammerer Gerd , Sauer Gustav
Published: July 2010

This study aimed at investigating the potential of x‐ray photoelectron spectroscopy (XPS) for investigating soil organic matter at secondary soil particles. The XPS was applied to microaggregates of the A horizon of a Typic Haplustoll (<20‐μm equivalent diameter, >53‐μm maximum real diameter) and to the fine‐earth fraction (<2 mm) of the Bs horizon of a Typic Haplorthod. Carbon and N, as well as Si (both samples), Ca (Haplustoll), and Al (Haplorthod) were detected. Removing the particle surface layer (<50 nm) by bombarding with Ar+ resulted in a strong reduction of the signals of C and N, while those attributed to inorganic components increased relatively. Consequently, in both soils, organic matter was concentrated at the surface of soil aggregates. We conclude that Ar+ sputtering followed by XPS analysis is a useful tool in identifying the accumulation of elements at the surfaces of soil particles.
The Effects of Microdrip and Conventional Drip Irrigation on Water Distribution and Uptake
Authors: Assouline S.
Published: July 2010

Drip irrigation at a rate close to plant water uptake necessitates low application rates (microdrip), which affect soil water regime and plant response. This study compare the effect of three emitter discharges, 0.25, 2.0, and 8.0 L h−1, on different aspects of the water regime in daily drip irrigated corn (Zea Mays L.), relying on field observations and numerical simulations. Field observations show that microdrip irrigation (i) tends to increase yield although this was not statistically significant under the experimental conditions; (ii) induces higher relative water content values in the 0‐ to 0.30‐m depth layer, and lower ones in the 0.60‐ to 0.90‐m layer. Numerical simulations, carried out using HYDRUS‐2D, show that microdrip irrigation led to the smallest wetted volume with the least extreme water content gradients both in the horizontal and the vertical axes. A saturated zone below the emitter was obtained only for the 8.0 L h−1 discharge. Comparing water content distributions with depth at the end of the application of the same amount of water close to the emitter, the driest profile is obtained for the lowest application rate. However, when compared at solar noon representing the time of the highest plant water demand, the upper 0.20‐m layer of the soil irrigated at the lowest rate was the wettest. Microdrip irrigation has reduced the dynamic changes in the water content during the day in the most active part of the root zone. It also caused the smallest reduction in the simulated water uptake relative to the potential value.
Macroaggregate Characteristics in Cultivated Soils after 25 Annual Manure Applications
Authors: Whalen Joann K. , Chang Chi
Published: July 2010

Agricultural management practices that alter the soil organic matter (SOM) content are expected to cause changes in soil stability and aggregation. Animal manure is a source of organic matter (OM) that has been demonstrated to increase macroaggregate formation and stability. The objectives of this study were to determine how long term cattle manure applications to a calcareous Haploboroll clay loam (Lethbridge, AB, Canada) affected aggregate size distribution, the total C, N, and P content of aggregate size fractions, and water‐stable aggregates. Beef cattle manure applied at rates >30 Mg ha−1 yr−1 under dryland production and >60 Mg ha−1 yr−1 to soils under irrigation resulted in fewer dry‐sieved aggregates >7.1 mm and more dry‐sieved aggregates between 0.47 and 1.2 mm in the 0‐ to 5‐cm depth, compared with unamended soils. The dry‐sieved aggregate fractions between 0.47 and 1.2 mm include the <0.84‐mm fraction that has been associated with increased susceptibility to wind erosion in the Canadian semiarid prairies. There was more total C, N, and P in all dry‐sieved aggregate fractions of soils receiving >30 Mg manure ha−1 yr−1 than unamended soils, and dry‐sieved aggregates between 0.47 and 2.0 mm tended to have the highest C, N, and P contents. Water aggregate stability was higher in irrigated than dryland soils, but did not improve with increasing manure application rates. Dispersing agents in the cattle manure appear to have destabilized the larger soil macroaggregates.
Effect of Land Use on Soil Degradation in Alpine Grassland Soil, China
Authors: Wu Ronggui , Tiessen H.
Published: July 2010

Grassland soils in Northern China are being seriously degraded under cultivation and grazing. This study investigated the impacts of land use on soil erosion and soil fertility in alpine grassland of China. Land uses included three levels of pasture degradation, lightly (LDP), moderately (MDP), and heavily degraded pasture (HDP) classified based on vegetation cover, and cultivated fields ranging from 1 to 50 yr of cultivation. Soil samples were collected from 18 sites at seven locations in Chernozemic soils between elevations of 2600 to 3000 m. Soil erosion was estimated by 137Cs radioactivity. When pasture was heavily degraded, 137Cs activity was significantly reduced, and organic C (OC), total N, and cation‐exchange capacity declined by 33, 28, and 18% respectively. Cultivation of grassland worsened soil erosion, and after 8‐, 16‐, and 41‐yr cultivation soil OC decreased by 25, 39, and 55%, respectively. Regionally, 59% of OC was lost within 30 to 50 yr of cultivation. There were concomitant losses of total N and exchange capacity. On cultivated soils, soil erosion and mineralization were equally responsible for organic C losses. Pasture degradation and cultivation also caused changes in soil P. Mineralization of organic P, incorporation of subsoil by tillage following erosion, and fertilization increased levels of Ca‐P in cultivated fields. This study indicated that grassland degradation and cultivation caused not only severe soil erosion, but also fertility decline and chemical changes of P dynamics.
Factors Contributing to the Tensile Strength and Friability of Oxisols
Authors: Imhoff S. , da Silva A. Pires , Dexter A.
Published: July 2010

Tensile strength (TS) and friability (F) are considered useful indicators of soil structural quality. This study hypothesized that TS and F are strongly influenced by soil intrinsic properties in some Oxisols. This research was conducted on soil samples collected from a sugarcane (Saccharum officinarum L.) farm and sampling sites (n = 25) were located along an Oxisols catena. The transect crossed three soil types: clayey Rhodic Hapludox; loamy Typic Hapludox, and sandy Typic Hapludox. Each sample comprised of 35 aggregates collected from the top layer. Tensile strength, F, particle‐size distribution, organic matter (OM), crystalline oxides, and poorly crystalline oxides were measured. Multiple regression analysis showed that TS was positively related (R2 = 0.92) with clay + silt (CS) content and OM, and that poorly crystalline Fe oxides were the constituent of CS fractions that most contributed to TS. Results also indicated that the soils were highly friable, with the crystalline Fe forms being positively related with soil F.
Rapid Analysis of Hog Manure and Manure‐amended Soils Using Near‐infrared Spectroscopy
Authors: Malley D. F. , Yesmin L. , Eilers R. G.
Published: July 2010

Application of hog (Sus domesticus) manure to agricultural land converts waste to fertilizer. Nevertheless, matching nutrients in highly variable manure to soil or crop needs requires analytical capability that is ideally field portable and cost‐effective. This study explored using rapid nondestructive near‐infrared spectroscopy (NIRS) to analyze nutrients in hog manure and receiving soil. Spectral data in the visible and near‐infrared (NIR) region (400–2500 nm) from manure samples were correlated with chemical analytical data from the same samples using multiple linear regression statistics to develop calibrations for the prediction of future unknown samples. For 64 manure samples from seven manure storage facilities, r2 between NIR‐predicted values and chemically measured values was 0.93 to 0.99 for NH4–N, total dissolved N (TDN), suspended N, soluble reactive P (SRP), total dissolved P (TDP), suspended P, suspended C, Na, and Mg. For K, Ca, conductivity, and pH, r2 was >0.80. Subsequent analysis of 75 samples from 25 facilities gave similar or slightly less successful results. Soil samples collected before and following application of manure were scanned in a field‐moist state and after drying. For field‐moist soil, r2 for N, organic matter, Mg, and moisture was >0.84; for SO4–S was 0.7. For dry soil, results were similar for N and better for Mg SO4–S, Ca, and K. Near‐infrared spectroscopy has potential to predict some nutrient and salt concentrations in manure rapidly and without sample preparation. It can determine moisture, organic matter, total N, and Mg in field‐moist or dry soil and SO4–S, Ca, and possibly K in dry soil.
Competitive Sorption of Arsenate and Phosphate on Different Clay Minerals and Soils
Authors: Violante Antonio , Pigna Massimo
Published: July 2010

Sorption and desorption of AsO4 on or from different soil components may have a dominant role in regulating As mobility in soils. The objectives of this work were to provide information on the factors that influence the competitive sorption of AsO4 and PO4 in soil. We studied the competitive sorption of PO4 and AsO4 on selected phyllosilicates, metal oxides, synthetic organo‐mineral complexes, and soil samples as affected by pH (4.0–8.0), ligands concentration, surface coverage of the oxyanions on the samples and the residence time. We found that Mn, Fe, and Ti oxides and phyllosilicates particularly rich in Fe (nontronite, ferruginous smectites) were more effective in sorbing AsO4 than PO4 In fact, by adding AsO4 and PO4 as a mixture (AsO4/PO4 molar ratio of 1) more AsO4 than PO4 was usually sorbed on birnessite, pyrolusite, goethite, nontronite, and ferruginous smectite, but more PO4 than AsO4 was sorbed on noncrystalline Al precipitation products, gibbsite, boehmite, allophane, and kaolinite. For example, at pH 5.0 the sorbed AsO4/sorbed PO4 molar ratio (rf) was 1.81 for birnessite, 1.05 for nontronite, but was only 0.45 for kaolinite and 0.14 for allophane. For montmorillonite, illite, and vermiculite the rf values were slightly <1. For soil samples, particularly rich in kaolinite, halloysite, allophane, and containing relatively large amounts of organic C, the rf values were usually much <1. For all the samples, the rf values increased by decreasing the pH and with the residence time of the oxyanions. The sorption of AsO4 (or PO4) on goethite and gibbsite decreased by increasing the initial PO4/AsO4 (or AsO4/PO4 molar ratio) up to 2.0. However, PO4 inhibited AsO4 sorption more on gibbsite than on goethite, whereas AsO4 prevented PO4 sorption more on goethite than on gibbsite. The data reported in this paper suggest that the mobility, the bioavailability, and the toxicity of As in soil environments may be greatly affected by the nature of soil components, pH, presence of anions (PO4), and residence time.
Continuous Multiple Measurement of Soil Redox Potential Using Platinum Microelectrodes
Authors: van Bochove Eric , Beauchemin Suzanne , Thériault Georges
Published: July 2010

Redox potential (EH) measurement is a reading of voltage difference between a working electrode such as a Pt electrode and a reference electrode inserted into the soil or various substrates. This study was conducted to develop a method for continuous, autonomous, and multiple EH measurements using Pt microelectrodes connected to a data logger. A preliminary field experiment was carried out to assess the long‐term viability of Pt microelectrodes installed in situ. A second experiment was conducted in the laboratory to test an interface designed to allow the stabilization of EH measurements. The Pt microelectrodes and reference electrode showed reliable readings during the field trial and generally tested viable at the end of the four month experiment. However, discrepancies between logged EH measurements and manually stabilized readings, particularly under moderate reductive conditions, emphasized the necessity to adapt the principle of manually stabilized readings to the use of a data logger. Laboratory data obtained from pairs of Pt microelectrodes and reference electrodes connected to a new homemade interface confirmed that instantaneous logged measurements led to the underestimation of EH values by 140 mV in the critical and unstable range of 0 to 200 mV. Continuous, multiple measurements of stabilized EH using Pt microelectrodes is now feasible using a stabilization interface placed between the microelectrode and the data logger.
Equations for Predicting Soil Organic Carbon Using Loss‐on‐Ignition for North Central U.S. Soils
Authors: Konen Michael E. , Jacobs Peter M. , Burras C. Lee , Talaga Brandi J. , Mason Joseph A.
Published: July 2010

Samples of 255 noncalcareous A, Ap, and AB horizons from selected major land resource areas (MLRA) in the north central USA were used to develop equations for predicting organic C content, as determined with a Leco C analyzer, from weight loss‐on‐ignition (LOI). Organic C concentrations of the samples ranged from 1.09 to 114.6 g kg−1Within each MLRA, strong linear relationships were observed between LOI and organic C measured by the Leco instrument, withr2ranging from 0.94 to 0.98. Predictive equations developed by least‐squares regression were significantly different for individual MLRA's. Loss‐on‐ignition is a rapid, inexpensive, and accurate method for estimating organic C concentration in soils of the north central USA. We recommend that unique predictive equations be developed for individual soil‐geographic regions.
Assessing Soil Moisture Regimes with Traditional and New Methods
Authors: Costantini Edoardo A. C. , Castelli Fabio , Raimondi Salvatore , Lorenzoni Paolo
Published: July 2010

Soil moisture regime classes are required by U.S. soil taxonomy and other classification systems. Soil moisture regimes are based on long‐term daily data of soil water content, which are as a rule estimated by means of models. International Commitee on Soil Moisture and Temperature Regimes (ICOMMOTR) has proposed classifying pedoclimate on the basis of biweekly water potential. This study was conducted to validate the use of the Erosion‐Productivity Impact Calculator (EPIC) model in assessing soil water content of experimental fields placed in different European pedoclimatic conditions, to compare the pedoclimatic classification obtained with EPIC with those produced by the traditional Billaux and Newhall models, and to evaluate the results attained with the ICOMMOTR methodology. The trial was carried out over a 5‐yr period in four experimental farms. The soil water content of a meadow was measured weekly or biweekly, at 0.15‐ and 0.75‐m (or 0.45‐m) depths. The EPIC model results were compared with measured data and submitted to statistical analysis of accuracy. Predicted daily soil water from EPIC was utilized to classify the soil moisture regimes following the requirements of U.S. soil taxonomy. The traditional Billaux methodology led to an overestimation of the presence of the xeric class whereas the Newhall method overrated the ustic soil moisture regime. The ICOMMOTR classification methodology was less affected by crop and by year variability than all the other methods and performed better in differentiating the soil moisture regimes of the four study sites.
Hydraulic and Physical Properties of Stony Soils in a Small Watershed
Authors: Sauer Thomas J. , Logsdon Sally D.
Published: July 2010

The presence of rock fragments in soil layers can have a profound impact on measured hydraulic properties. Variation of surface soil hydraulic properties influences the amount, distribution, and routing of overland flow. The objective of this study was to assess the effect of rock fragments and soil texture on infiltration, hydraulic conductivity, and related physical properties in soils of a small watershed in northwestern Arkansas. Single‐ring and tension infiltrometer measurements at three pressure heads (h = −0.03, −0.06, and −0.12 m) were completed on the surface soil layer at 42 sites along three transects crossing the watershed. Upland (Nixa, loamy‐skeletal, siliceous, active, mesic Glossic Fragiudults) and side slope (Clarksville, loamy‐skeletal, siliceous, semiactive, mesic Typic Paleudults) soils had significantly less rock fragments, lower infiltration rates (i), and lower hydraulic conductivities (K) at and near saturation compared with the valley bottom soil (Razort, fine‐loamy, mixed, active, mesic Mollic Hapludalfs). Average infiltration rate at h = −0.03 m for all soils was only 9% of the ponded value suggesting that pores >1 mm in diameter dominated water flow under saturated conditions. At saturation, hydraulic properties tended to increase with rock fragment content while, at h = −0.12, the opposite was true. It is hypothesized that the source of rock fragments (weathering in place vs. colluvial and alluvial origin) and contact with the surrounding fine‐earth fraction influence water flow by affecting hydraulic continuity near fragment surfaces. These relatively subtle morphological factors may have a disproportionate impact on water flow under near‐saturation conditions in these soils.
Measuring and Understanding Carbon Storage in Afforested Soils by Physical Fractionation
Authors: Six J. , Callewaert P. , Lenders S. , De Gryze S. , Morris S. J. , Gregorich E. G. , Paul E. A. , Paustian K.
Published: July 2010

Forested ecosystems have been identified as potential C sinks. However, the accuracy of measurement and understanding of the underlying mechanisms for soil organic C (SOC) storage in forested ecosystems needs to be improved. The objective of this study was to use aggregate and soil organic matter (SOM) fractionation techniques to identify SOC pools that preferentially stabilize SOC in the long term and elucidate SOC sequestration mechanisms in forested soils. At two sites (Wildlife area, Ohio and Kemptville, Ontario) representing two different soils (Hapludalf and Hapludoll), we sampled soils under agriculture, afforestation, and forest and separated them into aggregates. Different size classes of intra‐aggregate particulate organic matter (iPOM) fractions were isolated by density flotation, dispersion, and sieving. At both sites, aggregation and whole SOC content were greater in the forested than in the agricultural ecosystems. The greater aggregation in forested ecosystems resulted in greater iPOM C concentrations, especially the iPOM C fractions associated with microaggregates (53–250 μm) and microaggregates occluded within macroaggregates (mM) (250–2000 μm). The sum of C in these fractions (microaggregate protected C) was 468 ± 29, 696 ± 171, 673 ± 70 g C m−2 in the agricultural, afforested, and forested soils at Kemptville, respectively. The difference in the microaggregate protected C between the agricultural and the afforested soils accounted, on average, for 20% of the difference in whole SOC stocks between the soils. We conclude, SOC is stabilized for a relatively longer term within microaggregates formed in afforested and forest systems. Therefore, we suggest a new fractionation scheme to isolate this microaggregate associated SOC for assessing the impact of land use, land management, and climate change on C storage.
Enzyme Activities and Carbon Dioxide Flux in a Sonoran Desert Urban Ecosystem
Authors: Green Douglas M. , Oleksyszyn Michelle
Published: July 2010

Urban expansion into wildlands significantly changes soil processes such as nutrient cycling and organic matter processing. Knowledge of these changes is important so that the impact of urbanization on ecosystems may be assessed. We measured the activities of invertase, cellulase, and CO2 flux in mesiscape, xeriscape, and in remnant desert patches in a rapidly urbanizing south central Arizona Sonoran desert ecosystem. In this system, mesiscapes are irrigated watered lawns, xeriscapes include low water‐use vegetation, and desert remnants include undeveloped areas within the urban matrix. Invertase activity ranged from 2.4 to15 mg glucose equivalents (GE) g−1 24 h−1 Invertase activities in mesiscapes during January exceeded desert remnant sites by a factor of six and xeriscape sites by a factor of two. Cellulase activity ranged from 48 to 406 μg GE g−1 24 h−1 Cellulase activity in mesiscapes during January significantly exceeded desert remnant and xeriscape sites by a factor of two. Mesiscape soils were up to 18.4°C cooler than xeriscape soils and had the lowest average temperatures (20.7°C). The average temperature of desert remnant soils was 27.4°C. Over the study period, CO2 flux rates ranged from 0.212 to 1.760 g m−2 h−1 Maximum rates of CO2 flux rates occurred in the spring and summer, and flux rates were lowest during the winter months. Winter peaks of enzyme activity are attributed to the onset of dormancy in C‐4 grasses in the fall and establishment of winter lawns by homeowners.
Evaluation of Mehlich 3 as an Agri‐Environmental Soil Phosphorus Test for the Mid‐Atlantic United States of America
Authors: Sims J. T. , Maguire R. O. , Leytem A. B. , Gartley K. L. , Pautler M. C.
Published: July 2010

Laws and guidelines limiting P applications to cropland based on soil P exist in the Mid‐Atlantic USA because of water quality concerns. We evaluated Mehlich 3 (M3) as an environmental soil P test using 465 soils typical to the Mid‐Atlantic region and found M3‐P accurately predicted water soluble P (WSP), desorbable P (Fe oxide strip P [FeO‐P]), and total sorbed P (oxalate P). The M3‐P saturation ratio (M3 [P/(Al+Fe)]) was linearly related to the well‐established oxalate P saturation method (DPSox) and a M3 [P/(Al+Fe)] range of 0.10 to 0.15 corresponded to reported environmental limits for DPSox (25–40%). Rainfall simulation and column leaching studies showed M3 [P/(Al+Fe)] predicted runoff and leachate P concentrations better than M3‐P. We suggest consideration of the following approach now used in Delaware for agri‐environmental interpretation of M3‐P and M3 [P/(Al+Fe)]: (i) Below optimum (crop response likely; M3‐P ≤ 50 mg kg−1; M3 [P/(Al+Fe)] < 0.06); (ii) Optimum (economic response to P unlikely, recommendations for P rarely made; M3‐P = 51–100 mg kg−1; M3 [P/(Al+Fe)] = 0.06–0.11); (iii) Above Optimum (soil P will not limit crop yields, no P recommended; M3‐P > 100 mg kg−1; M3 [P/(Al+Fe)] > 0.11); (iv) Environmental (implement improved P management to reduce potential for nonpoint P pollution—in Delaware M3‐P > 150 mg kg−1; M3 [P/(Al+Fe)] > 0.15 is now used). (v) Natural Resource Conservation (no P applied even if the potential water quality impact is low to conserve P, a finite natural resource).
Measuring Agronomic and Environmental Soil Phosphorus Saturation and Predicting Phosphorus Leaching with Mehlich 3
Authors: Maguire R. O. , Sims J. T.
Published: July 2010

The role that soil testing can play in identifying agricultural soils with an increased potential for P loss is an important topic. Our research compared the Mehlich 3 P saturation ratio (M3‐PSR) with the ammonium oxalate degree of P saturation (DPSox), and the M3‐PSR was then evaluated for predicting agronomic and environmental soil P saturation thresholds. Intact soil columns (15‐cm diam, 20 cm deep) and soil samples were collected from five soil series that ranged in soil texture, chemical properties, and Mehlich 3 P. The soils were analyzed for pH, organic matter (OM) and oxalate and Mehlich 3 extractable P, Al, and Fe. Each intact column was leached with the equivalent of 5 mm of rainfall and resulting leachate analyzed for P. Mehlich 3 extractable Al, Fe, and P were closely related to oxalate extractable Al, Fe, and P, although Mehlich 3 extracted only a small amount of Fe compared with oxalate. The M3‐PSRs, calculated as the molar ratios of Mehlich 3 extractable P/[Al + Fe] (ratio I) and P/Al (ratio II), were well correlated to each other and to DPSox All three P saturation measurements showed a threshold or change point above which the concentration of P in column leachate increased rapidly. Both the agronomic optimum M3‐PSRs and the environmental limit suggested in the Netherlands for DPSox (25%) were below the observed change point. The M3‐PSR measured in a single Mehlich 3 extraction shows excellent promise for identifying soils that represent an increased risk for P leaching losses.
GAS TRANSPORT OF VOLATILE ORGANIC COMPOUNDS IN UNSATURATED SOILS
Authors: Kim Heonki , Lee Seungjae , Moon Ji-Won , Rao P. Suresh C.
Published: July 2010

Knowledge of the gas transport of volatile organic compounds (VOCs) through unsaturated soils is important for understanding the fate of these contaminants. However, studies have not been performed for examining the retardation of VOCs, based on quantitative analyses of processes contributing to retardation as the function of water content during gas flow through unsaturated soils. No investigations have evaluated whether different factors that contribute to VOC retardation during gas transport have an additive effect, such that the sum of different effects can be used to predict overall transport velocity. A series of gas transport experiments was conducted in a soil column over a range of water contents, using a soil with low organic carbon content (approximately 0.1%), and tetrachloroethene (PCE) and 1,1,1‐trichloroethane (TCA) as representative VOCs. Three phase‐partitioning processes (partitioning into soil water, adsorption at the soil particles, adsorption at the air–water interface) were evaluated independently. The sum of retardation effects from these processes was then compared with the observed VOC retardation factors. Measured retardation factors for PCE and TCA were in good agreement with those predicted over the range of water contents (0.02–0.24) examined in this study, supporting the additive nature of different phase‐partitioning processes for the gas transport of VOCs in soils. Also, the relative contribution of each phase‐partitioning process to the total retardation of VOCs during gas transport was a strong function of water content.