bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymers as Soil Conditioners Under Consecutive Irrigations and Rainfall
Authors: Ben‐Hur M. , Faris J. , Malik M. , Letey J. 
Published: July 2010

AbstractLow water infiltration caused by crust formation during rain or sprinkler irrigation is a significant problem in some arid and semiarid regions. Polymers may be applied in irrigation water through a sprinkler system, but must be applied directly to the soil under rainfall conditions. The objectives of this rainfall simulator study were to: (i) determine the effect of drying of crusted vermiculitic soil on the subsequent crust properties and infiltration rate (IR) values, (ii) determine the effect of polymers applied at low concentration in irrigation water of two qualities on the IR under consecutive water applications, and (iii) determine the effectiveness of polymer application to the soil as would be required under rainfall conditions. Two cationic polysaccharide guar derivatives having a higher (HCCP) and a lower (LCCP) charge density and a polyacrylamide (PAM) with a low negative charge density were used in the study. Applications of polymers with the sprinkler water maintain IR in the order HCCP > LCCP > PAM > untreated. Except for PAM, the polymer applications were relatively ineffective in subsequent sprinkler applications with plain water applied with impact energy. The beneficial effects were preserved under water application without impact energy. Spraying concentrated polymer solutions on the soil surface was not effective in preventing crust formation by following rain events except for the case when LCCP was sprayed on in a CaCl2 solution. The results are explained on the basis of polymer adsorption and penetration into the soil surface layer and aggregates.
Modeling Potassium‐Calcium Exchange Isotherms in Soils
Authors: Dufey Joseph E. , Delvaux Bruno 
Published: July 2010

AbstractIon exchange equilibria involving K cannot be described by a constant selectivity coefficient for all surface compositions. The main reason is that the soil exchanger contains various types of sites with different affinities for K ions. This paper makes use of a multi‐site model, the main assumption of which is that the exchange reaction is governed by single values of the Vanselow selectivity coefficient, Kv, for each type of site. The simplest model—i.e., the two‐site model—is tested. Three parameters must be adjusted: the proportion of high and low selective sites, and the Kv's for these two classes of sites. Simulated K‐Ca exchange isotherms are shown, with various combinations of the parameters. The model has been adjusted to experimental K‐Ca exchange data, using a non‐linear regression procedure. A fair agreement between the experimental and calculated curves is obtained. As a consequence, this simple model proves to be a powerful tool for a quantitative description of exchange data involving K ions.
Use of Referential Coordinates in Deforming Soils
Authors: Baveye Philippe , Boast Charles W. , Giráldez Juan V. 
Published: July 2010

AbstractAnalysis of hydrological processes in deforming soils generally involves use of some form of a referential, or material, coordinate transformation. In the most commonly used of these relationships, there appear two macroscopic soil mass density factors, that associated with the configuration of the soil at a reference time t = 0, and that associated with its configuration at a later (arbitrary) time. In some previous work, the assumption was made that these bulk densities could be evaluated at the same space‐fixed point. In an illustrative application to dual‐energy gamma‐ray data on the swelling of a clay loam during infiltration, this approximation is shown here to predict vertical displacement values that are as much as 7 mm in excess of values obtained without the approximation. Moreover, the approximation fails to satisfy macroscopic mass balance. It is also shown that the direction, downward or upward, of the vertical displacement of macroscopic body‐points depends on the boundary condition used in the integration of the referential coordinate transformation; i.e., depends on whether the integration begins at the soil surface or at a point below the wetting front. Since these two integration pathways are mathematically equivalent, it is argued that a systematic comparison between results obtained using them can serve a useful purpose in detecting occurrences of lateral expansion or systematic errors in the experimental data.
Use and Hydrological Robustness of Time‐to‐Incipient‐Ponding
Authors: White I. , Sully M. J. , Melville M. D. 
Published: July 2010

AbstractBoth the use and hydrological robustness of time‐to‐ponding, tp, have been questioned recently. We examine these questions here for variable rainfall rates. Using a nondimensional analytic form for tp, we show that for rainfall rates, R, greater than about 1.5 times the saturated hydraulic conductivity, Ks, tp is relatively robust. Only in the region Ks ≤ R ≤ 1.5 Ks is tp sensitive to small changes in R/Ks. We also show a comparison between field measurements of tp using a rainfall simulator on a structurally unstable, sodic and saline gravelly silty clay loam and those predicted using the analytic expression and measured values of Ks and sorptivity determined under ponded conditions with disc permeameters. The good agreement found, together with the ease and reproducibility of the field measurements, indicate that both the determination and prediction of tp are soundly based provided R > 1.5 Ks. Finally, we use the analytic expression for tp in the inverse sense to determine the soil's sorptivity, hydraulic conductivity and characteristic mean pore size, a measure of soil pore structure, from values of tp, R and the steady state runoff during rainfall. These hydraulic properties agree well with those measured under a constant head. We conclude that tp is a useful and hydrologically robust property provided R(tp) > 1.5 Ks.
Carbazole Sorption by Surface and Subsurface Materials: Influence of Sorbent and Solvent Properties
Authors: Ainsworth C. C. , Zachara J. M. , Smith S. C. 
Published: July 2010

AbstractSorption of 9H‐carbazole was investigated from aqueous and co‐solvent solutions on soils with different physical and chemical properties. Sorption was nonlinear, but well correlated to the organic carbon (OC) content of the soils. The variability of the Freundlich adsorption constant (Kt), normalized to OC (Kfoc) is small between A horizons of two Mollisols and two Ultisols but increases to about 0.8 log units between C horizons of the Mollisols and Ultisols. This variability combined with the absence of linear partitioning leads to poor predictability by C reference partitioning based on octanol/water or water solubility parameters in the highly weathered soils. Differences in structure and type of the associated OC may be a factor affecting predictability. The presence of methanol and acetone induces a log‐linear decrease in carbazole sorption with mole fraction cosolvent. For a given solvent (i.e., MeOH, acetone) the log‐linear behavior is independent of sorbent properties and exhibits a common slope, thus attesting to the importance of the solvent interaction. In contrast, pyridine as a cosolvent is actively sorbed by some soils creating a more oleophilic surface and a tendency to increase carbazole partitioning to the soil surface.
A Continuous‐Flow Stirred Reaction Cell For Studying Adsorption In Suspensions
Authors: Miller D. M. , Miller W. P. , Sumner M. E. 
Published: July 2010

AbstractSolute sorption by inorganic colloids is currently studied using either batch or miscible displacement techniques, but continuous‐flow stirred reaction cells may represent a desirable alternative to these methods in certain situations. A practical limitation of current cell designs is the inadequate mixing effected by magnetic stirrers, which allows the sorbent to rapidly deposit onto the filter membrane. We have designed a continuous‐flow stirred reaction cell in which the suspension is efficiently and vigorously mixed by means of a two‐blade impeller powered by an electric motor. The impeller shaft is bearing‐mounted and sealed with a rubber O‐ring. The entire cell is water jacketed for temperature control. Joule heating appears to be insignificant at the impeller speeds required for mixing at flow rates of up to 60 mL h−1. Runs with orthophosphate solution and no adsorbent indicate that mixing is ideal. Data reduction is illustrated using a phosphate/goethite system.
Exchange Properties of an Argiustoll: Effects of Long‐Term Ammonium Nitrate Fertilization
Authors: Schwab A. P. , Ransom M. D. , Owensby C. E. 
Published: July 2010

AbstractSoil acidification can result from the application of high rates of ammonia‐based fertilizers, but little information is available concerning the effects of long‐term, annual applications at moderate rates. In this study, plots that were mapped as Smolan silt loam (fine, montmorillonitic, mesic Pachic Argiustolls), 1 to 4% slopes, containing an established stand of smooth bromegrass (Bromus inermis Leyss.) were fertilized continuously with rates of 0, 22, 67, 112, 157, and 224 kg N/ha for 40 yr, or for 20 yr followed by 20 yr without N fertilizer. The objective of this research was to determine the effects of such long‐term applications of NH4NO3 on exchange properties. In the continuously fertilized plots, pH and exchangeable Ca2+, Mg2+, and K+ decreased in the upper 20 cm of the soil, and neutral‐salt cation exchange capacity decreased in the upper 10 cm, whereas exchangeable Al (1 M KCl) and BaCl2‐triethanolamine (BaCl2‐TEA) extractable acidity increased. In all cases, significant changes were observed only when N application exceeded plant demand. Discontinuation of fertilization for 20 yr resulted in a significant, but incomplete, trend of the exchange properties toward values of the unfertilized soils. Thus, the acidification resulting from NH4 application, which occurred at even low application rates, was reversed somewhat after fertilization ceased.
Selection of Reference Plants and Methods for Estimating N2 Fixation in Mycorrhizal Leguminous Plants
Authors: Schoeneberger M. M. , Volk R. J. , Davey C. B. 
Published: July 2010

AbstractThe effects of plant species and mycorrhizae on reference plant suitability were examined with regard to estimating N2 fixation in two leguminous plants via the 15N isotope dilution technique (ID). Atom percent excess (A % E) 15N values of ryegrass (Lolium perenne L. ‘PennSinn’), nonnodulated big trefoil (Lotus pedunculatus Cav. ‘Marshfield’), and nonnodulated subterranean clover (Trifolium subterraneum L. ‘Mt. Barker’), each with or without mycorrhizae, were compared at fertilizer N rates of 10 and 100 kg N ha−1. Precision of the ID method was compared to the total nitrogen difference (ND) method. Atom percent excess 15N values of the reference plants had lower coefficients of variation than total N yields (mg plant−1), and were unaffected by mycorrhizal treatment. Overall shoot values of A % E 15N were similar in trefoil and ryegrass, but were lower in clover in the 100 kg N ha−1 fertilizer treatment. In roots, the A % E 15N values for clover were significantly larger than those for ryegrass. There were no differences between the values of N derived from the atmosphere (Ndfa) (percent and amount for shoot, root, and total plant) in clover, as estimated by the ID method, using nonnodulated clover and ryegrass as reference plants. Values for Ndfa (percent and amount), as estimated by the ND method, differed significantly from the ID values. The ND values were either smaller or larger than ID values, depending on N rate and inoculation treatment. In the 100 kg N ha−1 rate, the ND method resulted in negative values for root Ndfa. Given the similarity of A % E 15N shoot values in all three reference plants, and the insensitivity of Ndfa to the reference plant used for its calculation, ryegrass was found to be an appropriate reference plant for determining N2 fixation via the ID method in both big trefoil and subterranean clover.
Cultivated and Adjacent Virgin Soils in Northcentral South Dakota: II. Mineralogical and Micromorphological Comparisons
Authors: Blank R. R. , Fosberg M. A. 
Published: July 2010

AbstractCultivated and adjacent virgin soils [Williams (fine‐loamy, mixed, Typic Argiboroll) and variants of Williams] from northcentral South Dakota were compared, by horizon, to examine the effects of cultivation on mineralogical and micromorphological properties of the soils. Two major mineralogical differences were noted. Silt‐sized material from the Btk, Bk, and C horizons of a cultivated pedon had smaller calcite‐to‐dolomite peak‐height ratios, as determined by x‐ray diffraction, than similar horizons from a virgin pedon. These findings, combined with the results of additional experimentation, suggest calcite is being leached from Btk horizons and is accumulating in Bk horizons of cultivated pedons. The A, Bt, and Btk horizons of a virgin pedon had more subdued x‐ray peak intensities for the 001 spacing of smectite than similar horizons from a cultivated pedon. When similar horizons of a cultivated and a virgin pedon were compared, micromorphological differences were as follows: (i) the Ap horizon displayed less macroporosity, more diffuse and lighter‐colored organic glaebules, fewer and less pronounced microaggregates, and fewer surface coatings on sand‐sized particles; (ii) the Bt horizon from the virgin pedon had greater macroporosity; (iii) the Btk and Bk horizons of the virgin pedon contained more particles coated with and more composite particles bound with organo‐mineral material; (iv) a far greater proportion of voids were filled with black, opaque cutans in the Btk horizons of the cultivated pedons that, by electron microprobe analysis, was dominantly Si.
Partitioning of Clay‐Sized Minerals in Coastal Plain Soils with Sandy/Loamy Boundaries
Authors: Cabrera‐Martinez F. , Harris W. G. , Carlisle V. W. , Collins M. E. 
Published: July 2010

AbstractFour soils with sandy/loamy boundaries occurring at various depths were studied with respect to distribution of clay‐sized minerals within the soil matrix. Mineralogy of coarse and fine clay was determined by horizon using x‐ray diffraction. Also, mineralogy of clay from ped interiors vs. exteriors (coatings) was determined for the Bt horizon of one soil. Mineralogical differences in coarse‐clay distribution were observed with respect to location above or below the sandy/loamy boundary. Clay above the boundary was consistently high in hydroxy‐interlayered vermiculite (HIV) and quartz, regardless of depth to the boundary. One exception was the A horizon of a Spodosol, which consisted essentially of quartz; however, the Bh horizon of this soil (above the boundary) did contain appreciable HIV. Below the boundary, the upper Bt horizon exhibited an increase in kaolinite and a sharp decrease in quartz relative to overlying E or Bh horizons. A marked decrease in HIV below the upper Bt horizon was also evident. Fine clay contained more kaolinite and less HIV and quartz than did coarse clay, and exhibited less intra‐pedon variation. Possibly HIV comprises a greater proportion of the clay residue in eluvial horizons because of the greater size of its precursor, which could be mica, and subsequent resistance to translocation. The greater abundance of HIV in ped coatings relative to ped interiors suggests that some contemporary translocation of coarser clay from HIV‐dominated eluvial horizons has occurred along major voids between peds. The d001 peak shift with heat treatment for HIV was similar for all samples, suggesting that depth and landscape position have had little influence on degree of interlayer polymerization in these soils.
A Low Abrasion Crusher for Preparation of Air‐Dried Soils for Element Extraction
Authors: Kowalenko C. G. , Scobie B. S. 
Published: July 2010

AbstractA crusher was developed for mechanizing the preparation of air‐dried soil samples for nutrient extraction including metals. The crusher simulated manual crushing of samples with a rolling pin. All surfaces contacting the soil were plastic and the crusher could be thoroughly cleaned, minimizing the risk of sample contamination. Readily available materials were used to achieve low fabrication costs. The crusher used two rollers, rotating in opposite directions and the crushed sample was further processed by a vibrating plastic sieve. The pressure between the rollers was adjustable. The prototype crushed and sieved samples from a variety of soil types faster and with less effort than manually with a rolling pin. The conceptual approach offers a consistent and reproducible mechanized process of soil sample preparation for multiple element extraction purposes.
A Dilute Medium to Determine Population Size of Ammonium Oxidizers in Forest Soils
Authors: Donaldson Jennifer M. , Henderson Gray S. 
Published: July 2010

AbstractIncubation experiments using soils from mixed oak (Quercus sp.) stands showed accumulation of nitrate but standard most probable number (MPN) assays showed no NH4‐oxidizing bacteria were present. This led to a preliminary conclusion that nitrification in these soils must be heterotrophic. However, further incubation studies indicated that NH4‐N concentrations in standard MPN medium were too high for autotrophic NH4 oxidizers that are adapted to soils with low NH4‐N levels and exhibit low activities. Therefore, media with lower NH4‐N concentrations were tested against the standard MPN medium. Each medium was tested using both 1 mM phosphate buffer and deionized water as diluent to examine responses to small changes in buffer capacity. A 0.1 × medium used with deionized water diluent was found to best estimate populations of low‐activity NH4‐oxidizing bacteria present in soils with low NH4‐N concentrations.
Generalized Results from Crop Yield Model with Saline Waters
Authors: Warrick A. W. 
Published: July 2010

AbstractCrop yields as influenced by water quality and quantity are of immense interest in arid areas throughout the world. In this paper, earlier results are generalized for modeling crop yield under deficit irrigation with saline water. Linear yield response functions were used for both the amount of water utilized and response to salts. Results are presented in a compact table for a wide range of conditions for salinity, water and yield response parameters. Included in the analysis is the effect of variability of available water. Results are similar to those obtained when salinity is not a factor, in that more variability of available water generally leads to lower average yields. This relatively simple approach is believed applicable to many practical scenarios for which a lack of input parameters or need for expediency rules out more comprehensive modeling.
Phosphorus Behavior in Flooded‐Drained Soils. II. Iron Transformation and Phosphorus Sorption
Authors: Sah R. N. , Mikkelsen D. S. , Hafez A. A. 
Published: July 2010

AbstractEffects of flooding periods (FP), organic matter (OM) and temperature treatments during flooding on Fe transformation in flooded‐drained (FD) soils were studied on four soils representing wide variations in the effect of FD conditions on P sorptivity. The soils were extracted in sequence with ammonium oxalate at pH 6 (amorphous FeA) and at pH 3 (amorphous FeB), and with dithionite‐citratebicarbonate reagent (free Fe oxides). The amorphous FeA fraction increased with FP, OM treatment, and elevated temperature. In soils with low amorphous‐Fe to free‐Fe‐oxide ratio, both amorphous FeA and free Fe oxides increased at the expense of amorphous FeB as the FP increased. In soils with low amorphous‐Fe to free‐Fe‐oxide ratio, both amorphous Fe fractions (A and B) increased at the expense of free Fe oxides as FP increased. For all soils, the Fe transformation during soil flooding was accelerated by OM and high‐temperature treatments, both of which contributed to a decreased redox potential in the soil. Amorphous FeA fraction correlated well with P sorption under all combinations of OM and temperature in each soil, while other Fe fractions correlated well only under certain conditions. Results suggest that the nature and the magnitude of Fe transformations in these FD soils depend on interacting effects of FP, OM, and temperature.
Spectral Band Selection for Classification of Soil Organic Matter Content
Authors: Henderson Tracey L. , Szilagyi Andrea , Baumgardner Marion F. , Chen Chih‐chien Thomas , Landgrebe David A. 
Published: July 2010

AbstractNew instruments currently in design for Earth observational remote sensing from space offer promising advancements in the use of remote sensing for soil studies. Due to the enormous quantities of data generated by these high spectral resolution sensors, efficient use will only be feasible if new algorithms are developed to compress the data while maintaining information content. A spectral band selection algorithm is proposed to identify the important spectral bands for compression and classification of soil reflectance data. This algorithm was developed from the shape dominancy concept of Karhunen‐Loeve based optimal features. The high dimensional raw data were first transformed into much lower dimensionality by the derived spectral features. Canonical analysis was then used to transform the data under the maximal separability criterion into their final signal space where the data classification was performed. Soil data sets with and without stratification by soil order and climatic moisture zone were used to test the algorithm. The probabilities of correct classification of soil organic matter content using Landsat Multispectral Scanner (MSS) bands, Thematic Mapper (TM) bands, and the bands identified using the new band selection algorithm, were calculated and compared. The algorithm was successful in finding important spectral bands for soil organic matter content classification. The probabilities of correct classification obtained by using these bands were 0.850 and 0.883 for unstratified data sets, as compared to 0.600 to 0.640 for MSS bands and 0.640 to 0.653 for TM bands. Probabilities of correct classification for climate‐stratified data ranged from 0.910 to 0.980 using the calculated bands. The overall data compression ratio achieved using the algorithm was greater than 10 with no loss in classification accuracy.